Soybean aphids – Eastern Ontario and the thumb of Michigan have been battling soybean aphids for some time now. This is ideal weather for them so I expect to start to see fields in SW ON noticing populations climb. That said, I have not given up on the natural enemies. I just want everyone to be on watch and take a look in fields these next few weeks. See past blog entries for further details on scouting methods etc: https://fieldcropnews.com/2013/07/soybean-aphid-populations-present-and-increasing-in-some-fields/
Spider mites – It might be surprising to some but there are parts of Ontario that are actually on the dry side. Now that wheat is starting to come off, spider mites will be moving into soybeans (and corn). In dry areas, they can get ahead of the crop and do significant damage. Scouting methods can be found at: http://www.omafra.gov.on.ca/english/crops/pub811/13soybean.htm#spider Dimethoate (Cygon and Lagon) is the only product that is registered on soybeans that will work on spider mites. Do NOT use Matador as it does NOT control spider mites and can actually cause the mite population to build up more quickly.
Holes in the Soybeans? Many Defoliators Out There: Many are starting to notice holes in leaves and wanting to know if a spray is necessary. Many different types of insects can feed on soybeans but RARELY do any of them cause enough damage to warrant a spray. It doesn’t matter what type of insect is doing that feeding, it comes down to how much feeding they are doing. And the important part is to not overestimate that feeding damage. Make sure to scout the interior of the field (not just the first 30 rows of field edge) AND pluck the leaves from the middle of the canopy, since most of the feeding is always at the top of the plant which makes it appear worse than the feeding really is. Soybeans compensate for the feeding on the top of the leaves by taking advantage of the addition sunlight now hitting the lower leaves because of those holes. See this past two page Diagnostic Days handout I made that shows some of the different defoliators, how to estimate defoliation and what the thresholds are: https://fieldcropnews.com/wp-content/uploads/Soybean-Foliar-Feeders-Diagnostic-Days.pdf
Western Bean Cutworm – We think peak flight just took place given some of the trap numbers have skyrocketed. Fields not in full tassel already need to be scouted, particularly those that are not planted with a SmartStax, Herculex or Agrisure Viptera Bt hybrid. Dry bean growers should also be starting to look for pod feeding in the next 10 days or so.