May 27, 2016, Ontario – Corn planting is nearly complete in Ontario, and soybean planting isn't far behind, according to the latest field crop report from OMAFRA.
Planted acreage across the province is at about 90 per cent complete, with exception of some of the heavier soils in Essex and Lambton counties yet to be planted. Most of the corn acreage has emerged and is at the spike to first-leaf over stage with the most advanced corn at the two-leaf over stage. Corn has recovered from the frost injury of 10 days ago.
Some pre-side-dress nitrogen testing (PSNT) will begin next week (see Table 1, Nitrogen Recommendations Based on Nitrate-Nitrogen on http://fieldcropnews.com). Early soil nitrate testing has shown higher than expected soil nitrate levels considering the cool, dry weather thus far this spring.
Winter wheat is at the Zadok 37 to 55 (flag-leaf half emerged to head half emerged) stage, looking good in most areas of the province. Stripe rust infection spread last week from the southwest (Windsor to London) to Huron (Exeter) and Bruce County (Walkerton). Fields with strip rust tolerant varieties or were sprayed early at the T1 stage, have less pressure. Higher nighttime temperatures should slow the development and spread of strip rust (optimum 10 C to 20 C). Growers should continue to scout their fields and if stripe rust is a problem, growers should spray immediately but be aware of wheat stage. Once the wheat reaches boot stage (Zadoks 45), the application of products containing a strobilurin fungicide may increase the amount of mycotoxins in the grain.
As we approach the flowering stage (Zadok’s 59), the use of a T3 fungicide to control Fusarium head blight will also control many leaf diseases, such as stripe rust. Weather forecast and DONcast may assist to best co-ordinate need for FHB fungicide application at flowering.
Spring Cereals are now in the tillering stage (Zadok 26 to 30). Many annual weeds have emerged and growers should consider spraying.
Soybean planting about 80 per cent complete across the province, with the exception of only about 50 per cent planted in Essex and Lambton counties. Some emergence concerns in the drier areas on the lighter soils, particularly east of the 400 where soybeans were planted into dry soil.
Winter cereal rye is head half emerged stage. Forage quality drops rapidly as the crop matures past this stage.
Orchard grass is headed now and alfalfa is at the early bud stage. A few growers have begun harvest planning to take four cuts this season. Stands with a higher percentage of orchardgrass in the forage mix should be cut soon as quality drops rapidly as the orchardgrass matures.
Most of the planting is now complete. Conditions for emergence have been good. Flea beetle damage has been reported. Fields should be scouted now. This is also the time to set up monitoring traps for swede midge. The adult emergence peak is end of May to mid June. See infosheet for more information.
The planting of Azuki Beans started this past weekend. Edible bean growers will be planting this week. Remember to plant to moisture under the dry soil conditions.
Management of weeds will become the next priority in corn and soybeans if no pre-emergence herbicides have been applied. In soybeans, scout for weeds at around 10-14 days after planting because many annual weeds will be starting to emerge. Be mindful of environmental conditions at the time of applying post emergent herbicides that would increase the risk of off-target spray drift. In general off-target drift can be reduced when an applicator:
• sprays when wind speeds are light to moderate and moving away from the any nearby sensitive crop
• uses nozzles having the coarsest effective droplet size that will still achieve effective pest control
• reduces the distance between nozzle and target
Go to www.sprayers101.com/spray-drift for more specific details about sprayer modification to reduce the risk of off-target drift to sensitive high value crops.
Cleavers in field pea. Photo courtesy of Eric Johnson, U of S.
Field surveys across Western Canada are showing an increase in the presence of cleavers. Generally, the vast majority of populations have been identified in Saskatchewan; however in the 2010 weed survey in Alberta, cleavers ranked as the number three weed in canola and number one weed in pulses. Cleavers are difficult to control in many crops and can cause downgrading and reduced crop quality.
With funding from the Saskatchewan Canola Development Commission, Western Grains Research Foundation, Government of Saskatchewan Ag Development Fund, and multiple industry partners, researchers at the University of Saskatchewan (U of S) have just concluded a two-year study to help growers in managing cleavers in canola. They characterized the emergence and genetic characteristics of cleavers populations in Western Canada, which were believed to be two species: Galium aparine and G. spurium. Researchers also assessed the response of cleavers to potential new herbicides (in canola) such as quinclorac and clomazone, as well as their response to common canola herbicides such as glufosinate-ammonium and glyphosate to determine whether differences among populations existed.
In 2012 and 2013, field experiments were conducted at different locations in Saskatchewan, including Scott, Saskatoon and Rosthern (2014 only). Eight herbicide treatments were used in this experiment, including the herbicide standard for each canola system used alone and with the addition of quinclorac (tank-mix) and/or clomazone (preseed). At all sites, canola varieties (L130, 73-75 and 45H73), resistant to their respective herbicide system, were seeded into cereal stubble. Greenhouse dose-response experiments were also conducted to assess whether variability existed between populations in their response to herbicides.
“One of the most important findings from our research for management of cleavers in canola is that a portion of cleavers are emerging in both spring and fall, and that emergence timing of each of these fall and spring cohorts varied between years,” explains Christian Willenborg, assistant professor, department of plant sciences at the University of Saskatchewan. “Historically, cleavers were considered an obligate winter annual and generally emerged in the fall. However, our research confirms what growers and agronomists have been seeing: cleavers have largely responded to our cropping systems and, along with a shifting climate, are now emerging in both fall and spring. These differences suggest growers will need to pay close attention to emergence timing of this weed to ensure the small window for control is not missed.”
Another important outcome was that researchers successfully developed a molecular marker that could differentiate and characterize the cleavers species in the field. It has long been believed cleavers populations in fields across Western Canada are a mixture of both species. However, molecular analyses showed all sampled populations were in fact identified as G. spurium, or false cleavers. Although no G. aparine was found in the collected samples, it does not mean there is none present in fields across the Prairies. Willenborg adds that for growers, knowing populations are primarily one species, G. spurium, which is also the species that possesses resistance to Group 2 herbicides, is important because resistance will spread more quickly if all plants within the population are the same species.
One of the key recommendations resulting from the study is that growers will have to have a well-planned strategy for managing cleavers at different times in the rotation. “We found that in canola, spring emerging cleavers seem to emerge right after the crop is planted, and are often too large for some in-crop herbicide products, particularly those with a narrower application window such as the two-whorl or two- to four-whorl stage,” Willenborg says. “In some cases, such as the last couple of years, growers were unable to make a fall application because of either inclement weather or the timing of harvest. This can cause problems the following spring, as cleavers plants may be very large at this point and therefore difficult to control with pre-emergence herbicide applications. As well, some in-crop application timings have not been ideal because of the higher than usual moisture conditions.”
On the positive side, the results of the field study conducted over two years and at three sites showed that clomazone and quinclorac significantly reduced cleavers biomass and seed contamination and improved cleavers control in canola crops. The results consistently showed that applying clomazone prior to seeding (pre-plant) canola followed by an in-crop application of a herbicide standard provided acceptable control, usually greater than 85 to 90 per cent. The results also showed the tankmix of quinclorac with a herbicide standard applied in-crop brought control to at least 85 or 90 per cent, without a preseed clomozone application.
In fields where cleavers populations are a big problem, all three products could be used: preseed clomozone, and the in-crop tankmix of quinclorac and herbicide standard. “In the study, using all three products provided the best results, often with an additional five per cent increase over the other combinations,” Willenborg explains. “However, growers have to assess whether or not the use of all three herbicides will pay for itself.” The results of the greenhouse dose-response experiments appeared to suggest cleavers populations responded similarly to glufosinate-ammonium, imazapyr+imazamox, and quinclorac, despite being from different locations in Western Canada. However, further testing and statistical analysis is needed to confirm this.
Both herbicides, although new to Western Canada for cleavers control, are older technologies. Clomozone, which is not yet registered in Western Canada as of December 2015, is a Group 13 product that has been registered in Eastern Canada under the product name Command for several years. Quinclorac, a Group 4 product, is now registered, but growers are cautioned they cannot use quinclorac in canola until the industry addresses MRL (maximum residue limits) considerations in some markets. Registration and acceptance of these herbicides will significantly improve cleavers control in Western Canada.
To manage cleavers in canola, growers should start controlling cleavers in the year before growing canola in rotation, such as in cereals where good control options are available. There are some existing Group 4 products, along with two new products registered in 2015, Pixxaro and Paradigm. The active ingredient in these products, halauxifen-methyl branded as Arylex, also has activity on kochia and can be tank-mixed with a range of other products for control of broadleaf and grassy weeds.
“The most important recommendation is in addition to in-crop herbicide control strategies, the addition of a fall application is key to managing cleavers over the long-term,” Willenborg says. “Growers need to plan to control cleavers that emerge in the fall prior to growing canola. Glyphosate can be used for control, but growers need to recognize the higher risk of developing herbicide resistance in cleavers, and therefore tank-mixes and well-planned herbicide rotations are key. Avoiding tillage is also recommended as tillage can create situations that encourage germination and recruitment of cleavers seedlings.”
Although the addition of these new herbicide options will provide good options for canola growers when available, over the long term they are not a silver bullet. These herbicides, like all herbicide tools, will need to be carefully managed to reduce the risk of herbicide resistance. Cleavers resistance to Group 2 herbicides has already developed across Alberta and Saskatchewan, and cleavers rank second among weeds likely to develop glyphosate resistance in the Black soil zone.
“Our study showed that spring applied clomazone reduced the size and stage of cleavers found in-crop, and it is known that lower population numbers reduce the risk of developing herbicide resistance,” Willenborg adds. “Both clomazone and quinclorac, which can be tank-mixed with any of the in-crop herbicides, also provide alternative modes of action for control and by tank-mixing with herbicide standards, should delay the evolution of resistance to glyphosate and glufosinate.
“However, in the mid 1990s, some cleavers populations in Alberta were identified as resistant to quinclorac, which is Group 4, as well as some Group 2 products, so there are some multiple resistant populations that already exist in Western Canada. Although these resistant populations haven’t spread very much, the scale that quinclorac could be used in canola in the future could mean an increased selection pressure for this herbicide and this could result in the spread of these populations.”
Willenborg is building on this work with some new projects to address some other questions that impact management related to emergence timing and base temperatures. “A better understanding of both emergence timing of spring and fall cleavers, along with corresponding base temperatures, will help us to develop better models to more accurately predict emergence timing for growers,” he says.
“Another area we are looking at is as more growers move to straight cutting and the use of desiccants and harvest aids in harvesting canola, we need to have a better understanding of fall emergence timing of cleavers. Growers need to know what effect a pre-harvest application of desiccants or harvest aids might have on cleavers control and for reducing seed production. Moreover, a significant proportion of cleavers populations emerge in the fall and, therefore, management in the fall is key to the sustainable long-term management of cleavers in Western Canada.”
Apr. 14, 2016 - Lentil acres continue to expand across fields throughout Western Canada thanks to increased prices and demand from export markets. In fact, according to Dr. Bert Vandenberg from the University of Saskatchewan Department of Plant Sciences, Crop Development Centre, "growers in Western Canada now supply half of the world's lentils."
For growers, one of the largest obstacles in meeting this growing demand for the crop is weeds.
"Lentils are poor competitors when it comes to weeds," said Danielle Eastman, Brand Manager, Western Herbicides and Clearfield at BASF Canada. "That is why BASF designed Solo ADV, with reliable control of tough grasses and targeted broadleaf weeds. The new formulation also provides growers with exceptional re-cropping flexibility among the Clearfield system herbicides, particularly for Clearfield lentils.
As lentils are sensitive to many herbicides, Eastman says Solo ADV herbicide provides growers with a safe choice for lentils, with the added benefits of exceptional rotational flexibility in a convenient liquid formulation for easy handling and reduced fill-up times, resulting in time saving and peace of mind.
"We have had good action with our Solo ADV and in a field of small green lentils," said lentil grower Calvin Watson of Avonlea, Saskatchewan. "It was effective on our mustards and other volunteer weeds like canola that we have treated in the past with Solo, but the ease of use was way better. With Solo ADV we are not having to wait for granulars to dissolve and mixing. Just get in the tank and go. The built-in adjuvant eliminates the need to buy, store and add your own at a later time. For us, the benefits of Solo ADV mean less handling of jugs, less chance to spill, along with more time saved."
As lentil acres continue to expand, Eastman encourages growers to maximize the success of their crop with support of the unique benefits of Solo ADV herbicide.
Reducing potential yield losses at harvest, particularly from pre-harvest shattering and pod drop losses, is a priority when harvesting canola. Whether straight combining or swathing, timing of harvest is proving to be one of the most important factors in reducing the risk and magnitude of yield losses.
Researchers at the Indian Head Agricultural Research Foundation (IHARF) in Saskatchewan have wrapped up a four-year study initiated in 2011 to evaluate the relative resistance to pod shatter and pod drop of high-yielding Brassica napus hybrids. The project was conducted at four sites including Indian Head, Melfort, Scott and Swift Current. Researchers evaluated the potential for pod shattering and pod drop of several modern B. napus hybrids across all herbicide systems, including some of the new shatter tolerant varieties.
“With the increasing interest in straight combining, we wanted to evaluate a range of cultivars, including some of the newer shatter tolerant varieties, and identify some that may be particularly well suited for straight-combining,” explains Chris Holzapfel, IHARF research manager. “We compared two harvest dates – one at optimal harvest timing and the final harvest completed three to four weeks later – to see what would happen when harvest was delayed due to weather or other factors. We also wanted to quantify the environmental seed loss contributions from pod drop versus pod shattering under a wide range of environmental conditions.” All canola in the study was straight-combined; however catch trays were used to measure and account for any seed losses that occurred prior to the first harvest date.
“The major finding was that overall timing of harvest was more important than variety,” says Holzapfel. “Regardless of the variety, environmental and crop conditions was the major determinant of yield losses. As well, pod drop versus pod shatter was an important contributor to yield loss.”
The biggest losses on average were from the later harvest date, with pod drop responsible for 43 per cent of the total environmental seed losses with delayed harvest across all hybrids and sites. Losses at delayed harvest ranged from less than five per cent at some sites to more than 50 per cent in one extreme case. At early harvest timing, yield losses from pod drop were typically negligible, averaging 2.5 per cent across all hybrids and sites.
Although the evaluation of various cultivars did show some differences, they were not always consistent from site to site. In an effort to summarize the large data set, all of the hybrids evaluated at any given site were ranked for significant differences compared to the top ranking hybrids for each site (i.e. those with the lowest losses). “The best varieties were ranked a 1, with those showing significantly higher losses ranked a 2 and those with the highest losses receiving a ranking of 3,” Holzapfel explains. “Generally the performance of most of the hybrids was similar under favourable conditions; however substantial losses in all cultivars occurred when severe conditions were encountered. For example, in years where conditions were challenging, such as the severe wind events in 2012 and higher than usual sclerotinia incidence, all of the cultivars were impacted and there were severe losses in all treatments, in some cases more than 50 per cent losses. Hybrids specifically bred for improved shatter tolerance (i.e. L140P and 45H32) were introduced to the study in 2013 and, while overall losses were lower in the latter two years of the study, these hybrids did perform consistently well and can be expected to reduce the risk of yield loss with delayed harvest or severe weather.”
Timing of harvest is important to minimize losses, so in situations where there is quite a bit of variability in the field, growers may want to consider a pre-harvest treatment, although it’s not always necessary. “One of the lessons learned over the years is to be patient, don’t go in too early,” Holzapfel says. “That said, once the canola is ready, harvesting it as soon as possible needs to be a priority to prevent losses. And there is no way around getting into the field and assessing the colour change throughout, not just from the edge of the field. There can also be differences in colour change and varieties from year to year – sometimes the pods will turn but the seeds can still be green; in others there will be seed colour change, but relatively green pods.”
The timing for glyphosate application in Liberty Link canola for straight cutting or swathing is at 50 to 60 per cent colour change. In all systems, the timing of application for desiccant products is at 80 to 90 per cent colour change. Holzapfel adds when there is quite a variation in canola staging, like we are seeing in 2015, assessing harvest timing gets more difficult and can be tricky. “Thin stands may be well suited to straight cutting, and although there may be some losses, there will also be losses from swathing, so there is no easy solution.”
Both systems, whether swathing or straight-combining, have risks, with timing of harvest the most important management factor. Recent research at the University of Saskatchewan on commercial farms showed that total seed losses (environmental + header + threshing) for swathed and straight-combined canola were equal and ~10 per cent on average. “Swathing too early results in significant yield loss due to smaller seeds and can lead to higher green seed counts,” Holzapfel explains. “Swathing too late results in yield loss due to pod shatter. Similar to straight-combining, the risk of environmental and header losses increase over time as canola swaths remain in the field, but for straight-cutting, harvest timing is usually more critical than with swathing. Therefore, growers should limit straight-cut acres to what is easily manageable to gain experience and confidence in the practice.”
Overall, the project results indicate all hybrids evaluated could be straight-combined successfully provided that harvest was completed in a reasonably timely manner. Other factors such as overall yield potential, days to maturity, standability and herbicide system are still the most important factors to consider when choosing a canola hybrid with the intention of straight-combining. Hybrids with improved pod shatter tolerance lengthen the window for straight-combining and reduce the overall risk of yield loss.
There are new shatter tolerant varieties coming on the market for 2016, and Holzapfel expects that more varieties will continue to be released in the future.
“We know that most existing equipment will work adequately, including draper, rigid and flex headers,” Holzapfel says. “Header extensions significantly reduce header losses and are a good option for straight-combining large acres of canola, and headers with variable knife position should provide similar benefits. We are collaborating on another three-year project led by Nathan Gregg of PAMI that started in 2014 to evaluate the performance of commercial straight-cut headers for canola using full-scale machinery and large plots at Swift Current, Indian Head and Watrous. Harvest treatments will be evaluated on two varieties, a standard canola variety InVigor L130 and a shatter resistant variety InVigor L140P.” The final report and results will be available in 2016.
Sept. 1, 2015, Mississauga, ON - According to a recent poll conducted by FarmShift on behalf of BASF Canada, the number of growers straight cutting canola in Western Canada rose by 50 percent from 2013 to the 2014 harvest season.
The poll included a sample of 400 growers from across Western Canada with minimum canola acre thresholds.
"We know that straight cutting is a practice that is becoming more and more common," said Danielle Eastman, Western Herbicide Brand Manager at BASF Canada. "Growers who straight cut save time, labour and cost at harvest time."
The practice of straight cutting canola is gaining popularity. In fact, according to the study 65 percent of growers surveyed are interested in straight cutting and 82 percent of the growers who have already adopted the practice plan to do more of it.
"BASF is committed to providing growers with the tools that will help them produce the best possible crop," said Eastman. "Tank-mixing HEAT® LQ with glyphosate helps growers get into the field sooner and harvest a more even crop, which helps contribute to a successful straight cut harvest."
Using a desiccant at harvest time not only gives growers the ability to get in the field and harvest sooner, but also helps prepare for the following season by controlling winter annual and perennial weeds.
For more information about HEAT LQ, contact AgSolutions® Customer Care at 1-877-371-BASF (2273).
Aug. 24, 2015 - The environmental conditions in 2015 have resulted in many fields having two or more growth stages present. Proper management of these fields will help ensure an efficient harvest.
"Many areas of the province have been subject to adverse growing conditions in 2015," says Mark Cutts, crop specialist with Alberta Agriculture and Forestry, Ag-Info Centre, Stettler. "Crops were subject to many stresses including poor soil moisture conditions, cool soil temperatures and frost. As a result of these adverse conditions, many crops have at least two crop stages present. Fields with variable growth stages will have areas with mature plants, while other areas of the field will be immature. Having variable growth stages complicates decisions regarding timing of harvest operations."
As harvest approaches, Cutts says producers will need to consider their options for managing these fields.
"The main management options available for dealing with variable stage crops include swathing the crop or using herbicides (e.g. glyphosate or a crop desiccant). Regardless of the approach used it should be recognized that managing variable growth stages typically requires the growth of the less mature portions of the field to be terminated. As a result, these areas of the field will not contribute to yield. The advantage of these approaches is the elimination of the variable crop stages and improved harvest management."
One approach that producers could use is the application of glyphosate to a standing crop. Applying glyphosate to a standing crop is commonly referred to as a "pre-harvest application" and is primarily done to control perennial weeds. Glyphosate is a systemic herbicide that moves through the foliage into the plants root system and results in death of the plant. As a result of its behaviour in the plant, glyphosate applied to a standing crop will terminate the growth of the crop and over a period of time the entire field will dry down.
Another chemical option for producers is the use of a desiccant. Desiccants are a non-selective contact herbicide that act rapidly and result in the termination of the above ground growth of crops and weeds. This allows for a quick dry down of the plant material and an earlier harvest. Desiccants are most commonly used on potatoes and pulse crops. However, desiccants do not provide long-term weed control.
"Swathing the crop can also be an effective management tool for crops with variable growth stages," says Cutts. "For example, if a cereal crop has late developing tillers the crop should be swathed when the original heads are at the correct stage (kernel moisture of 35 per cent or less) and before there is any amount of kernel development in the late tillers. This approach will minimize the risk of having green immature kernels that may impact grain grade."
Canada has seen tremendous growth in lentil production as lentil consumption has soared over the last few years. According to Bert Vandenberg, University of Saskatchewan Plant Sciences Department, Crop Development Centre, world lentil consumption has gone up four to five times relative to the human population. Lentil production in Saskatchewan alone has gone from 25,000 acres in 1983 to more than three million acres today. With growth like this, it is no wonder the future looks so promising.
"The future of lentils is very bright," said Vandenberg. "Here in Canada, we have developed the technologies for successful crop production and the truth is, people like to eat lentils. I predict that next year Canada will grow 50 per cent of the world's lentils. That will be 80 per cent of the world's exports."
The fundamental principle contributing to the future of lentils is education in crop rotation and the benefits of sticking with it. Crop rotation extends the life of all the tools on the farm, including disease control, weed control and overall productivity. In the lentil crop, herbicide resistance is a concern because it is a less competitive crop.
"My number one piece of advice is stick with a crop rotation that is appropriate because otherwise you risk losing your weed control," said Vandenberg. "You risk shifting weed populations and probably lowering your productivity when you shorten the rotation. Crop rotation is a long-term enterprise."
Looking at the history of Western Canada, weeds have always been the number one issue that limits productivity in lentils. Herbicide tolerance is a useful tool for farmers combating resistance issues.
"Herbicide tolerance in lentils gives you a really good option for weed control," said Vandenberg. "Weed control is the number one thing that you need to grow a lentil crop successfully. I'm thinking that 80 to 90 per cent of lentil production is now with herbicide tolerance for Group 2 herbicides, also known as Clearfield lentils."
BASF is invested in research and the future of lentils, and will continue to invest a portion of Clearfield lentil herbicide sales back into the Crop Development Centre (CDC), when matched with a signed commitment. BASF is working with growers to provide the best possible cropping system that will enhance the future of Canadian agriculture.
Since the widespread adoption of both Roundup Ready (RR) corn and RR canola, growers have been struggling with controlling volunteers. Until 2015, controlling RR volunteer canola in RR corn was possible, but with some potential crop tolerance issues. From 2011 to 2013, Wilt Billing, agronomist with DuPont Pioneer, looked at some commonly used herbicides in corn that specifically targeted glyphosate-resistant volunteer canola.
“The herbicides were all being used by commercial growers and the products all had potential harmful implications,” Billing notes. He has a special interest in weed control as DuPont Pioneer sells RR corn and Billing wanted to help growers get the most out of their corn genetics.
Billing looked at five different herbicide treatments on four industry-leading Pioneer and other brands of RR corn hybrids. Glyphosate alone was used as a check to assess herbicide tolerance and weed control.
Herbicides were applied at the V3 stage of corn growth (see Table 1). Treatments were replicated four times over three years. Herbicide injury scores were recorded at three to five, seven to 10, and 21 to 24 days after post-emergent herbicide application. Brittle snap, test weight, yield and per cent moisture content were also observed. In the glyphosate-only treatment, after herbicide application any volunteer canola plants were removed in order to have a valid yield and test weight comparison.
Dicamba, 2,4-D and MCPA amine are Group 4 herbicides that work to produce abnormal growth in weeds. Bromoxynil is a Group 6 contact herbicide. All herbicides are registered on corn.
“I wanted to see if the Group 4 herbicides were impacting corn growth and compare that to bromoxynil,” Billing says. “Over the three years, we saw some consistent trends.”
Severe and persistent herbicide injury resulted from 2,4-D on all hybrids. 2,4-D showed the highest brittle snap in all hybrids (see Table 2). On average 2,4-D reduced yield by 13.5 per cent and lowered test weight by 4.4 lbs/bu.
Billing explains that MCPA amine increased brittle snap counts and displayed significant onion-leafing symptoms. Dicamba produced stalk lodging and increased brittle snap counts with significantly reduced yield and test weights. 2,4-D, MCPA and dicamba produced stunted plants and poor brace root development when compared to bromoxynil and the glyphosate only check. Bromoxynil caused minor leaf scorching, but produced no growth inhibition or brittle snap and plants recovered quickly.
“All the bromoxynil treatments looked fairly good. It wasn’t inhibiting growth of the corn crop. There was some flash burn, but within two to three days after application, the corn outgrew the minor injury and was healthy. With Group 4 products, it set the corn back seven to 12 days. There was often a staging difference at maturity,” Billing says.
Overall, Billing says bromoxynil treatments had the highest yield, lowest crop injury, no crop stunting, no brittle snap and no reduction in test weight. (See Fig. 1.)
When applying bromoxynil to corn, Billing recommends application during warm temperatures but not at temperatures greater than 27 C. High water volumes of at least 10 to 15 gallons per acre are recommended to reduce crop stress, and applications should be avoided during or immediately following environmental stress on the corn crop.
New registration makes control easier
Since Billing conducted his research, a new active ingredient has been registered in Western Canada for use on field and sweet corn to provide better grassy and broadleaf weed control. The active ingredient is topramezone – a Group 27 herbicide – sold by BASF as Armezon and by UAP as Impact. Volunteer canola is not yet on the label, but control at the one- to six-leaf stage has been submitted for addition to the label.
“I’ve looked at Armezon and Impact in demonstrations on commercial fields and I think these herbicides will become leading products for use on corn crops in Western Canada,” Billing notes. “[They do] a very good job on broadleafs and I haven’t seen any crop injury. It looks very safe on the crop.”
Tropramezone should be tank-mixed with glyphosate for application to RR corn and can be applied from the one- to seven-leaf stage. The tropramezone and glyphosate tank-mix provides control of all weeds on the glyphosate label, plus it provides improved control of barnyard grass, green and yellow foxtail, chickweed, lamb’s quarters, ragweed, smartweed, redroot pigweed and wild mustard.
DuPont Pioneer is also looking at some of the chemistries registered on corn just south of the border in North Dakota, and the company hopes to be able to work with other pesticide companies to support registration efforts in Western Canada.
Volunteer canola is becoming a bigger weed management challenge for canola growers, particularly where high frequency rotations are in place. Recent weed surveys in Saskatchewan show volunteer canola has moved up on the list of most common weeds, from the low 30s in the 1980s to number 14 and higher today.
“Volunteer canola can be problematic for canola growers even though we don’t always think of it as a true weed,” Christian Willenborg, assistant professor with the department of plant sciences at the University of Saskatchewan says. “Volunteer canola creates a lot of risk and negative issues, even in a canola crop itself.”
As a weed, volunteer canola competes with the crop for nutrients and can make those nutrients unavailable to the crop. Typically, volunteers don’t make a positive contribution to yield because they reduce crop yield and don’t return the same yield relative to the crop. As well, because volunteer canola is the result of a different hybrid generation, there can be hybrid breakdown and loss of positive traits.
During the cropping season, volunteer canola creates other management challenges. Because volunteer canola is not treated, it presents the risks of developing seedling disease and increased flea beetle pressure. In non-canola years, volunteer canola can serve as a host for serious diseases such as blackleg and clubroot, reducing the effectiveness of rotation in managing those diseases. Volunteer canola often flowers and matures at different times than the crop, making harvest timing and management more difficult, particularly for growers looking at straight cutting. Early maturing volunteers can also return seed back to the seedbank, which continues to increase the problem of volunteers.
“One of the best ways to manage volunteer canola is to lengthen the crop rotation,” Willenborg explains. “There is evidence from some of our studies at the university suggesting volunteer canola is a major problem of tight canola rotations. Extending that canola rotation beyond continuous canola or every second year to a minimum of three years is recommended. A four-year rotation is even better, with the three years intervening the canola crop providing better opportunities to manage volunteer canola and other weed and disease concerns.”
Willenborg points to research work conducted by Rob Gulden, now at the University of Manitoba, that looked at the persistence and issues of secondary dormancy of volunteer canola seeds. “His work showed that 44 per cent of canola seeds disseminated or replenished in the seedbank will persist for one winter, 1.4 per cent for two winters and less than 0.5 percent for three winters. Therefore, a three- or four-year rotation will help growers minimize the seedbank inputs and diminish the volunteer canola population over time,” he says.
Reducing harvest losses is critical to minimizing seedbank inputs. Generally, harvest losses for canola can average one-half bushel per acre, which is actually five times the seeding rate. Therefore, trying to minimize harvest losses as much as possible is critical to reduce seed return to the seedbank. Also, avoiding tillage in the spring to allow for maximum volunteer canola emergence is important. Tillage can actually put the volunteer seeds in favourable microsites for germination as well as induce seed dormancy.
For controlling volunteer canola, both a preseed and in-crop treatment will be a critical strategy for control. The type of control may differ year-to-year depending on rainfall and other factors. “Volunteer canola control can require a herbicide with some residual control, or multiple herbicide applications with products that lack residual control, as there can often be multiple flushes during the growing season,” Willenborg explains. “Therefore, a pre-emergent application may miss some of the later emerging weeds, but if you wait for in-crop control, some of the early emerging volunteers may be too large by the time the post-emergent application is made. Think about volunteer canola when you are selecting products for the other weeds in your field.”
One of the best strategies for managing volunteer canola prior to a canola crop is to plant a cereal crop. Cereals provide a broad range of herbicide options, both preseed and in-crop, that can provide good control. Willenborg explains should stacked volunteers (tolerant to more than one herbicide) become a problem, growers can still get very good control with products registered in cereals. “Using 2,4-D or MCPA, or using any of the various products available that can be tank-mixed with glyphosate preseed before wheat or barley, often provide control. Pre-emergent glyphosate with a tank-mix partner is key to managing volunteer canola in combination with whatever herbicide resistance system a grower is using,” he says.
Because volunteer canola can create a green bridge for diseases and other pests, growers need to minimize weed seed return of volunteers and try to eliminate volunteers from those crop rotations. “For a disease like clubroot where the incidence is increasing, volunteer canola can serve to perpetuate that problem,” Willenborg says. “Therefore, it is absolutely critical that growers with clubroot problems or other serious disease issues control those volunteers and really employ, if they can, a zero threshold strategy for volunteer canola. Certainly the tighter the canola rotation, the more difficult eradication or minimizing seed set from those volunteers is going to be.”
Another strategy to control volunteer canola includes diligent field scouting. Scouting rotational fields, and even those ahead of canola for volunteer canola not controlled by herbicide application, is important. “Early detection allows time for control of those volunteers before seed set,” Willenborg says. “Leaving canola seeds on the soil surface after harvest and delaying any tillage operations for a few weeks gives seeds time to germinate in the fall. Seedlings emerging in the fall are unlikely to survive the winter. In addition, during that time, birds and insects, especially carabid beetles, will actually consume a lot of those seeds.”
Good rotations of both crops and herbicides are needed, not just for weed management overall, but also for control of volunteer canola. “Extending the crop rotation, growing canola less frequently and using integrated weed management strategies helps to reduce volunteer canola and the associated production risks,” Willenborg adds. “Rotation among herbicide-tolerant systems and use of preseed herbicide timing in addition to in-crop application helps improve weed management and reduce the risk of developing herbicide-resistant weeds. Growers should try to start with a clean field and stay with a clean field by controlling weeds extremely early and right through the growing season.”
A problem perennial weed in many cropping systems, Canada thistle, has consistently ranked in the top five weeds in the Canadian Prairies in relative abundance. To optimize perennial broadleaf weed control, herbicide selection and use must be co-ordinated with crop rotations and cropping practices over the long term.
Researchers with Agriculture and Agri-Food Canada (AAFC) at Indian Head, Sask. and the University of Saskatchewan conducted a four-year project to study the effect of herbicide timing and intensity on the control of Canada thistle in a cereal-oilseed-cereal-pulse rotation under a no-till management system. Trials were set up at Indian Head and Saskatoon from 2004 to 2008. The previous cropping system was low-input minimum tillage at all sites. The Canada thistle densities at Indian Head were 40 to 50 Canada thistle plants per square metre in an existing field, and densities at the other sites were slightly lower.
“The study was set up with six treatment combinations varying in intensity and timing of Canada thistle control with clopyralid being applied in-crop, and glyphosate being applied pre-harvest, post-harvest or in-crop,” AAFC crop management agronomist Bill May says. The six treatment combinations were check (no perennial weed control), clopyralid high intensity, glyphosate high intensity, clopyralid + glyphosate high intensity, clopyralid + glyphosate medium intensity and glyphosate medium intensity. A preseed glyphosate application was included in all treatments.
The treatments were applied to a wheat-canola-barley-pea rotation with all four phases of the rotation grown each year. For the cereal crops in rotation, an in-crop application of Buctril M was used for the check and glyphosate medium and high intensity treatments, while Curtain M was used in cereals for the clopyralid high intensity and the two clopyralid combinations with glyphosate. An in-crop application of Odyssey was applied to the pea crop in rotation. Roundup Ready canola received an in-crop application of glyphosate with all of the treatments, except the glyphosate high intensity treatment that included two in-crop glyphosate applications, and the clopyralid high intensity treatment that included an in-crop application of Eclipse.
The study results showed differences between the treatments in their control of Canada thistle and subsequent effect on grain yield. “Overall, the five treatments with some Canada thistle control increased the visual control of Canada thistle and reduced the density of Canada thistle compared to the check,” May explains. “Two treatment combinations, the glyphosate high intensity (pre- or post-harvest) alone or in combination with clopyralid (in-crop) were the most effective in reducing Canada thistle density and increased visual control of Canada thistle more than the other three treatment combinations. These two treatment combinations also had a higher yield in all four crops compared to the check. In addition, the clopyralid high intensity treatment combination increased grain yield compared to the check in three out of four crops.”
In the study, all four crops were grown in rotation every year. However, the results showed there was little difference in which crop was the first one in rotation. Averaged over the four years of the study, there was little difference in grain yield, Canada thistle control or Canada thistle density in any of the crop rotation combinations. This indicates that control of Canada thistle can be successfully initiated when any of these crops are grown.
“We used good agronomic practices in all of the treatments in the study, as well as the herbicide treatments,” May says. “Using proper fertilizer rates, earlier seeding dates, good timing of annual weed control applications and good harvest management actually started to lower the counts of Canada thistle every year as we went along, even in the check treatment. Good management practices definitely helped us manage the Canada thistle, although it didn’t mean an automatic yield increase.”
May adds there can be an allelopathic effect of Canada thistle in the crop, so high density of the weed one year can affect a crop’s yield the next year. “As soon as you let off the control of Canada thistle or control was weak, then the Canada thistle started bouncing back fairly quickly,” he notes. “That’s the problem with trying to manage thistle every second or third year in rotation. If you don’t manage it consistently, then the populations sneak back up and take over. The plant can grow back from its extensive root system if it hasn’t been killed completely. Therefore, it takes at least two or three years of a concerted effort to get Canada thistle controlled. Even after four years, Canada thistle populations can start to rebound if control measures stop.”
The results from this study indicate that combinations of in-crop and post-harvest applications of herbicides can be effectively used to control Canada thistle. The control can be successfully initiated in most crops in a rotation sequence, even when a weakly competitive crop like peas are being grown. A consistent approach over several years is required to gain effective control of Canada thistle.
Easy to grow. Easy to harvest. Nitrogen-fixing pulse crop. What’s not to like about growing fababeans? That’s why farmers on the Prairies are catching on.
“There was a big acreage increase in 2014,” says Mark Olson, unit head, pulse crops with Alberta Agriculture and Rural Development (AARD) at Stony Plain, Alta. “Some of the acreage could be from guys who have never grown pulses because they had heard about the lodging challenges with field pea and they may have had rocky land not suited to peas. But with fababeans, they pod fairly high off the ground and don’t lodge, so it is opening up more acres to pulses.”
In 2014, crop estimates put the acreage on the Prairies at approximately 100,000 acres, with the bulk in Alberta at almost 80,000 acres, followed by Saskatchewan with 18,000 acres and Manitoba with about 3500 acres. Olson thinks the potential could be in the 400,000 to 500,000 acre range.
The increase in fababean production is in part fuelled by improved varieties that mature early and yield well, along with the development of low tannin varieties. Tannins are not suitable for non-ruminant animals such as pigs, horses, rabbits, cats and dogs. Cattle can digest tannin-type fababeans, and they are also popular in the human edible market in the Middle East and Asia.
Markets are being developed on the Prairies. Locally, fababean producers can look to companies like AGT Food and Ingredients, Parkland Alberta Commodities, and feed companies to contract and sell fababeans. Prices have come down from their highs of a few years ago, and are ranging in the $6 to $7 per bushel range. Yield potential is high, with dryland yields in the 70 to 80-plus bushels per acre and irrigation yields in the 125-plus bushel range.
Olson’s pulse unit has been involved in fababean research for several years. With small plot research providing valuable information on agronomics and farmer experience expanding the knowledge base, fababean production is becoming more dependable with less risk.
Fababean variety selection should be based on a combination of tannin type and agronomic performance. FB 18-20 and Malik (9-4) have white flowers with a black dot and tannin-containing seed coats (seed coats are brown). These cultivars were bred by Dr. Bert Vandenberg at the Crop Diversification Centre in Saskatoon, Sask., and are available for contract production.
Imposa and Snowbird have white flowers and seed coats that have very low levels of tannins (seed coats are white). These cultivars were bred in Lelystad, Netherlands. Two new zero-tannin varieties, Snowdrop from CDC and Tabasco from NPZ Lembke (DL seeds), are in market development, and a few more are in the development pipeline.
Fababean is a cool season crop that likes good soil moisture and cool temperatures. Olson says hot temperatures can cause flower blast similar to what happens to canola if a heat wave occurs during flowering. Fababean requires a longer growing season, and early seeding is particularly important for high yield and good seed quality. Late seeding will result in frost-damaged seed, which limits the marketing of the product.
Research in north central Alberta emphasizes the importance of early seeding. Seeding as early as possible produced yields of 94 bushels per acre, while seeding two weeks later resulted in a 32 per cent loss in yield, dropping to 71 bushels per acre.
“That is a pretty significant loss in yield,” says Olson. “Our recommendation is to seed as early as you can get onto the land (have traffic ability), and try to seed by the end of the first week of May. Fababeans have good spring frost tolerance, and if frozen off the plants, will regenerate from nodes at or near the soil surface.”
High seeding rate is also important. Research conducted by research scientist Sheri Strydhorst with AARD found that increasing seeding rates can reduce time to maturity and increase yield. The current recommended seeding rate is 43 plants per square metre (four plants per square foot), but her research found that increasing seeding rate to 65 plants per square metre contributes to higher yields, especially under dry growing conditions. (See Figure 1.)
Additionally, higher seeding rates also hastened maturity when the crop was seeded late (May 27); however, late seeding is not recommended. The research found that increasing the seeding rate from 32 plants per square metre to 65 plants per square metre increased the percentage of black pods from 65 to 75 per cent by the second week of September. The researchers stated that ideally, fababeans should have 90 per cent black pods by the second week of September, which can usually be achieved with early seeding. In years when late seeding occurs, higher seeding rates can help enhance maturity, but this approach is still not as effective as early seeding.
Olson cautions that seeding rate should be based on thousand seed weight since there is a large variation in seed size between fababean varieties. Varieties range from 350g to 750g per 1000 seeds, which is huge. To hit the targeted plant population, the seeding rate could vary from four to 5.5 bushels per acre. With a seed size that ranges from 30 per cent to 100 per cent larger than field pea, Olson says some air delivery systems could be challenged by the volume of seeding moving through the manifolds, especially if growers are pushing seeding rates up to 65 plants per square metre. As well, it is critical growers check to see if the fababean seed can flow through the end of the seed boot.
Fababean seed should be inoculated with a nitrogen-fixing rhizobia bacteria. Olson says fababean is the highest nitrogen-fixing pulse crop, and the inoculant should be specific to fababean so that nitrogen fixation occurs late into the growing season. Monsanto BioAg (formerly Novozymes) recently received registration for granular TagTeam, and Becker Underwood Canada has a self-adhering peat-based inoculant registered for fababean called Nodulator.
Fababeans use relatively high amounts of phosphorus (P), but are relatively sensitive to P fertilizer placed in the seed row. A maximum of 20 pounds per acre P2O5 is recommended in the seed row. Higher rates should be banded. In research trails, two sites showed a response to 20 pounds of P2O5. Meanwhile, sulphur should be applied based on soil test recommendations.
For growers worried about seed rot, seedling blight and root rot caused by Fusarium spp., Rhizoctonia solani, and Pythium spp., Olson says fababean appears to be more resistant than pea, but time will tell. He notes farmers have observed that when fababean is substituted for pea in a four-year rotation, the incident of root rot is decreased. Olson says early indications are that fababean may also have good resistance to Aphanomyces euteiches, a new strain of root rot of field pea that is causing concern in Western Canada.
“Stay tuned on this one. Early indications are our current fababean varieties have good resistance. France was ground zero for Aphanomyces, which a had dramatic effect on the pea industry there,” says Olson, who adds we can learn a lot from the French researcher’s experience and knowledge.
Growers should also pay careful attention to herbicide residues from previous years when selecting fields for fababean production. Fababean is quite sensitive to some herbicides, and growers should review herbicide labels to determine if there is a potential for seedling injury.
Another interesting research study conducted in 2004 found that honeybee pollinators had a positive impact on fababean yield. Medhat Nasr, AARD provincial apiculturist, found that honeybees in caged fababean plots increased yield by 26 per cent compared to open plots. Yield of fababean plots five metres away from honeybee hives increased by 47 per cent, and plots 250 metres from beehives increased 29 per cent compared to plots 500 metres away.
Protecting the crop
Olson says fababean has similar weed competitiveness as field pea. He says targeting a plant stand of at least 45 plants per square metre will help the crop compete with weeds.
While registered herbicides are limited, there are some choices. Basagran, Odyssey, Edge Granular, metribuzin (Sencor) + Treflan (trifluralin) in a pre-plant incorporated mix, Poast Ultra, Assure II and trifluralin alone can be used to control weeds. Authority, a preplant or pre-emergence herbicide for control of broadleaf weeds, was recently registered. Viper ADV has been forwarded for minor use registration.
“Don’t use MCPA or Sencor [metribuzin] as post-emergent herbicides. They are pretty tough on fababean and for that reason minor use registration was not pursued,” says Olson.
From an insect perspective, Olson says pea leaf weevil seems to prefer fababean over pea, and bertha armyworm and lygus bug can also be pests. In Saskatchewan and eastern Alberta, the blister beetle has been seen attacking fababean. Grasshoppers can also be a major insect pest. Lambda-cyhalothrin (Matador) is registered for use of control of insects on fababean. Consult labels for registered insecticides and preharvest intervals.
Chocolate spot caused by Botrytis fabae and Botrytis cinerea has been observed on some fababean crops, but Olson says research needs to be done to figure out whether it is economical to spray. There are no registered fungicides for control, although Lance fungicide is registered for sclerotinia control on fababean and it is also registered for control of botrytis in pea, lentil and chickpea. Following a four-year rotation is the best strategy for managing disease in fababean.
Fababeans are suited to straight cutting with good standability and pods quite high off the ground. As the crop matures, the lower leaves darken and drop, and the bottom pods turn black and dry from the bottom to the top of the plant. To reduce shattering, Reglone desiccant can be applied when most plants are ripe and dry, when pods are fully filled and when bottom pods are black in colour. Combine when moisture content of the seed is at 18 to 20 per cent, and aerate to 16 per cent for safe storage.
Where fababean acreage ends up in 2015 will depend on a combination of seed availability, market opportunities and commodity prices relative to other crops. What is certain, though, is that fababean still has much upside potential.
The cleavers weed challenge continues to be a particularly sticky issue on soils with greater than six per cent organic matter. Cleavers are widespread in the Black soil zone, and a growing Group 2 resistance problem is particularly challenging for pea growers.
Traditionally, cleavers were easily controlled in peas with Pursuit (imazethapyr, Group 2) or Odyssey (imazamox + imazethapyr, both Group 2). However, these old standbys are becoming less useful, as the incidence of Group 2 resistant cleavers grows. In addition, past weed surveys show that cleavers are increasing in abundance at the fastest rate of all weeds, further compounding the problem.
“Pursuit and Odyssey provided pretty good control in peas, but when you look at the options left for growers in the Black soil zone with organic matter greater than six per cent, there are only a couple of herbicides registered that will provide suppression of Group 2 resistant cleavers,” says Ken Sapsford, research assistant at the University of Saskatchewan.
The herbicides Basagran (bentazon, Group 6), Edge (ethafluralin, Group 3) and Viper (imazamox + bentazon, Group 2 + 6) are registered for suppression of cleavers on soils with organic matter (OM) greater than six per cent. Suppression is rated as weed control between 70 and 80 per cent. To be registered for commercially acceptable control, a herbicide must provide greater than 80 per cent control.
With support from the Saskatchewan Pulse Growers, Agriculture and Agri-Food Canada and FMC Canada, Sapsford investigated additional options for cleaver control on high OM soils. He looked at three herbicides that had potential for cleaver control: Authority, Heat and Command. Recognizing that none of the existing or potential herbicides could provide commercial control on their own, he assessed sequential applications of the three potential herbicides with the three existing herbicides registered for suppression: Basagran, Edge and Viper.
Authority herbicide (sulfentrazone, Group 14) is registered on field pea for suppression of cleavers on soils with less than six per cent OM. However, it does not provide suppression on soils greater than six per cent OM.
Heat herbicide (saflufenacil, Group 14) is registered on field pea, and will control cleavers that are present at time of application, but is not registered for residual control in crop.
Command herbicide (clomazone, Group 13) has some activity on cleavers when used preplant and may be safe on pea. However, Command is not registered for cleaver control, and is only registered in Eastern Canada for use on sweet potatoes, soybeans and cucurbits.
Sapsford explains that residual activity is an important feature for cleaver control since cleavers grow as both a winter and spring annual, and also has several flushes throughout the spring. A preseed burndown of winter annuals is important, but ideally, the products should have residual control to control multiple flushes throughout the spring.
“For control of cleavers in the Black soil zone, you want residual control,” says Sapsford.
Research plots were established at Melfort, Sask., on a Black loam soil with 6.4 per cent organic matter and a 6.5 pH, and at Rosthern on a Black loam soil with 6.5 per cent organic matter and a pH of 7.5.
Sapsford first assessed cleaver control of Authority, Heat and Command individually. Authority achieved suppression of cleavers at twice the registered maximum rate, but with variability ranging from 50 to 100 per cent.
Command applied pre-emerge at the low, medium or high rate provided very little control of cleavers. While the cleavers showed signs of injury early in the growing season, with reduced growth and a whitened appearance, by the July assessment timing, Sapsford says there was “virtually no control of cleavers, and the cleavers were re-growing.”
Heat alone applied pre-emerge provided poor long-season cleaver control. “By itself, Heat didn’t do much for residual control of cleavers…it will burn off the ones that are there and they are controlled. But when several more flushes came, Heat provided some short-term residual control but didn’t provide long-term residual control,” explains Sapsford.
Authority herbicide applied pre-emerge provided some residual control of cleavers but still not enough to be rated as suppression when applied alone.
Of the registered herbicides, Edge provided control of cleavers early in the growing season, but Sapsford says end-of-season ratings in July found only 60 per cent control. Viper provided suppression of cleavers, as supported by the label.
Sapsford trialled two rates of Basagran. The regular registered rate, and the rate of Basagran that is included in Viper herbicide, which is roughly 40 per cent of the full Basagran rate. Both rates of Basagran provided suppression of cleavers. The cut rate of Basagran was included so that Sapsford could assess whether Viper was controlling both Group 2-resistant and no-resistant cleaver biotypes. He realized pea growers would most likely use Viper rather than Basagran, because Viper has a wider range of weed control.
Where things started to get interesting is when Sapsford started to experiment with sequential applications of two herbicides. He found the combination of pre- and post-emergent herbicides quite often provided control upwards of 100 per cent when rated at mid to late July. The combination of residual and contact herbicides helped to control the cleavers throughout the season, which helped to reduce seed set. By using a combination of multiple groups of herbicides, Sapsford says pea growers can also help prevent and manage Group 2 herbicide resistant cleavers in the Black soil zone.
“Most burnoff applications will also include a glyphosate (Group 9) application, so a pea field would be receiving at least three modes of action. That can help manage or delay Group 2 cleaver resistance,” he says.
Sapsford had success with the following sequential herbicide applications for Group 2 resistant cleavers on soils with greater than six per cent OM (see Table 1):
- Fall Edge followed by spring pre-emerge Authority
- Fall Edge followed by spring post-emerge Viper
- Spring preseed Heat followed by post-emerge Viper
- Spring pre-emerge Authority followed by post-emerge Viper
- Spring pre-emerge Command followed by post-emerge Viper
The most effective sequential applications among the registered pea herbicides were Edge followed by Authority or Viper, Heat followed by Viper, and the high registered rate of Authority followed by Viper.
The unregistered Command herbicide followed by Viper also provided a high degree of control.
The different herbicide options provide growers with choices to fit their farming and crop rotational practices. Edge would fit for growers who utilize tillage in their farming practices. Heat, Authority and Viper fit with reduced and no-till applications.
“Growers are starting to look at fall-applied Edge with heavy harrow incorporation. That’s not on the label, but if they have time in the fall, some are starting to try Edge because of resistance management problems,” says Sapsford.
Heat, Authority and Viper, though, have recropping restrictions, which growers must consider. The major crops, including wheat, barley, oats and canola, can be grown the year after Heat and Viper applications. Authority has a recropping interval of 12 months for canola and 24 months for lentils. In the Black soil zone, this should not cause a problem, as wheat typically follows pea crops in rotation, and lentils aren’t grown in the Black soils.
“The one application that fits into many cropping plans is a spring application of Authority with glyphosate followed up with
Viper in-crop. It was providing excellent control, and with Viper controlling both grassy and broadleaf weeds, it picks up what Authority misses in the preseed application,” says Sapsford.
Viper following Heat also provided better than 90 per cent control. Sapsford says the research may help growers in the Black soil zone move pea cropping back into the rotation.
November 7, 2014 - Ontario has several weed species with herbicide resistance, but the ones with glyphosate resistance (GR) are a special challenge because of glyphosate’s pivotal role in the production systems on many farms. As well, some GR weeds have developed resistance to other herbicides, making the control challenge even tougher. For farmers, managing GR weeds could mean higher weed control costs and, in some cases, a loss of effective herbicide options in specific crops. So, Ontario researchers are evaluating the latest herbicide options as well as non-herbicide alternatives for managing GR weeds.
A quick look at the issue
Currently in Ontario, three weed species have been confirmed as having GR populations – biotypes that can survive and reproduce after exposure to what used to be a lethal dose of this herbicide. They are giant ragweed Ambrosia trifida, Canada fleabane Conyza Canadensis and common ragweed Ambrosia artemisiifolia.
Dr. Peter Sikkema of the University of Guelph-Ridgetown leads an annual survey of GR weeds in Ontario. The survey shows GR weeds are an increasing problem. GR giant ragweed biotypes were first confirmed in 2008 and have now been found in seven counties. GR Canada fleabane, first found in 2010, is now in 12 counties. And GR common ragweed biotypes were first confirmed in Essex County in 2011, but so far none have been found beyond that county. Some GR biotypes of these three weeds are also resistant to FirstRate, a Group 2 herbicide.
Herbicides are grouped are based on their mode of action – the way their active ingredients attack the plant. For example, Group 2 herbicides block the normal function of an enzyme referred to as ALS/AHAS. Group 2 includes a large number of active ingredients in several chemical families, such as the imidazolinones and sulfonylureas. Group 9 includes only one active ingredient – glyphosate. It inhibits the EPSPS enzyme.
When you apply a herbicide to control a weed species, you select for the few individual plants within the population that happen to be able to resist the herbicide’s mode of action. If that resistance is heritable, then those surviving plants can produce offspring with that resistance. If you use herbicides with the same mode of action year after year, then eventually the only weeds remaining in the field will be those that are resistant to that mode of action.
Sikkema’s surveys show the scope of Ontario’s GR weed problem, but they don’t necessarily catch every single GR weed in the province. So it’s very important for growers to scout for possible herbicide-resistant weeds in their fields so they can deal with the problem before it explodes. At the University of Guelph, Dr. François Tardif’s lab does testing to determine if suspect weed samples are indeed herbicide-resistant.
Assessing herbicide options
Sikkema’s research group is evaluating a wide range of herbicide options for each of the three GR weeds, with funding from Grain Farmers of Ontario, CanAdvance, and the herbicide manufacturers.
Sikkema outlines some highlights from his group’s recent studies in corn, soybeans and winter wheat.
For GR giant ragweed control in corn, they are testing preplant and post-emergence herbicide options in tank mixes with Roundup. “In the preplant programs in corn, the most effective treatments are Marksman and Callisto + atrazine,” he says.
“Similarly, for post-emergence herbicides in corn, the ones that contain dicamba have been most effective: Banvel, Distinct and Marksman. Pardner + atrazine has looked interesting as well.”
In winter wheat, most of the herbicides they’ve tested have given good control of GR giant ragweed, including 2,4-D ester, Target, Estaprop, Lontrel and Trophy.
For GR giant ragweed control in soybean, the researchers’ latest studies have involved Roundup Ready 2 Xtend soybean, which has tolerance to both glyphosate and dicamba; it is expected to be available to growers in the near future. Their experiments are showing very good control of GR giant ragweed – and also GR Canada fleabane – with tank mixes of dicamba and glyphosate applied preplant or in-crop.
Sikkema’s group has a large program on GR Canada fleabane control. He notes, “We can get quite good control in corn and wheat, but it’s a huge challenge in soybean.”
In corn, they are testing preplant and post-emergence options tank mixed with Roundup. In the preplant treatments, the dicamba-based herbicides Banvel, Marksman and Battalion gave greater than 90 per cent control. Callisto + atrazine and Integrity provided 80 to 90 per cent control.
Likewise, for post-emergence treatments in corn, the dicamba-based herbicides all gave greater than 90 per cent control. For Pardner + atrazine, control was between 80 and 90 per cent.
For GR Canada fleabane control in winter wheat, Infinity, Lontrel, Target, Dyvel, Banvel and 2,4-D ester were the most effective. However, Sikkema cautions, “Although Banvel, Dyvel and Target are very effective on GR Canada fleabane – and also on GR giant ragweed – I am reluctant to recommend them because I think the margin of crop safety in winter wheat is too narrow; you can incur yield losses due to crop injury.”
In soybean, the researchers have looked at a wide range of herbicides, but are finding it very hard to get consistent control of GR Canada fleabane. For example, in their enhanced burndown experiments, “The tank mixes of Roundup plus Eragon, Integrity, 2,4-D, Liberty, Gramoxone, FirstRate and Classic all have activity, but the range in control can be very wide from field to field,” says Sikkema.
“We’re continuing to do research on this. We’ve done over 20 experiments and haven’t yet found out what the contributing factors are causing this variability in control.”
In their burndown plus residual treatments in soybean, the most consistent control of GR Canada fleabane was with Roundup + Sencor applied at the highest label rate registered in Ontario. “However, at that rate you get crop injury on light-textured soils, you could have sensitive cultivars that contribute to crop injury, and it’s simply too expensive,” notes Sikkema. Tank mixes of Roundup plus FirstRate or Broadstrike RC are also effective, but, in some fields, there are multiple resistant Canada fleabane and these tank mixes will not control those biotypes.
In the post-emergence treatments in soybean, the best results were with Roundup + FirstRate. But Sikkema cautions, “From our work, we know that 12 per cent of the fleabane in Ontario is resistant to both glyphosate and FirstRate. We had from 20 to 90 per cent control with FirstRate, and I think that is a function of whether it’s GR Canada fleabane or if it’s multiple-resistant Canada fleabane.”
He adds, “We have no effective post-emergence options in soybean for multiple-resistant Canada fleabane.”
One of Sikkema’s graduate students, Annemarie Van Wely, has just finished a study of GR common ragweed that included herbicide treatments in soybean.
“In her enhanced burndown experiment, she looked at every possible tank mix that is registered [in Ontario]. She found that Roundup + Eragon was the most effective, but the control was only 72 per cent,” notes Sikkema.
“In her burndown plus residual treatments [using tank mixes with Roundup], Lorox and Sencor gave greater than 80 per cent control. Integrity and Optill provided between 70 and 80 per cent control. However, the Lorox and Sencor treatments were applied at the highest label rate registered in the province. I think farmers will be reluctant to use them at those rates because they are expensive, they can cause injury on light-textured soils, and there could be cultivars sensitive to Sencor.”
In Van Wely’s post-emergence treatments, Roundup + Reflex gave the best results with between 70 and 80 per cent control of GR common ragweed.
Based on these results, it appeared that a two-pass approach would likely be needed for effective GR common ragweed control. So Van Wely applied tank mixes of Roundup with one of Integrity, Lorox or Sencor, prior to soybean emergence, and then applied Roundup + Reflex post-emergence. That combination gave between 85 and 95 per cent control of GR common ragweed.
Exploring non-herbicide options
Non-chemical weed control options can be important for dealing with GR weeds, especially if they have resistance to multiple herbicides.
A number of Ontario studies are underway on such options. For example, Tardif is leading a project with Ontario Ministry of Agriculture and Food and Ministry of Rural Affairs weed specialist Mike Cowbrough to assess crop management approaches to reduce weed seed production in situations where weeds aren’t effectively controlled by a herbicide. “The weeds may be herbicide resistant, or the herbicide may not have lasting power in the soil to stop the weed seeds from germinating, or the weed’s biology may allow it to germinate later on,” explains Cowbrough.
The project, established in 2014, involves four cropping rotations. It is assessing the effects of crop type, seeding rate, fertility and cover crop practices on weed seed production and crop yields in corn and soybeans.
Cowbrough says, “We’ve coined the project ‘To Fight the Light’ because our goal with each cropping system is to cover the soil almost 100 per cent of the time so light isn’t touching the soil and stimulating new weed seed germination.”
He suspects it will take several years before the effects of the different treatments on weed seed production become clear. “It is something that really struck me recently when I spoke to three Australian producers [who were dealing with serious herbicide-resistant weed issues]. No matter what non-chemical strategy they used, they all said it took about five to six years before they saw meaningful differences in weed populations because there had been such high weed seed deposition in previous years.”
With such a long lag time until results appear, the researchers want to be sure the practices are cost-neutral. Cowbrough says, “For instance, let’s say I could demonstrate that a 10 per cent increase in your seeding rate in corn would dramatically reduce the amount of weed seeds and that the increased corn seed cost would be paid back in higher yields, but it will take five years to see a weed control benefit. There’s a higher probability of people adopting that practice than if you have to spend $35 per acre on a practice and you won’t see a weed control benefit from it for five years.”
According to Cowbrough, Dr. Eric Page with Agriculture and Agri-Food Canada (AAFC) at Harrow will be joining the To Fight the Light project in the future. Page is working on similar research on giant ragweed, including GR giant ragweed.
In another project, Page and AAFC’s Dr. Rob Nurse are testing a prototype of the Harrington Seed Destructor that AAFC has purchased. This machine was developed by Ray Harrington, a crop producer in Australia, as a tool for managing weeds with resistance to several herbicides (see ‘Australia’s fight against herbicide resistance’ on page 32). The Destructor crushes weed seeds that come out of the combine with the chaff. The researchers want to see how well it works in Ontario’s crops with Ontario’s weed spectrum.
Reducing the risk of resistance
Sikkema emphasizes that preventing glyphosate resistance is quite straightforward. “We have to apply glyphosate less frequently. It is as simple as that.”
To reduce reliance on glyphosate, he recommends adding diversity into your weed management programs. “Include multiple crops in your rotation, including some that are not Roundup Ready, so that you won’t be applying glyphosate post-emergence in the crop. You still could put it on preplant as your burndown or as a pre-harvest or post-harvest application,” says Sikkema.
“If you are growing Roundup Ready crops, then I suggest a two-pass weed control system. In the first pass apply a broad-spectrum, soil-applied herbicide that has activity on the primary grass and broadleaf weeds on your farm. Then watch the field and decide whether or not you need a post-emergence application of glyphosate.”
Sikkema also suggests using tillage to control weeds at strategic points in your crop production system, although it’s important to avoid excessive tillage which can lead to soil erosion, breakdown of soil structure and other problems. And he recommends, “Use excellent crop husbandry, whether that’s using well adapted cultivars or hybrids that emerge quickly and outcompete the weeds, using the right seeding rates, possibly reducing soybean row widths so the canopy closes earlier, controlling insects and diseases, using proper fertility – anything you can do to make the crop more competitive with weeds.”
Cowbrough has two pieces of advice for reducing the risk of herbicide resistance. First, focus on the most prominent weed species on your farm. “The bigger the weed’s population, the more likely it is that you will select for a resistant biotype if you apply that selection pressure. And if it’s a species that is more prone to being selected for herbicide resistance and its seed is mobile, then the risk will be higher.”
And second, use more than one strategy to attack those prominent species. “That could mean the addition of two or more herbicide modes of action, using some cover crops, doing some tillage, and so on.”
As Dr. Mike Owen, longtime professor and weed scientist at Iowa State University, sees it, Iowa is a desert of corn and soybean. Iowa has approximately 14 million acres of corn and 10 million acres of soybeans. The two crops represent about 70 per cent of the landmass in the state of Iowa. And often, corn is grown back-to-back as growers chase the highest economic return.
“The problem that we have is that we are truly lacking in diversity. Consider that this type of non-diverse environment over such a large scale has overriding implications on pretty much everything,” says Owen, who spoke at the Manitoba Agronomist Conference at Winnipeg, Man. in December 2013. “I dare say it is inevitable unless you are smart about the changes that you make.”
Owen says the changes to production agriculture in Iowa are driven not so much by agronomics, but by economics and sociological changes. The political discussion around ethanol has driven the growth of corn production and revenues, skewing rotations away from diversity and impacting agronomic decisions made by growers and professionals.
“Even when looking at soybean prices of $14 to $15 per acre, we were still making more money growing continuous corn, which gets us further down the bad trail with regard to diversity and pest management,” he says.
In Western Canada, there is currently a more diverse rotation than Iowa’s rotation of Roundup Ready corn and soybean or continuous corn. However, rotations have begun to tighten up in Western Canada, with wheat and canola (approximately 50 per cent Roundup Ready canola) the most common rotation, and in some instances, continuous canola. That diversity is also changing with the increasing Roundup Ready soybean acreage in Manitoba and Saskatchewan, and an increased breeding focus on short season Roundup Ready corn for Western Canada.
“Predictably, because of this lack of diversity, pests – not just weeds, but pests – are evolving resistance to the strategies that growers are willing to use to manage them,” says Owen. “Interestingly, [farmers in Iowa,] Manitoba, Canada, Honduras, the thought process is very much the same. We are doing stuff because of the tools that are available; we’re creating the problems that we have.”
In Iowa, Owen says weeds are the most consistent problem, more than any other pest complex, because they are always there and farmers are always trying to control them. Waterhemp, an amaranth species, has populations with resistance to five different herbicide groups including Group 9 glyphosate. Horseweed/marestail and giant ragweed have also evolved resistance to Group 2 and 9 herbicides.
The corn rootworm complex is starting to evolve resistance because one of the management strategies for the rootworm complex was rotation between corn and soybean. Now with continuous corn and the use of Bt and multiple Bt genes, the selection pressure is causing an evolution in resistance. Owen says growers are now going back to the “good old days” of soil-applied insecticides because of evolved resistance to Bt.
“It comes as no surprise to me that the phenology of the rootworm is pretty much similar to the phenology of weeds, which is not terribly different to the phenology of the cyst nematode. It kind of stays in one place, moves around a little bit, but the selection pressure is similar. So we’re beginning to see the system, as it moves to less diverse, simpler, more convenient approaches, the system is pushing back.”
The evolution of weed control
Like Charles Darwin’s evolutionary theory, where selection pressure initiates changes in species, the same concepts of selection and evolution of the pest complex in agriculture is occurring, but at warp speed. Owen says from the early 1900s through to today, agricultural practices in Iowa have eliminated most of the cultural and mechanical pest control practices. He says at one time, crop rotations, herbicide rotations, tillage, row spacing and planting dates helped with weed control. Now, at least in Iowa’s case, growers rely primarily on one herbicide, glyphosate, for weed control. Since the introduction of Roundup Ready crops in the U.S. in 1996, the market share of glyphosate resistant soybeans, corn, cotton and sugar beets is all over 90 per cent.
“We have almost eliminated diversity in our crop production system,” says Owen. “This is not to say that glyphosate isn’t a good herbicide. This is not to imply that the technology is not good. But like any other tool, the technology has to be used in a manner that is sustainable.”
Owen says the shift to the reliance on only herbicide for weed control comes down to economics and time management. Drivers of this change are increasing farm size where owners and agronomists have less time to manage a diverse cropping system. He says the average land price in Story County in central Iowa went up 15 per cent in 2012 and five per cent in 2013 and sat at $9,000 per acre. Further north and west it is $12,000 to $15,000 per acre. Large farms are on the increase and mid-sized farms are being eliminated.
“The ones with large areas don’t have time to manage anything. They make more money managing the grain crop and marketing of the crop than making the technical decisions on how to grow a crop. They are looking for simplicity and convenience. The siren song of those two are driving the system where they don’t have the time to do things correctly,” says Owen.
In Iowa, glyphosate is used on almost 100 per cent of all soybean acres and 90 per cent of corn acres. There is a bit of a recent increase in other herbicide use in soybean and corn, but in Iowa, out of 24 million acres, an estimated nine million acres have only glyphosate applied. Glyphosate is the primary if not sole selective factor for weed resistance.
Owen says the system is, predictably, pushing back. There aren’t a lot of train wrecks, but resistant patches are showing up in many fields. “We did a random survey of 400 fields in Iowa last year, and what we found was that 70 per cent of soybean fields had weeds above the canopy. You see that in August and September and something bad happened.”
Once a herbicide-resistant population is noticed by growers, it has become large. Research has shown that before herbicide resistance is noticed in a field, approximately 30 per cent of a weed population has evolved resistance.
“So you’ve gone through a number of reproductive cycles, and now the seed bank is full of resistant individuals. Once it goes from additive to logarithmic, the change will happen incredibly fast,” cautions Owen.
A 2011 study of 400 samples of waterhemp populations shows the worst-case scenario for Iowa growers (the samples weren’t randomly selected). Sponsored by the Iowa Soybean Association, the study found waterhemp was resistant to five different herbicide groups. Around 96 per cent were resistant to Group 2 (ALS inhibitors), just under 60 per cent to Group 5 (triazine), around 55 per cent to Group 9 (glyphosate), just under 10 per cent for Group 14 (PPO inhibitors) and 25 per cent demonstrating resistance to Group 27 (bleaching).
Each population was also screened with all five herbicides. Owen says, not surprisingly, that one third of the populations were resistant to all three of the following herbicides: Group 2 (ALS herbicides from the heyday of the 80s and 90s); Group 5 (atrazine, still the second most widely used herbicide); and Group 9 (glyphosate, the most widely used herbicide). And about five per cent of populations were resistant to all five herbicide groups.
“If you are a grower, or helping your grower, trying to come up with a management program that is convenient and simple and economic, it is getting increasingly more difficult. Right now in Iowa, 88 per cent of waterhemp has multiple herbicide resistance,” says Owen. “We got there because of the decisions that were made without an overriding understanding of the repercussions of the decisions.”
Glyphosate resistant giant ragweed has also become a problem in Iowa, and has been identified in Ontario. In the Mississippi delta in southeast U.S., glyphosate resistance is a problem in Palmer amaranth, which has moved up into Iowa in contaminated feed. It is a desert plant, but has adapted to the Midwest U.S. and could adapt further north.
In Manitoba, 11 weed species have been identified with herbicide resistance. Most of the broadleaf weeds are resistant to Group 2 ALS inhibitors, but wild mustard has also shown resistance to Group 4 Synthetic Auxins and Group 5 triazines. Additionally, a 2013 survey of 283 different kochia populations in Manitoba found two populations resistant to glyphosate.
“I see a lot of Group 2 resistance [in Manitoba], but I am more interested in the specific weeds that might adapt well to corn and soybean production. Green foxtail; kochia, which is becoming a poster child in the west for herbicide resistance; Palmer amaranth; redroot pigweed. My point is that you are already part way there. You just need to shift things a little bit more the wrong way and you’ll end up in a bad situation unless appropriate management is applied,” cautions Owen.
Owen starts with scouting as a foundation for weed control. Especially in Iowa where fields have many different resistant populations, scouting helps identify what effective herbicides are left for a particular field.
On all acres across all crops, weed specialists are promoting an effective pre-emergent treatment with multiple modes of action. He cautions that multiple modes must be effective on the weed biotypes in the field. In Iowa, many herbicide products contain a Group 2, but many weed populations have Group 2 resistance so growers must make sure their herbicides include additional modes of action that are effective. The direct parallel in Western Canada is kochia, where weed scientists assume all populations to be resistant to Group 2 herbicides, and other Groups should be included in a pre-seed burndown with glyphosate to help manage herbicide resistance.
Effective and timely post emergent herbicide applications seem like a given, but Owen cautions that growers need to target herbicides to protect yield, not control weeds. Otherwise, they are unnecessarily putting selective pressure on weeds.
“We have lost untold money by effectively killing a lot of weeds with glyphosate. We kill a lot of weeds in Iowa with glyphosate, but [not until] after they have competed with the crop and we have lost significant yield potential never to be gained.”
A diverse crop production system is key to controlling weeds and prolonging effective herbicide life. Owen sees problems on the horizon for western Canadian growers who are growing Roundup Ready corn and soybean in tight rotations.
“You need to start thinking about weed control and weed management, not just for this year, but you need to start thinking about what you are going to do three or four years down the road, and have a plan, and have a what if it doesn’t work, what will I do, what will it cost? You need to have that kind of plan to maintain that diversity,” he says.
Inevitably, without diversity, herbicides will fail. Weeds can even adapt to tillage. Waterhemp avoids cultivation by delaying germination.
In Iowa, Owen would like to see a more balanced approach to weed control that includes cultural, mechanical and herbicidal weed control tactics. He believes herbicides will remain an important tool in the foreseeable future, but they need to be supported by other control methods.
“And that’s a problem, because for growers in Iowa, we are so large, and so accustomed to simplicity and convenience that they can’t remember the way it was,” says Owen. “In fact, we have a whole generation, referred to as ‘Roundup Babies,’ who have never sprayed a herbicide other than glyphosate. They don’t know another herbicide exists.”
Owen recognizes that adding diversity isn’t easy for growers in this era of large farms and the drive for simple, convenient and profitable farming systems. He is working with rural sociologists and agricultural economists trying to figure out what kind of changes growers can make and still be profitable.
“Basically what I am suggesting is you need diversity, and if you choose not to have a more diverse system, then understand the inevitability of the failure with regards to weeds adapting. That will happen.”
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