Baute Bug Blog

It has been a few years for some since they have had to worry about soybean aphids, let alone make a spray decision.  So I want to cover off the key points you need to know through some of the repeat questions that have been coming in.  Anyone with more questions after reading this, please ask in the comment sections so we can all continue the discussion there.

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 am getting a lot of emails with photos from keen reps who think they have found Brown Marmorated Stink Bugs (BMSB).  I think it is awesome that everyone is taking this pest seriously and keeping an eye out for it in the fields but they are quickly learning that there are many other stink bugs that look very similar.  So far we have not found any BMSB in our traps or in our field surveys in Ontario this summer.  The only confirmed finding is still the one adult stink bug found in a home near Hamilton this spring.  Though I expect there to be more of them out there in Ontario in the next few years, until they start to increase in population, it is going to take some time for everyone to get used to identifying them from other stink bugs.

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

The 2011 season is clearly not like 2010.  We are not seeing a province wide WBC peak flight like last year.  Based on the trap counts that came in this week, it appears that some counties experienced peak moth flight last week (August 1st to 7th) while other counties are still going strong and may be peaking this week.  Though the general trend is that our Central and Eastern trap sites are still going strong, it is not fair to say that all counties in Southern Ontario peaked last week.  I can’t even draw a nice line on the map to show these differences.  So the best I can do is list the counties we know have peaked based on our data and which ones are still going strong.  Any counties missing from the list did not send in their data this week or last for us to be able to make a judgement call yet.

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.

Reports are coming in late last week of fields in Eastern Ontario reaching well above threshold levels for soybean aphids.  Just a few weeks prior, these fields had only 30 to 40 per plant.  I suspect other fields in even Central and Southern Ontario will also experience this kind of rapid increase as daytime and more importantly night time temps are now back down to a level that is more ideal for these aphids.  If not enough natural enemies are there to take them down, the aphids reach threshold quite quickly.

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….. 

As mentioned yesterday, last week trap catches shot up significantly.  I’ve included a graph to show just how big of a flight we are experiencing this year compared to previous years. Ontario 2009 2010 2011 Averages

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!