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
