There is a lot happening out there. I am sure I am not aware of half of the infestations that are going on but at least I will report on what I do know.
Western bean cutworm – Hot spot egg mass locations continue to be in the Bothwell area with now fields in the Tillsonburg area also showing up with significant pressure. Many other fields in southern Ontario have a low number of egg masses in them right now but with moths numbers continuing to climb in our traps, I suspect more egg laying will take place this week and next. Unfortunately much of the corn crop is in the ideal growth stage to attract moths to lay eggs. Scouting is advised. Do not make a spray decision without scouting the field first to know that you are at or above threshold. Moths are still coming in and premature sprays may miss the peak egg laying in your field. We will let you know when peak moth flight occurs (last year it was next week but I suspect we will be a little behind this year).
Soybean aphids – Hot spots of near to over threshold infestations have shown up, particularly in the Shakespeare to Mitchell area. Also north of London near Arva and Ilderton. Most of higher infestations are in fields that were planted early without Cruiser but even early fields with Cruiser are now seeing populations start to build. Over the last two weeks, many other early and late planted fields distributed across Ontario have aphids in them now (too many to list). This is the second wave so to speak of aphid infestations where summer migrants have moved in from other regions to start colonies in new fields. If they arrive in fields with few predators, populations can rise quickly. Fortunately this very hot weather should slow the aphid development down, particularly since crop canopies have not full closed in many cases to make it cooler. But this doesn’t mean they can’t get out of hand on you. Plus the crop is extra stressed right now so spraying closer to just past threshold is advised (if predators are not in great numbers) rather than waiting to get closer to 500-600 aphids per plant which is acceptable in a healthy stress free year.
Spider mites – I have not heard of any reports of spider mites yet but they have got to be out there. In both soybeans and even seed corn, I expect to see mites flare up quickly with this hot, dry weather. Look for signs of plants along the fields edge turning bronze and looking somewhat sand blasted. Look for mites on the underside of those leaves. Spot sprays along the fields edge where these mites are starting up can often keep you from having to spray the entire field.
Keep in mind daytime temps are extremely hot for applying most insecticides. You are better off waiting to the end of the day when temps cool down if spray is warranted.