Soybean aphids are decreasing or stagnant in most soybean fields. You can see this in the final soybean aphid map (below) from the IPM scouting program.
Soybean Aphid Decline
Soybean aphids are decreasing or stagnant in most soybean fields. You can see this in the final soybean aphid map (below) from the IPM scouting program. Few fields are above the E.T. of an average of 250 aphids/plant. According to the USDA NASS, 98% of soybeans are setting pods (R6) and 19% are dropping leaves in North Dakota (USDA NASS News Release – August 24, 2015). It’s that time of year when reduced photoperiod and temperatures, and maturing soybeans triggers large numbers of winged soybean aphids to be produced. The reproduction of soybean aphid also changes to sexual reproduction where both winged female aphids and winged male aphids (for the first time this season) are produced on soybean. These winged aphids leave soybean fields and fly to their overwintering host, buckthorn, for mating. Mated females will deposit eggs near the base of buckthorn buds. The eggs overwinter and can survive very cold temperatures (-29 F). Winged soybean aphids are being observed in buckthorn in North Dakota and SW Minnesota (Source: B. Potter, SWROC).
Although most fields are below the economic threshold now (average of 250 aphids/plant, 80% incidence, and increasing populations), it is prudent to continue scouting any late-planted soybean fields, which could be at increased risk for soybean aphid colonization. Remember, populations must be increasing to justify any late season insecticide application. Please read, follow and understand the soybean insecticide labels which indicate that pre-harvest intervals are 21 days or longer.