Gearing Up for Soybean
Aphids this Year

Reports of sightings of soybean aphids on soybeans have started to come in from fields across the Midwest US and Ontario and Quebec. Aphid numbers are very low but this does indicate that the aphid season has officially started. Though these sightings are a few weeks earlier than past years, it may be more of an indication that we are getting better at finding soybean aphids or that the crop was planted earlier this year and is up and available for the soybean aphids that are currently looking for their summer host. Regardless, it means that we need to be prepared for what this season could bring.

Unfortunately Ontario is challenged every year with the possibility of soybean aphids reaching threshold as we are geographically positioned to receive aphids from any location in the Midwest anytime in the season. Despite the US predicting it will be an aphid year based on the abundance of overwintering eggs they found last fall, what will truly determine if 2007 is a bad soybean aphid year is the weather conditions at the time that the aphids hit the field, the stage and condition of the crop when they do and whether the natural enemies present are up for the task of keeping the populations below threshold.

The threshold for soybean aphids is to "take action if populations are actively increasing above 250 aphids per plant on 80% of the plants from the R1 up to and including the R5 stage of soybeans". More aphids per plant are needed once the soybeans are in the R6 stage and once beyond the R6 stage, economic return from any insecticide application is not likely. Research from multiple locations across North America has shown this threshold to work well while helping to avoid misapplications of insecticide on the helpful natural enemies

We play an important role too. By scouting regularly, properly identifying the natural enemies of soybean aphids and determining if the soybean aphid populations are being kept below threshold by them is critical. To determine if the natural enemies are doing their job requires a minimum of two field visits to confirm if aphid populations are increasing above threshold or not. By scouting only once and making a management decision based on the aphid population you see at that one time puts you at risk of spraying and killing off a natural enemy population that was doing an effective job for you. Any aphids that survive the spray will then multiple potentially above threshold in the absence of their natural enemies thus resulting the need for a second application.

To help Ontario soybean growers stay informed of what is going on in fields across Ontario, OMAFRA and our scouting partners will be monitoring fields across the province again this year and will be reporting these results on both the Ontario Soybean Growers website (www.soybean.on.ca) and on the soybean aphid webpage of the USDA PIPE network (www.sbrusa.net).

Weekly scouting maps and current provincial recommendations, as shown below
(Figure1) from 2006 season, are posted to indicate when you need to start scouting in your own fields and determine what is going on.

Figure 1. Example of the weekly scouting map and Ontario commentary to be posted on teh USDA PIPE website

The Canadian Soybean Aphid Working Group involving experts from provincial governments, federal government, universities and industry has developed new reference material to use in the fields this year to help with natural enemy identification and soybean aphid management decisions.

Thanks to funding provided by the Ontario Soybean Growers, the Agricultural Adaptation Council, the Pesticide Risk Reduction Program of Agriculture and Agri-Food Canada, and Syngenta Crop Protection Canada, we will be providing you with the first installment of a series of soybean aphid reference materials this year. Be on the lookout this spring for "Soybean Aphid Scouting Cards" (Figure 2) and "Soybean Aphid Threshold Postcards" (Figures 3 and 4) available in Ontario, Quebec and Manitoba in both English and French.

Figures 2, 3, and 4: Introducing the "Soybean Aphid Scouting Card" and "Soybean Aphid Threshold Postcard" made available this season by the Canadian Soybean Aphid Working Group

And finally, for those interested in more of a hands-on lesson in how to scout for soybean aphids, identify their natural enemies and proper insecticide application, two sessions will be held at the SouthWest Crop Diagnostic Days being held at the University of Guelph, Ridgetown Campus on July 11th and 12th. More information about the event can be found on the website (link is below)

Happy Scouting!

Related Links

• Southwest Crop Diagnostic Day

• Ontario Soybean Growers

• USDA PIPE Network

| Top of Page |