Baute Bug Blog

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.

Chris DiFonzo from MSU and I both have this pest on our radar.  I was hoping to see more areas get some of the rain that touched Ontario yesterday but sadly that didn’t happen.  It is typically a little early for mites given the stage of the soybean crop but with this heat and dry conditions, it won’t take much to see outbreaks.  As wheat is harvested, mites move into soybeans starting at the field’s edge.  Windy days then help carry them further into the field.  If conditions are hot and dry, spider mites flourish.  I haven’t heard of reports yet in soybeans but while you are scouting for aphids these next few weeks, keep an eye out for mites too.    I wrote a blog article about mites last year that you can glean more info from: http://bautebugblog.com/too-many-fields-with-obvious-spider-mite-damage/ And lots of information is also available in the OMAFRA Pub 811, Agronomy Guide for Field Crops at: http://www.omafra.gov.on.ca/english/crops/pub811/13soybean.htm#spider

Severe spider mite damage near London

Travelling the country side yesterday,  I saw too much spider mite damage going out of control in soybean fields that were easy to spot from my car.  Too many fields that still have some time to mature are seeing sure signs of spider mite activity.  Some are already too late to control, as the mites have already started to kill off the plants (picture provided).  But some are still at a stage of infestation that could make a world of difference if they were sprayed.

Spider mites are very hard on the soybean plant.  Their feeding eventually causes the plant to drop its leaves and prematurly die.  When infestations first start, individual leaves begin to look sandblasted or “dusty” on the underside of the leaf.  Infested plants start to take on a grey appearance in patches in the field.  If the infestation is allowed to continue, these patches eventually turn brown as leaves drop off the plant and the plants shut down and die.

Dimethoate (Cygon and Lagon) is the only product 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.  However, the days to harvest interval for the dimethoate products is 30 days so if spider mites are active in your field, control will need to take place in the next week or two.

It hasn’t been since 2002 that we have experienced this low of levels of soybean aphids.  Cross my fingers and knock on wood but I think we are going to get through the season without a problem.

That said, spidermites are starting to pop up in fields, particularly where it is starting to get a bit dry.  Scout perimeters and keep an eye out for plants and leaves that are bronzing or look sandblasted.  It is too easy to miss the mites and suffer a serious yield loss because of it.  Even the aphids don’t like to live on the mite infested plants!

With this kind of heat AND wheat harvest just around the corner, we should keep an eye out for spidermite activity in both seed corn and soybeans.

I put together a pretty detailed article last year in the CropPest Ontario Newsletter.  Visit it to familiarize yourself with what signs to look for.  It is very important to stay ahead of spidermite infestations and control them prior to wind carrying them further into the field, resulting in the entire field needing to be sprayed.

And with Diagnostic Days this week, blogs may be brief and few but I will try my best to keep you informed of any relevant pest issues that pop up.

Try to stay cool and hydrated this week.