Though we know there were hot spots this year, including Bothwell to Strathroy and south of Tillsonburg, we encourage all corn producers to be scouting for ear damage over the next month.  Scouting will identify additional areas that had decent WBC pressure and are at risk of higher overwintering populations and therefore infestations again next year.  Scouting will also help in deciding whether to harvest the crop earlier, or to segregate grain from those fields to reduce risk of ear rot and vomitoxins.

Fields in the Bothwell area are seeing significant ear damage already.  Even fields planted to Herculex or SmartStax Bt corn that contain Cry1F are seeing greater amounts of damage than growers were expecting.  These Bt hybrids provide only approximately 70 to 80% control, so under heavier pressure, the damage can be significant.

Focus on later planted fields first.  Scout random areas of each field.  Look at 10 consecutive ears in a row.  You might see frass at the ear tip or a hole along the side of the husk where the larva entered. Peel back the husk and determine if larvae are present and make note of how extensive the feeding damage is.  Birds diving into fields is also a good indication that WBC is present and unfortunately they will also contribute to the ear damage.  Once the larvae reach the 6th and last instar, they drop to the soil and tunnel down deep to overwinter there.  If larvae are nowhere to be found in the field, it is a good indication that they have already started to get ready to overwinter.

Hopefully we experience a warm and reasonably dry fall to help mature the crop quickly and avoid ideal weather conditions that promote further ear rot development.

In dry beans, scouting 10 to 21 days after peak flight is the ideal time to determine if control is necessary.  Scout a field for 15 to 30 mins.  Select random plants in the field and take a good look at all of the pods on the plant.  If you can easily find pods with holes in them during that time, you need to spray.  If there is just surface feeding or scars on the pod, it may not be WBC damage. It could be from bean leaf beetles.  The only way to know for sure if it is western bean cutworm damage is if there are holes mining directly into the cavity of the pod.  Seed inside will also be fed on.  Open up the pod and see if anything is in there.  If you find a larvae, it is most likely European corn borer.  If nothing is in the pod, it is probably safe to blame the damage on WBC.  WBC larvae only feed at night in dry beans.  They drop out of the pods before sunrise and hang out in the soil or under crop debris during the day.  If in the time that you scout you are only finding a couple of pods with holes, it is not enough damage to warrant a spray.  But check again in another week to see if things have changed.  Matador and Coragen are both registered for dry beans.  Matador has a preharvest interval of 21 days.  Coragen has a preharvest interval of 1 day.

Pod feeding damage by WBC - Note the hole going into the pod

Surface feeding could be from other insects like bean leaf beetle

If a larva is present inside the pod during the day, it is more likely to be European corn borer

Counties that appear to have peaked last week: Essex, Chatham-Kent, Lambton, Oxford, Haldimand/Norfolk, Waterloo, Wellington, Brant, Dufferin, Grey, Simcoe, Kawartha Lakes, Hastings, Ottawa

Counties still seeing an increase in moth catches: Elgin and Huron (both experienced only slight increases), Middlesex, Bruce, Perth, York, Peel, Durham (saw significant increase), Prince Edward, Northumberland, Lennox & Addington.  Quebec locations in general are still increasing.

Our Northern locations can not be determined as we did not receive trap counts last week from these locations.

What are we seeing in the fields? Some decent sized larvae are being found in ears in some fields.  Some reps are surprised at the amount of damage they have found already despite not finding significant eggmasses earlier on.  Even in fields that have Cry1F.  My concern is that we still have a long way to go before harvest.  Ear rots may have time to set in because of the damage the larvae are making, exposing the ear to potential disease infection.  I strongly advice everyone to scout their fields in September to determine if it needs to be harvested earlier to avoid ear rot.

Dry Bean Fields -Now that some counties have peaked I suggest we all start focusing our attention at looking for pod feeding.  10 days to 21 days after peak flight is the appropriate time for management if required.  If you have to spend more than 1/2 hr to find just a few pods with feeding damage then that field is not worth spraying.  Check back again a week later.

I’ve also included an updated graph showing the counties that have been catching the highest average number moths per trap so far this year.  Counties with the Highest Trap Counts so Far

Many other counties are at risk too. Please make sure to visit the WBC Trap Network Website to see all of the trap catch maps for each region of the province.

Have a great weekend everyone!

So now what?  Well, this means we are still at risk of peak egg laying.  My crew has been running out to high trap count sites to look for eggs in fields but have not had much success outside of the original hot spot areas of Bothwell and south of Tillsonburg.  Does this mean that no other fields outside of these two areas have egg laying going on?  No.  It just means that the moths are more spread out now and scattered in ideal fields across the various counties catching moths in significant numbers.  We certainly can’t scout every field in the area of a trap site so it is up to you to be looking too.   Though the Bothwell and Tilsonburg locations were extreme with egg infestations ranging from 9 to 80% of the plants, other fields have got to be close to the 5% threshold too in other counties.  Scout late planted corn fields first that have not reached full pollen shed yet.  As long as you can feel a tassel in the whorl of the plant, the larvae can survive on it.  So target young fields first and move up from there.  Other host crops are also going to be at risk now as more corn fields starting to get beyond the more ideal egg laying stages.

Let us know too if you do find fields near or above threshold.  We want to make sure we document other locations of concern besides the heavy hot spots of Bothwell and Tillsonburg.  Even if it’s not until closer to harvest when damaged ears are spotted, we want to capture that information too.

Once we have all the data compiled from this week’s trap reports, I will make a graph comparing this year’s catch to the last two years just to show you how much higher our numbers are this year.  So..more to come tomorrow.