Baute Bug Blog

Many questions are starting to come in regarding WBC.  Just to help clarify what the action thresholds for western bean cutworm are, here is a quick summary:

In Corn: Scout 10 plants in a row in 10 areas of the field.  In non-Bt corn or transgenic corn that does not provide any protection against WBC (click here to see corn trait list and insects they control), if 5% of those plants have eggmasses on them, a spray is warranted.  Time the spray application for just after egg hatch when small larvae are present at the top of the plant.  Egg hatch occurs a day or two after the eggmasses turn purple (typically 5-7 days after being freshly laid).  For a list of products registered in corn, click here.  In these extreme temperatures, insecticides should be applied in the evening when temps are below 24 degrees C.  I’d recommend waiting to spray until after Thursday of this week when nighttime temps start to go back down to low 20s, high teens.

Is there a threshold for Cry1F corn yet?  No.  As you have read in past blogs and articles, Cry1F (eg. Herculex, SmartStax) only provides approx 70 to 80% control for WBC.  So you can experience some damage in heavy infestations. Eventually we may set a much higher threshold for Cry1F corn but for now, we don’t know what that is.  The research is taking place right now.  Populations would have to be very high to justify spraying Cry1F corn.  70 to 80% control is still better than not planting a Bt hybrid that protects against WBC.  The Agrisure Viptera Bt corn does provide excellent control (nearly 100%) of WBC will not need a potential higher egg threshold.

In Dry Beans: There currently are no thresholds established for dry beans yet.  However, research suggests that insecticide applications are most effective when targeted as soon as pod feeding can be easily found in the field (ie..if after a half hour of scouting you only find a few pods with feeding it is not worth spraying).  Pod feeding typically takes place 10 to 21 days after peak moth flight so having a trap at the field location helps determine when moth peak occurs.  Ontario has not yet reached peak moth flight this year.  To see a  list of products registered in dry beans, click here.  If a corn field directly adjacent to the dry bean field has reached threshold, then the dry bean field should be considered at risk.  Plan to scout that field for pod feeding and spray if warranted.

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.

There are a few fields in the Bothwell/Cairo area that are already above threshold for western bean cutworm.  The fields we are finding most of the eggs in are those that are the most advanced in growth stage for that area.   The fields we have found eggs in so far have all been transgenic corn fields that control WBC so spraying has not been necessary.  Though I know a lot of the fields in that area were planted with Herculex or SmartStax Bt corn (contains Cry1F), there may be some refuge, non-Bt fields or Cry 1Ab (eg. Yieldgard) fields out there that are at threshold and need to be sprayed.  Threshold is reached if 5% of the plants scouted have eggs.  Focus scouting efforts in fields that at least have a tassel developing inside the whorl as larvae won’t be able to develop on younger whorl stage corn.  Look at the top 3-4 leaves.  They tend to lay their eggs on leaves close to the whorl and always on the upper (hairy) surface of the leaf.

Don’t assume your field is at threshold and spray.  Please scout first for eggs since moths have just started to move into the area and if a field is sprayed prematurely when not at threshold, more moths may move in and lay more eggs in the next two weeks.  We are just at the start of the WBC season.  We have a long way to go yet as we have not come close to peak flight yet in the province.  Though traps in this area have been catching more than the rest of the province so far, the numbers have not been alarming.  My crew will be scouting fields in several counties over the next few weeks to see if we find any more hot spots.  Though Bothwell was one of our two major WBC hot spots last year, that doesn’t mean it will be the only one this year.  So if you find any fields in other counties that have a decent number of eggs, please let us know.

WBC Product information can be found at: http://www.omafra.gov.on.ca/english/crops/pub812/1wbc.htm

Scouting information and video was provided in a blog entry yesterday (was that really only yesterday..wow..what a summer!)

We are starting to see an increase in moth catches in our WBC trap network though we are still behind compared to last year.  Last year by this week we were catching 10 moths per trap.  We are not close to that yet.  However, things could change quickly.  Storm fronts can help bring in large masses of moths from other locations.  The big concern is that the corn crop is starting to approach the ideal growth stages for moths to lay their eggs in.  Moths prefer corn that is in the “pretassel” stages before the plant is fully tasseling and shedding pollen.  Much of the corn crop is approaching that pretassel stage now.  Larvae that hatch and try to develop on corn plants that are too young (ie. don’t have a tassel at least developing in the whorl yet) will die in a few days time.

So egg mass scouting should begin in fields that are more advanced in their area.  Also if you know of traps that are in the area that have been catching some moths, those are more apt to have some egg laying activity.  To help you scout for WBC eggs, here is the link to scouting video we developed last year http://bautebugblog.com/category/scouting-video/

Also, we are looking for fields with lots of eggs again this year so we can collect them to infest our research plots.  If you find fields that have a decent number of eggs, we’d be happy to take them out of your fields for you.  Here is a link to a pdf showing what the eggs look like and who to contact if you find some.  Wanted WBC Eggs

And finally, if you haven’t been checking out our weekly WBC trap maps yet, here is a link to them as well.  Ontario WBC Trap Network Maps.  You can find both the cumulative map as well as the weekly trap count map for each region.  A new addition is a map showing the range of corn growth stages for each county.  Thanks to all of the company reps who are sending us the growth stage data to map and thanks to Laresco for creating the map for us.  We have developed a special growth stage chart to help describe more of the  “pretassel” and “tasseling” stages of corn rather than just call it all VT.  Here is a link to the Detailed Corn Growth Stage Scale for WBC Observations.

Next blog on WBC will include thresholds and larvae and eggmass look a likes.

It’s time to start scouting soybeans to make sure soybean aphids are not reaching threshold.  A few fields that my crew has been monitoring have continued to rise in aphid numbers and are getting closer to threshold.  There are natural enemies present though and they could still win the battle.   We’ve seen some fields with lots of parasitized aphids (mummies) and lady beetles that have taken down most of the aphid colonies.  But this may not happen in every field.  Scouting on a regular basis will help you determine if the very important natural enemies can keep up or if the aphids win the war and reach threshold.

It’s been a while since some of you have had to spray your fields so I thought I’d remind you of the threshold.  The threshold is “250 aphids per plant and increasing on 80% of the plants during the R1 (first flower) to R5 (beginning seed) stages.”  This doesn’t mean that you need to spray as soon as you reach 250 per plant.  The actual injury level where the yield lost is equal to the cost of control is closer to 660 aphids per plant.  So between 250 and 660 you have a window of time to determine if the natural enemies will save you from spraying or not.  Remember, if you spray the fields prematurely, the natural enemies will take longer to build back up in numbers and the aphids will have essentially won with your help.  Only when the aphid populations continue to increase towards 660 per plant do you know for sure that the aphids are winning and that they need to be sprayed.

To help you identify the different natural enemies  that you may come across when scouting, here is a link to the Soybean Aphid Scouting Card – ENGLISH.  For chemical control options, refer to the Field Crop Protection Guide, OMAFRA Publication 812 at: http://www.omafra.gov.on.ca/english/crops/pub812/2aphid.htm

Big Exciting News – Keep an eye out for a smartphone app being developed by OMAFRA and U of Guelph that is due out in the next few weeks.   The “APHID ADVISOR” will be available on blackberries for this year (others to come in the next few years) and will help you decide whether you need to spray your field or not.  It stems from the dynamic action threshold work done by Rebecca Hallett et al. at the University of Guelph.  It takes into consideration the ratio of aphids to natural enemies you are finding and determine if there are enough natural enemies to not have to spray.  I will make an announcement here when the app is ready for use and will give you a bit more details about it then.

In the meantime, happy scouting on these nice summer days.