Update on Soybean Aphid By Wayne Bailey

Soybean aphid can be a problem early in the spring as overwintering eggs hatch on buckthorn (Rhamnus) and winged soybean aphids move to soybean fields. Aphids produced during early spring are usually not a problem in Missouri, although this year an infestation was found in Nodaway County in NW Missouri. Infestations were light with most aphids possessing wings suggesting they recently migrated from buckthorn to the soybean fields. Young aphids born from the winged form of the soybean aphid are usually non-winged and may colonize soybean plants if conditions are suitable. Of much greater concern is the potential for late July migrations of soybean aphids into Missouri from more northern states. At present, entomologist from Canada, Wisconsin, Minnesota, Michigan, Ohio and New York are reporting moderate infestations of soybean aphids on seedling soybean. Numbers range up to 50+ aphids per seedling plant in some areas of these northern regions. If these populations continue to grow as expected in these areas, then the potential for heavy migrations of the aphid into Missouri during the 3rd and 4th weeks of July is increased. Field conditions, weather patterns, and beneficial insect populations will all influence aphid population growth and help determine whether Missouri will receive aphid migrants during July. We will continue to monitor aphid reports from states in the north central region of the U.S. and provide early warning as to whether the aphid will be a problem in Missouri during the 2005 growing season.

Wayne Bailey
573-882-2838 office or
573-864-9905 cell