Soybean aphid populations continue to increase in NW Minnesota. Below is a summary of scouting reports from July 17 to 22. The map reflects increasing numbers and treatment decisions in the NW region.
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.
Sunday, July 23, 2017
FRIDAY, JULY 21, 2017
Robert Koch (Extension Entomologist), Ian MacRae (Extension Entomologist), Bruce Potter (Extension IPM Specialist), and Phil Glogoza (Extension Educator – Crops)
By now you should be scouting your soybean fields for soybean aphid on a regular basis. Soybean aphid can be found in most fields throughout the state and populations have reached economic threshold (250 aphids per plant) in some fields in northwest Minnesota and have require insecticide application to protect soybean yield. In northwest Minnesota (especially around Norman County), applications of pyrethroid insecticides are failing to adequately control aphid populations in some, but not all, fields.
This is the third year in a row that we have received reports of failures of pyrethroids to control soybean aphid in Minnesota. In 2015 and 2016, field-level failures of pyrethroid insecticides were reported (Figure 1) and pyrethroid resistant populations of soybean aphid were confirmed in Minnesota, particularly in parts of southwest Minnesota. In addition, a resistant aphid population was also found near Crookston in northwest Minnesota in 2016, just north of the area experiencing problems this year.