The Economics of Aphids Infestations

"Soybean aphid populations remain small throughout most of Iowa except for the northeastern corner of the state. A few fields in Winneshiek County have reached the economic threshold of 250 plants and will soon be sprayed,” said Marlin Rice, Iowa State University (ISU) Extension entomologist.

Field scouting should occur weekly until plants reach the beginning seed stage (R5) or the field is sprayed. When aphids are found, estimate the population size per plant. Count all the aphids on several leaves and plant terminal to establish what 100 or 250 aphids look like and then use this as a mental reference for gauging populations on other plants.

Read the full story at
http://www.extension.iastate.edu/news/2005/jun/072801.htm