Fields scouted in the west central and south central also show increasing numbers from last week.
Bruce Potter, UMN Extension IPM Specialist, reports fields in those southern areas where populations are approaching treatable numbers that will likely be sprayed this week in southern MN. He adds that some fields have already been sprayed, not many but some. Additional reports for SW MN can be found at Southwest Minnesota IPM Stuff Newsletter prepared by Bruce. Subscribe or follow the link to read his updates.
We remind everyone to base treatment decisions on the threshold of 250 aphids per plant, 80% incidence and increasing populations. The unsettled weather Friday and Saturday across the region can produce some beneficial suppression of aphids, particularly if the rain events help trigger fungal infections that can kill the aphids.
The MN survey map illustrates where aphid numbers were assessed last week. Each pie chart represents a production field that was scouted. Fields are selected randomly. Scouts estimate populations on each plant sampled, placing a tally mark in the estimated # of aphid / plant range.The pie chart indicates the % plants observed within a range. Any pie charts that begin to show orange and red indicate those fields had plants with aphids into the 100's. The more red, the greater the percent plants with large infestations of aphids.This map was updated Sunday (7/23/17) and reflects fields scouted Monday through Saturday of last week.
Be sure to scout fields BEFORE making a treatment decision. Avoid the temptation to treat below threshold numbers because it is "cheap", or for convenience or ‘insurance’; this is bad management. Insecticide resistance means management will no longer be easy or cheap.
Before making any treatment decisions, be sure to read:
SOYBEAN APHID INFESTATIONS AND REPORTS OF FAILURES OF PYRETHROID INSECTICIDES TO CONTROL SOYBEAN APHID