Baute Bug Blog

It’s time to get out and scout for WBC damage in dry beans.  Based on trap counts we are now confident that some counties experienced peak flight the last week of July and others the first week of August.  Though I will admit that some trap sites are still catching lots of moths, especially the bean trap sites.  And the storm fronts that have pushed across the province over the last week have also been delivering some moths from Michigan.  One of our Grand Bend traps caught over 400 moths early this week, thanks to the same storm system that also hit Goderich.

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

Now that some of you have been fortunate enough to get some corn in, I am hearing reports and seeing tweets that soybean planting has also started.   If there was a year to protect your soybeans with an insecticide seed treatment it is this year.  Bean leaf beetles are going to be awfully hungry waiting for the soybean crop to emerge this year.  And given the significant snow cover this past winter, their overwintering success is expected to have been better than average.  When the adults first come out of their overwintering sites they look for the first soybean fields to emerge to feed on.  Until then they feed in alfalfa fields (though not an economic concern).  If the bulk of the soys get in around the same time and emerge at once, these beetles are going to have a lot of fields to pick and choose from.

Bean leaf beetle populations in Ontario has been generally declining.  This could be due to the introduction of Cruiser insecticide seed treatment that helps control this initial overwintering population.  Research being conducted through U of Guelph and OMAFRA is indicating that we only have one generation of adults per year in the summer.  That means, if we knock down the overwintering population in early spring, there are fewer adults to lay eggs and give rise to that first and only generation in the summer.  HOWEVER, this same survey work found that fields particularly in southern Bruce and northern Huron experienced on average much high adult populations over the last three years, with some fields reaching thresholds in late summer.  Growers in this region are encouraged to use Cruiser seed treatment to help reduce their risk of later season populations impacting seed quality from pod feeding.

Gaps in the stand are starting to show this week.  Aside from the typical culprits, moist soils can promote the less often accused.

Millipedes are typically a beneficial arthropod that breaks down crop debris and decaying plant material.  However, in the last few years, we’ve been seeing more direct feeding by them.  What is happening?  We have been planting earlier and earlier.  If the weather turns cool and wet, seeds that have sat in the ground for a bit, swell up but are slow to emerge, making for tasty treats for millipedes.  Corn is usually the target crop since it is the first to be planted but reports of soybean seed being fed on by millipedes have also come in this year.  Unfortunately insecticide seed treatments do not control them.  Warmer weather that helps get the crop up and out of the ground is really the only way to avoid this.

Slug feeding is evident this week.  This moist weather has brought them out of hiding.  Fields with decent amounts of crop debris harbour these pests, giving them a moist home to live in.  No till soybeans and spring canola are most at risk.  Though corn is also a host, it can usually grow out of the injury, as long as slug populations are not extreme. No insecticides are effective on slugs so this pest requires cultural control. Tillage is best, but for dedicated no tillers, using any device that can help to remove residue directly around the seed bed may reduce slug damage.  In some cases, it may be too late to take action this spring but make note of fields with slug problems and plan to take action this fall once the crop is off.

One additional note, bean leaf beetles have started to enter soybean fields.  In the fields I’ve been scouting, some plants were actually clipped off right at the base while trying to emerge.  Others had the classic round holes in the leaves.  Fields planted without Cruiser seed treatment should be scouted to ensure threshold is not reached.  16 beetles per foot of row during VC to V2 requires control or if clipping is found.

Thanks to Nick Zwambag for commenting on here that they are seeing cabbage seedpod weevil activity in winter canola near thamesville earlier this week.  But with this weather, little can be done about it and fortunately the cool temps should slow them down a bit.   Scout once this front goes through and see what infestations are like then.

Bean leaf beetles are not quite yet.  We’ve been sweeping in alfalfa fields and have not captured any.  We tend to see them emerging around this time so I expect if things warm up a bit, they will be making their way into alfalfa or newly emerging soybeans (if the soys escaped the frost).

These storms are also apt to be carrying in black cutworm and true armyworm moths.  States just to the south of us are reporting black cutworm flights and feeding activity.  Fields that had a decent weed mat this spring should be scouted.  There have been fewer armyworm reports but given the advanced wheat crop, those fields are going to look mighty appealing to the mother moths flying by.

And finally, Ohio is still reporting quite a lot of cereal leaf beetle activity, though I haven’t heard or found any yet here.  I do recommend that once this rain passes, we get out and look for armyworm and cereal leaf beetles.  This heavy moisture might be good for initiating entomopathogens but it needs to be a bit warmer for the fungus to get established.

Let’s hope we see the sunshine soon!

There are a few guys out there thinking that with the cooler nights, SOYBEAN APHIDS will be leaving their fields so they don’t need to spray those fields that recently reached threshold.  If aphids are staying at threshold levels 3 or 4 days after the initial assessment, you still need to spray.  Only those fields that are dropping in numbers or have reached into the R6 stage and are no where close to threshold can be considered safe from having to be sprayed for aphids.  The cool night temps do not guarantee the aphids will leave to look for buckthorn yet.  Triggers from plant quality may also determine whether they stay or go elsewhere.

HOWEVER other insects are starting to be a problem.  IP and seed fields need tending to still.  BEAN LEAF BEETLE adults are showing up in high numbers at a few of our sites in both Lambton and Elgin Counties.  Fields in other counties could also be at risk.  Scout fields to determine beetle presence and look at pods for feeding.  I like to pluck about 50 pods randomly in the field, grabbing pods from the top 3rd of the plant without taking the smallest/youngest ones.  If 10% of the pods collected (or in this case 5 pods) have feeding scars and holes on the surface, AND the beetles are still active in the field, a spray is required in IP or seed fields if the crop is not reached the middle of R6.  Preharvest intervals come into play if you get any deeper into the R6 stage of soys.  Look for clipped pods on the ground as well as this should also be included in your assessment.  If significant clipping is taking place and beetles are still active in the field, spray is required.

STINK BUGS  have also made an appearance at threshold levels in a field in Chatham Kent.  Very high numbers were reported by Joe Tomecek  and after some discussion it was obvious the field needed to be sprayed.  Again, only IP and seed soybean fields are at risk, as stink bugs impact quality by piercing the soybean pod, scaring the seed itself.  Control may be warranted in IP food grade and seed soybeans if an average of one stink bug per foot of row or 0.2 bugs per sweep are found during the late R5/early R6 stage of soybeans.