Insect Pests
A groundbreaking new method for controlling flea beetle, the pest that causes at least $300 million in damage in North American canola every year, may hit growers’ fields early in the next decade.

RNA interference, or RNAi – a process by which RNA molecules “silence” genes targeted as threats – has already been harnessed by public and private research and development programs against several agricultural pests, including Colorado potato beetle (CPB) and corn rootworm.

According to Jim Baum, Monsanto’s insect control lead in chemistry, the use of RNAi technology against flea beetle “represents a sizable opportunity and need” for canola growers in the U.S. and Canada who have seen incomplete protection from neonicotinoid insecticides and other chemical products in recent years.

Monsanto began work on an RNAi-based product for flea beetle control several years ago, Baum says, as part of a suite of RNAi projects aimed at controlling agricultural pests, including corn rootworm and CPB.

Put simply, RNAi for flea beetle control works by “tricking” the beetle’s natural immune system to self-destruct. Beetles are fed double-stranded RNA (dsRNA) molecules that “turn down” expression of a critical gene in the flea beetle midgut, killing exposed insects within five days.

There are two possible delivery methods for RNAi-based pest control in agriculture: plants can be genetically engineered to express dsRNA in their leaves, or dsRNA can be applied externally to plants as a topical spray. Monsanto has worked with both methods; its corn rootworm product is transgenic.

But the company’s flea beetle project is currently focused on the development of a foliar insecticide that can be applied using its patented BioDirect platform.

Monsanto advanced its CPB BioDirect product to Stage 2 in 2015, and Baum says the company’s experience in RNAi for CPB control has streamlined its approach to new RNAi products.

The company has already run lab bioassays monitoring mortality in insects fed various dsRNAs, as well as seedling assays in which a set number of beetles are exposed to canola seedlings treated with dsRNA at a prescribed field rate.

Last year, Baum says, Monsanto ran successful field trials for its flea beetle RNAi project, and this year the number of trials more than doubled. (The company could not comment on the location of the field trials).

Next up, Monsanto will be analyzing effectiveness of various agronomic practices — basically, what works best in terms of rates and application timing, and how the product will work in combination with other products.

“Compared to previously approved products’ timelines, we’re being conservative with this one, recognizing that topical is a new application of the technology,” Baum says. “But if the project is successful, we’re projecting commercialization sometime on the early side of the next decade.”

Farmer and consumer outreach
Though RNAi-based insect control products won’t reach farmers’ fields for several years, they need to know what’s coming, and farmer and consumer outreach will be more important than ever for companies looking to commercialize the technology.

This is the view of Curtis Rempel, vice-president of crop production for the Canola Council of Canada.

“RNAi provides a tool or a technology that takes us outside of the traditional chemistry realm, so it has the potential for much improved environmental outcomes, but along with new technologies come a new set of regulatory and efficacy evaluations,” he says.

Just how safe is RNAi? According to Baum, RNAi has a built-in specificity that means once dsRNA is targeted to a specific insect pest, even closely related pest species are not harmed when they ingest it. “It’s hard to imagine a chemical insecticide, even Bt, that would be as specific as this RNAi product we’re talking about here,” he says.

Rempel agrees but believes farmers and consumers alike need to feel that regulators and scientists have had the opportunity to evaluate RNAi technologies in terms of environmental and societal norms.

Next year, the Canola Council hopes to include discussions around RNAi in its annual Canola Discovery Forum, and Rempel says the organization is working on developing “supporting material” to help communicate the role of RNAi in pest control to stakeholders – although he is quick to point out that communications outreach about RNAi requires the collaboration of all stakeholders.

In Rempel’s estimate, only 10 per cent of farmers are familiar with RNAi and aware of projects in the pipeline, even though they are the ones who will benefit most from its use.

But consumers shouldn’t be neglected either. After all, it’s consumers who implicitly afford farmers the “social license” to use technologies like RNAi, and they are the ones who will need to be assured of the products’ safety.

“I think we have an opportunity to do a good job of looking at the questions we’re asking, reviewing regulatory procedures and communicating these to the layperson,” Rempel says.

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The yield potential of hybrid canola continues to push higher, begging the question of whether economic thresholds for lygus bug developed in the 1990s are still valid today. With more vigorously growing crops, higher yield and relatively high canola prices, new research has found the current economic threshold level of approximately one lygus bug per sweep to be too low.

“Economic thresholds for the early pod stage were developed in Manitoba in the mid-1990s and were based on conventional canola varieties like Westar. However, since then a number of new hybrids, including herbicide-tolerant cultivars with superior agronomic traits, have entered the market and been adopted extensively,” says Héctor Cárcamo, a research scientist with Agriculture and Agri-Food Canada (AAFC) in Lethbridge, Alta.

Cárcamo and colleagues at AAFC Lethbridge, Lacombe and Beaverlodge conducted several research studies from 2012 through 2015 to validate economic thresholds for lygus in southern and central Alberta using a hybrid cultivar. They compared the impact of lygus feeding on current hybrids of canola and a conventional cultivar, and obtained baseline information about lygus in fababeans. The research was funded by the Alberta Canola Producers Commission, Alberta Pulse Growers, Alberta Crop Industry Development Fund and AAFC’s Pest Management Centre.

A multi-site cage study was completed near Lethbridge and Lacombe to assess how lygus affects yield in canola for current cultivars and to refine thresholds. The cultivar L150 was planted at both locations. One-meter square cages (1.2 and 1.5 m tall, at Lethbridge and Lacombe, respectively) were used to confine 75 plants. The treatments included an uncaged area, and caged densities of zero, four, 10, 20, 50 (40 in Lacombe) and 80 lygus. In year two in Lacombe, an extra treatment was added in each cultivar to compare two lygus species (L. keltoni and L. lineolaris) at a density of 20 bugs per cage. At Lethbridge, the treatments included additional treatments with seedpod weevils at 10, 20 and 40 per cage, as well as a combination of 10 lygus and 10 weevils per cage, to assess the joint effects of these two insects at moderate densities below threshold.

Economic threshold increased to two to three lygus per sweep
Cárcamo says the insect additions were successful in establishing a gradient of different lygus densities, and allowed an assessment of yield impact and economic thresholds.

“The outcome of the studies suggests that the current economic threshold of one lygus per sweep at the early pod stage is too low. For Lethbridge, the data suggested that canola yield losses to warrant control did not occur until lygus reached around three lygus per sweep. For the Lacombe region, the threshold was around two per sweep,” says Cárcamo.

A second study was conducted at AAFC Beaverlodge from 2012 to 2015 to look at damage and yield comparisons in three canola varieties from bolting to maturity. InVigor and Roundup Ready hybrids were compared to Westar. Lygus adults were collected by sweep-net from local alfalfa fields and sorted by species. The dominant species of lygus was then used to stock cages at the late rosette stage with 20 adults.

The results for Beaverlodge were less conclusive, but a comparable impact of lygus on canola was observed and a similar threshold could be applied for Lacombe. More site-year data are needed to relate weather to lygus damage, but for Lethbridge, the highest number of lygus per cage (more than 1,000) and extreme yield loss (40 per cent) occurred in July 2012, when temperatures were hot (mean of 20 C) and dry (lowest rainfall relative to other years). In a normal year with sufficient rain – meaning a normal mean temperature below 20 C in July and greater than 120 millimeters of rain in June and July – lygus bugs at low populations of one per sweep did not pose a yield risk.

Cárcamo explains that in a field situation, the yield loss could also be lower because lygus in open fields are subjected to higher predation by natural enemies and also suffer more disturbances from rain and wind, unlike the situation in a cage. This means the estimates of lygus bug damage could be exaggerated and the thresholds could be even higher. Another four-year study funded by the Canola Council of Canada’s Canola Agronomic Research Program (CARP) is underway across the three Prairie provinces to attempt to validate these thresholds in actual commercial canola fields.

Cárcamo says using a higher threshold, even if only slightly higher, may result in a large reduction in pesticide use in canola crops and produce significant cost savings for canola growers. Such a reduction may have other positive repercussions, such as increased activity by pollinators and other natural enemies, which provide beneficial ecosystem services.

“On the other hand, if lygus reach or surpass three per sweep in the south, there are significant economic returns to be realized by spraying because our results, despite high local variability, showed that lygus can reduce canola yield by about 15 per cent in most years in southern Alberta and up to 20 per cent in central Alberta,” Cárcamo says.

Fababean thresholds also evaluated
In fababean there are concerns that lygus feeding can increase necrotic spots, reducing quality and marketability in addition to potential yield. At AAFC Lacombe and Vuaxhall, both in Alberta, a study was conducted to assess the species and crop damage that occurs on fababean from lygus bug feeding. In Lacombe, two to 10 fields of tannin cultivars and six to 11 fields of zero tannin fababeans were surveyed from 2013 through 2015 with sweep nets at the bud, flower and pod stages. In total, 43 fields were sampled. Lygus were identified by species and nymphal stage and total numbers were recorded.

Field and plot studies showed a similar species composition of lygus and activity pattern compared to canola. In most fields, lygus were present at less than one per sweep and rarely two or more per sweep at any crop stage. Cárcamo says further studies are needed to make management recommendations, but as a guideline, farmers may take control action if there are more than two lygus per sweep. He adds farmers should attempt to mitigate any impacts on pollinators and natural enemies of lygus.

“Fababean requires pollinators to improve yield, so it is crucial to mitigate insecticide impacts on them or the action could also affect yields negatively,” Cárcamo says. “Planting early is recommended to avoid the peak of damaging lygus populations that occur late in the growing season.”

Top tip: Sweep net sampling for lygus bug
Take 10 180-degree sweeps with a standard insect net measuring 38 centimeters (15 inches) in diameter, and aim to sweep the canola buds, flowers and pods while moving forward. Count the number of lygus in the net. Sampling several locations in the field and taking more sweeps will provide a better assessment of pest populations. Samples can be taken along or near the field margins. Sample the crop for lygus bugs on a sunny day when the temperature is above 20 C and the crop canopy is dry.

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Swede midge first appeared in canola in Ontario in 2003, and recent extreme populations in northeastern Ontario resulted in the Ontario Canola Growers’ Association (OCGA) strongly recommending in 2015 that producers avoid growing canola for three years across the New Liskeard area in an attempt to suppress swede midge populations.
The number of bertha armyworm larvae on a farm last year is not a reliable indicator of what to expect this year. Bertha armyworm populations fluctuate widely from year to year.

Provincial monitoring programs raise awareness of potential outbreaks, based on number of adult moths caught in pheromone traps. Adult counts in June and July can indicate the risk of larvae feeding in July and August. Begin larval monitoring after peak flowering or about two weeks after peak trap catches. Continue scouting until either the mean number of larvae per square foot exceeds the economic threshold (at which point the crop is sprayed) or until the time remaining until the crop is swathed no longer allows for application of a registered insecticide based on the allowed pre-harvest interval.

Often bertha larvae aren't noticed until they move up the canopy and are easily visible during mid to late podding. At this point, chewing on the pods causes visible yield loss quickly. They will lower in canopy before that time, feeding on lower leaves. Assessing your crop early for telltale signs of leaf feeding and becoming aware of your forecast risk will give producers time to accurately assess and time an insecticide application, if needed.

Scouting tips
— Go out in early morning or late evening when larvae are mostly active.
— Mark out an area a quarter-metre square (50 cm by 50 cm) and beat the plants growing within that area to dislodge the larvae. Count the larvae that have fallen to the ground and multiply by 4 to get the number per metre square. Larvae will hide under leaf litter and in cracks, so check closely.
— Sample at least 5 locations (10-15 is recommended) a minimum of 50 metres apart. Do not sample headlands and areas within the crop that are not representative of the field. Use the average number of larvae at the sites surveyed to determine if the economic threshold has been exceeded.
— Scout each field. Adjacent fields may have very different larval densities, depending on how attractive the crop was when the moths were laying their eggs. Adjacent fields may also have different-sized larvae, depending on when the eggs were laid.
— For best results, apply an insecticide as soon as economic thresholds are reached. A single well-timed application of any registered insecticide is usually effective. Check provincial crop protection guides for registered insecticides.
— Apply insecticides early in the morning or late evening when the larvae are actively feeding. Do not apply during warm afternoons.

Click here to see a video of Alberta Agriculture and Rural Development's insect management specialist, Scott Meers, demonstrating how to scout for Bertha armyworm larvae in the field.
Globalization of the Arctic, emergence of invasive microbial pathogens, advances in genomic modification technology, and changing agricultural practices were judged to be among the 14 most significant issues potentially affecting how invasive species are studied and managed over the next two decades. | READ MORE
A Canola Agronomic Research Program (CARP) project on cutworms is now completed, resulting in "The Cutworm Booklet," which will help producers identify and control cutworm species, and give them a better understanding of the role of natural enemies in the control of the various cutworm species.
Set out a free smorgasbord and see who shows up. In the case of fababean, as acreage has risen, pea leaf weevil and lygus bug have been coming to dinner. For producers, the main concern with pea leaf weevil is feeding on nitrogen-fixing nodules, while for lygus bug, the economic impact is related to seed quality.
Cutworm management starts with identification – knowing what species is at work in your fields helps unlock information that improves cutworm scouting and management. Knowledge of cutworm biology, behaviour, preferred habitat, impacts of weather and interaction with its natural enemies will all improve scouting techniques and pest management decisions for growers.

The Cutworm Pests of Crop on the Canadian Prairies - Identification and Management Field Guide describes the economically important cutworm pests in detail and provides the information needed to manage them.
The first Prairie-wide risk and forecast maps are now available from the Prairie Pest Monitoring Network blog. They can be veiwed and downloaded here. Maps are generated for bertha armywork, grasshoppers, wheat midge, cabbage seedpod weevil, pea leaf weevil, wheat stem sawfly, diamondback moth as well as average temperature, average precipitation and modeled soil moisture for the Canadian Prairies. 
When the cereal leaf beetle (CLB) was first spotted in Alberta in 2005, the then-regulated pest was met with consternation by western Canadian producers. CLB can cause significant damage to all crops in the grass family, even forages, and yield losses in affected areas of the United States have reached 50 per cent.
A dry spring hindered crop growth and gave a leg up to early season insects like cutworms and flea beetles in some areas of the Prairies in 2016. Mid-season growing conditions favoured wheat midge.
For potato growers in Western Canada who are nervously watching the progress of potato psyllids (Bactericera cockerelli) moving in from the northwest United States, there’s good news: none of the potato psyllids found in Western Canada are carrying the zebra chip pathogen, Candidatus Liberibacter solanacearum (Lso). The Lso pathogen is transmitted by the potato psyllid, and zebra chip has caused severe damage in potatoes in the western United States, Mexico, Central America and New Zealand.
Soybean aphids have become well established throughout the northern Midwest United States and the provinces of Ontario and Quebec, causing significant damage in some years.

Because of the potential for ongoing problems from this yield robber in the future, there have been significant funding efforts from research programs: One management strategy has been to develop soybean varieties that are resistant to soybean aphids.

“The checkoff in Ohio as well as the North Central region states have put in a lot of investment in developing soybean plants that are resistant to the aphids, but now we have aphids that have overcome that resistance,” said Andy Michel, field crops entomologist at Ohio State University.

To address this challenge, researchers took on the extensive process of sequencing the entire soybean aphid genome to help develop strategies that prevent the spread and increase of aphids capable of breaking aphid resistance. Michel led the effort.

“My laboratory at Ohio State focuses on understanding how soybean aphids are able to overcome aphid resistance in soybean. Through this research, we hope to develop strategies that prevent the spread and increase of aphids capable of breaking aphid resistance. In the course of generating DNA sequences…we were able to sequence the entire soybean aphid genome,” he said. “We now have a really good roadmap for the soybean aphid and understanding all of the genes that are involved that make the aphid such a bad pest for soybean farmers in the north central region.”

The soybean aphid is now the fourth aphid species with a completely described genome and this new information will be a valuable tool moving forward with soybean aphid management. | READ MORE
“The pea leaf weevil has been a traditional pest for many years, and there is a lot of these pests in Canada,” says Gadi V.P. Reddy, entomologist of Montana State University’s Western Triangle Agricultural Research Center (WTARC). “The pea leaf weevil spread across the pulse growing regions in 2012, increasing problems caused by the pest.”

Reddy spoke at WTARC field days about his pheromone research project. Reddy has grant funding under the Montana Specialty Block Grant program, in cooperation with the Montana Department of Agriculture and USDA-National Institute of Food and Agriculture (NIFA), for the pea leaf weevil pheromone project to attract the pea leaf weevil.

There are two generations of pea leaf weevil per year, but the second generation of adults don’t cause damage like the first generation. During winter, the weevil hibernates under debris leaves and emerges in the spring, usually around May. When the pest emerges in spring, the adults feed on pollen and nectar on leaves; then they mate and the females lay eggs on the seedlings of peas and lentils that emerge as larvae. The larvae or grubs burrow deep in the soil and feed on roots and root nodules, causing damage. Plants fix less or no nitrogen when the roots are damaged, and sometimes the plant itself dies.

Reddy experimented using baited aggregation pheromone traps in the field to help monitor and mass trap weevil populations. He found that the pitfall traps worked the best at catching pea leaf weevils. These traps are a container that is sunk into the ground so that its rim is flush with the soil surface. Insects simply fall into the trap. Reddy used a liquid aggregation pheromone to lure them.

Another pheromone lure type is a bubble wrap, placed in pea or lentil fields.

In these traps, growers use a small quantity of soap or detergent water so that the trapped weevil gets killed.

“We found a lot of pea leaf weevils in our pheromone traps in 2016. Next summer, we will determine how many pheromone-baited traps we need per acre to trap the weevils,” Reddy says.

In addition, WTARC will be developing biodegradable pheromone lures so that growers won’t have to take them out of the field after each season.

Reddy is also looking at bio-based insecticides to control pea leaf weevils.
The wheat midge forecast for 2017 shows an overall lower level of wheat midge across Alberta. There has been a slight bounce back from the collapse of the extreme populations in the eastern Peace region. Although wheat midge has not followed the forecasts very well in the Peace region, it's important to note that there are likely sufficient populations of midge in the eastern Peace to fuel a resurgence if conditions are in the insects favor (specifically delayed crops and higher than normal rainfall).

Central Alberta has some areas of east of Edmonton with high numbers of wheat midge. The population has remained low in much of southern Alberta with the exception of some irrigated fields. Producers should pay attention to midge downgrading in their wheat samples and use this as a further indication of midge risk in their fields.

Over the past several years the field to field variation has been very considerable throughout the province, especially in those areas with higher counts. Individual fields throughout Alberta may still have economic levels of midge. Each producer also needs to assess their risk based on indicators specific to their farm. | READ MORE


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