A quick survey of soybeans around the northwest MN region revealed great
variability in
soybean aphid populations.
Some fields have not required treatment, many fields have been treated and are in good shape, other fields not treated may have quite variable numbers and often are related to growth stage with R3 fields still vulnerable to losses from threshold populations.
Reports from southwest MN and observations in the Detroit Lakes area have detected aphid movement to buckthorn. We can find winged migrants moving to buckthorn and producing nymphs at those sites. However, not all aphids are heading to
buckthorn. Quick estimates of populations on soybean suggest the aphids are only about 25% with wingpad development. Those without wing pads visible will be staying put; their babies will likely be winged, though.
Full maturity
and later planted soybeans, in
general , have the most aphids now and nymphs are still being
produced. Each field is
different!
Don't quit scouting too early. If you have questions on when
to stop using
the 250 aphid/plant threshold - see the video prepared by Bruce Potter, IPM Specialist, SWROC - Lamberton at the https://www.youtube.com/watch?v=VidX3KZEPnI.
He will mention growth stage information at
the end.
If you apply a pesticide to control insects or
mites, check
the field in 3-5 days to check performance.
Switch insecticide classes if you are re-treating any fields.
Unless accompanied by high winds, hail or a
flood, rainfall
events will not eliminate an aphid or spider mite problem. Prolonged cool, wet weather can produce
population crashing diseases affecting the aphids and mites. Heavy dews can be as
effective as rain in stimulating the fungal parasites that impact them.
