Ontario field crop report: August 24
August 26, 2016 - Rainfall across much of the province last week has brought renewed vigor to many crops. Hay and pasture fields have greened up considerably, suggesting a chance for a decent 2nd/3rd cut and getting livestock back on pasture. Corn and bean crops have responded to the rainfall as well. While some yield potential has been lost the last few weeks with dry weather through pollination/flowering, the recent rains will allow much of the remaining yield potential to be met, which might not have been the case if the rains were delayed another week or two.
Harvest of spring cereals is wrapping up across the province. While winter wheat yields were generally above average for all classes, spring cereal yields are lower than average, particularly in central Ontario. Canola harvest is underway and to date appears to be an average crop, with the rains helping fill pods at the end of the season. Dry edible bean harvest is just beginning and yields are not yet reported. The lack of disease issues in this dry season is offset by issues with pod fill; many empty or partially filled pods have been observed. In many areas of the province the soybeans are quickly senescing and turning yellow. Pods seem to be filling as they should but harvest will likely be earlier than usual, especially where it has been dry.
Spider mite and access to dimethoate insecticide were concerns in weeks past, but rains have sufficiently knocked back the pest in most areas.
Preparing for harvest
With the dry conditions this season crop maturity is advanced in many fields and weed escapes were common with poor activation of pre emerge herbicides due to lack of rain. Crops are likely to dry down earlier and quicker than normal and thus be sure to be watching closely if late season herbicide treatments are part of your plan. While monitoring fields for maturity, do some scouting to assess late season disease or insect issues that might influence the timing of harvest or desiccant application. To decide which fields should be harvested first, assess corn for stalk rot issues that may lead to lodging, or ear moulds infecting sites where insect feeding has occurred. For soybeans and dry edible beans, look at areas that are yellowing or senescing earlier and consider what disease or other stress may have occurred. Is the soil type or pH different in that area? Take note of these locations so you can capture the variability next time you conduct your soil sampling and can refer to them over winter as you plan for next year.
While walking the fields you should also look for escaped weeds or changing weed populations that may indicate new problem weed species or resistance to herbicides. Collect seeds from any weedy plants that you think may have herbicide resistance and submit the samples to the University of Guelph (see more info at www.plant.uoguelph.ca/resistant-weeds/services/index.html) For dandelion, Canada fleabane, perennial sow-thistle, field bindweed, wild carrot, burdock and other biennial weeds, fall herbicide application can be the best way to gain control so make this part of your plan.
This year has been quite different than last year. Take the time to update your records on issues that occurred this season for comparison to other dry years.
Harvest aids in soybeans and dry edible beans
Dry edible bean harvest is upon us, and producers may be considering applying a pre-harvest herbicide to even up dry-down. For soybeans and edible beans, controlling escaped weeds will make harvest more efficient, can improve harvest quality and can provide better weed control in the following crop. First and foremost, when using a pre-harvest herbicide ensure that you carefully follow the label regarding product rate, application timing, and pre-harvest interval to prevent accumulation of herbicide residues in the seed. If shipments are rejected because they exceed the maximum residue limits (MRL), it can negatively impact trade in the long term.
Consult with your buyer before selecting a product because they may have restrictions in place. Authorization of glyphosate in the European Union was set to expire in June and re-authorization came in the form of an 18 month extension in the final days of discussions. For this reason some bean dealers may have restrictions on the use of glyphosate pre-harvest.
How effective are different pre-harvest treatments at “drying down” common weeds? There is limited public research comparing performance of pre-harvest treatments on different weed species. Dr. Peter Sikkema has conducted six trials over three seasons on edible beans and his results are summarized below. Regardless of treatment used, the expectation should be that the pre-harvest treatment will improve harvest efficiency but it will not result in a complete “dry down” of target weeds.
A table featuring visual control of lamb’s-quarters, ragweed, pigweed and foxtail 8 days after application of various desiccant treatments can be found here.
Pre-harvest herbicides will not speed the maturity of the plants or decrease seed moisture, but can shorten the time between crop maturity and harvest. For edible beans, pod colour change is the best indication of maturity; leaf drop and leaf colour are not good indicators. Once a herbicide is applied, late pods will not continue to mature so ensure the beans have the desired colour before application and are not green when split open.
Herbicide labels provide guidance around timing, but it can be tricky to visualize exactly what “80% of pods have turned” actually looks like. And different edible bean classes have different pod colour when beans are fully mature. An article has been posted to fieldcropnews.ca containing more information about pre-harvest aids and photos of dry edible bean plants from various market classes when they are ready for application of herbicides compared to when it is too early.
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