Infested leaflet with approximately 40 aphids.
University of Minnesota entomologists have developed
a sampling plan, called "speed scouting." This plan
can greatly decrease scouting time in a field because every insect is not counted. The cut-off point is 40
aphids per plant. If a plant has less than 40 aphids. it is
considered to be non-infested. However, if the plant
has 40 or more (remember, counting additional aphids
is not necessary after 40). the plant is infested. Based
on the speed scouting sampling plan. three treatment
decisions are possible:
Speed scouting is NOT a new economic threshold! The economic threshold is 250 aphids/plant through pod set. Speed scouting is simply an alternative scouting method that considers whether a plant is infested or not. If there are more than 40 aphids, then the plant is infested. This sampling plan uses the percent infested pla nts as an indicator of damaging soybean aphid populations. Expect yield losses of up to 25 to 30 percent if a chemical treatment is not applied when the population is at 250 aphids/plant and increasing.
