A little bit about Cara: She is currently completing her thesis on the bean leaf beetle in soybeans for a Master of Science in Environmental Biology degree at the University of Guelph.   She has a Bachelor of Commerce degree from University of Windsor and an Associate diploma in Horticulture from University of Guelph, Ridgetown Campus.  Before joining OMAFRA, Cara ran her own business and was involved with several agricultural research projects through the University of Guelph, including the Soybean Breeding Program and the Soybean Aphid Project.

Cara will continue this blog in my absense so no need to stop visiting the blog over the next year.  There are always pest issues to talk about.  And she might even line up some guest bloggers..i.e. top field crop entomologists from both sides of the border to discuss insect topics that they are experts in.  You can reach Cara through this blog, by phone at my office and cell numbers or you can email her at cara.mccreary@ontario.ca.

I am sure you all will make her feel welcome and keep her on her toes with all of your insect issues over the next year.  I know I am leaving you guys in good hands.

I wish you all a great harvest season and I will see you in a year from now.

Tracey

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

Q1.  With soybeans at $15, does that threshold change?  Answer:  No. The economic threshold of “250 aphids per plant and increasing on 80% of the plants in the field during R1-R5″, already takes into consideration a wide range of soybean prices.  The actual economic injury level (where the cost of control is equal to the damage they are causing) is around 660 aphids per plant.  So you have a large buffer area between the threshold and the economic injury level to determine if a spray is needed.

Q2.  Isn’t it getting late to spray for aphids?  Answer:  No. Soybeans are susceptible to aphid injury from R1 (first bloom) all the way until your crop reaches R6 (Full Seed – when the pods at the top of the plant have seeds filling the cavity of the pod).  Once it is in the R6 stage, you need a lot more aphids (over 1000/plant) to see any yield response.  And you need to be cautious as you approach R6 as you are also close to approaching the pre-harvest interval aka days to harvest limit for the products registered   But much of the soybean crop still has a ways to go before reaching R6 so please keep scouting.

Q3.  I have a field that has been fluctuating from 100 to 400/plant and back down over the last few weeks.  Do I need to spray?  Answer:  Most likely not -but keep watching. The fact that the aphid populations keep fluctuating in this fields is a good thing.  It indicates that the natural enemies are helping.  Plus the cooler night temps are not as ideal for the aphids so their development is going to slow down a bit, allowing for the natural enemies to keep up.  If the crop is not stressed (i.e.  it has been getting a decent amount of rain and is lush) you can hold off to closer to the ECONOMIC INJURY LEVEL before you need to spray.  So only if you see these fields hitting 500 or more and are staying at that level might it still be worth spraying.  Again, make sure the crop hasn’t reached R6 yet.  Any fields that are really stressed from lack of moisture (and I know there are some out there) need to stay closer to the 250 threshold and increasing  (but not below that number).  If populations keep fluctuating from 100 to 300 and back down, even these fields may not need to be sprayed.  As long as populations fluctuate, it is a sign that the aphids aren’t getting the upper hand.

Q4.  I am seeing 150 aphids per plant.  Should I get out and spray now and get ahead of them?  Answer:  Absolutely NOT. The threshold of 250 per plant and increasing is there for a reason.  You are not losing yield equivalent to the cost of the spray until closer to the 660 aphids per plant.  At 250 aphids per plant and below, there is a lot of opportunity for natural enemies to keep up with the aphid populations and provide you with free biological control.  If you spray too early, you kill these natural enemies off and give the aphids the freedom they need to build up more rapidly.  You will never get 99% control of the aphids but you are likely to get that good of control of the natural enemies.  Even if 10% of the aphids survived a spray, they will easily build up again in the absence of their enemies.

Q5.  I saw a Speed Scouting Aphid App recently launched out of the US.  Is it something we should use here?  Answer:  Unfortunately No. Nothing against my US counterparts who developed this concept.  But when we tested it here in Ontario in many field scenarios, when the aphid populations were building up rapidly, it did not tell us to spray soon enough and when the populations were building up very slowly, it often told us to spray when we didn’t need to.  So I don’t recommend its use in Ontario.  What I will recommend is the aphid app that we are developing here in Ontario (between UofG and OMAFRA).  I am not being biased here.  It is called the Aphid Advisor.  We are in the final testing phase this week.  Currently it is only for blackberries but if it is successful, we will be working on getting it for the other smartphones in use.  It does still require you to do the full plant counts on 10 random plants in the field but it also has you punch in the number of natural enemies hanging out on those plants.  Based on the forecast for your area (determined by the location you enter) and the ratio of aphids to natural enemies you are seeing, the app will tell you if you need to 1) Spray, 2) Wait and Watch or 3) Don’t spray.  It is based on the dynamic action threshold work that Rebecca Hallett et. al. did the last few years at U of G. We tested it in the field and it really does help to determine if the aphids are going to win the battle over what natural enemy population exists in that field.  It takes care of that grey area between the 250 to 500 aphids per plant range where you are uncertain as to whether you need to spray or not.  So keep an eye out for that launch expected in just a matter of days.  And we will be on display at the OMAFRA/OSCIA tent at the Outdoor Farm Show for all to try out.

If you want any more information on soybean aphids, here are a few helpful links:

Agronomy Guide for Field Crops – Soybean aphids: http://www.omafra.gov.on.ca/english/crops/pub811/13soybean.htm#soybean

Field Crop Protection Guide – Soybean aphids control options: http://www.omafra.gov.on.ca/english/crops/pub812/2aphid.htm

Soybean Aphid Scouting Cards:   English  http://bautebugblog.com/wp-content/Soybean-Aphid-Scouting-Card-ENGLISH.pdf French  Soybean Aphid Scouting Card – FRENCH

I’ve put together some slides to compare the look a likes to help you out in the field.   Any tiny first instars can not be identified by a photo and need to be sent in to me or my colleague Hannah Fraser (OMAFRA-Vineland) for ID.  If you think  you have BMSB, please contact us.

Click on the images below to view them in a larger format.

For more information on Brown Marmorated Stink Bug visit the OMAFRA BMSB webpage at: http://www.ontario.ca/stinkbug

Scouting soybeans at least once a week from now until fields are into the R6 stage is advised.  Particularly since other pests are also active in the fields now including spider mites, defoliators like Japanese beetles, red-headed flea beetles and bean leaf beetle which the latter are also starting to feed on the pods and clip some pods off plants in some fields.

Besides…aren’t soybeans a lot easier to scout than corn fields this time of year?  Just saying…..