2017 Soybean Aphid Update

As soybeans enter into reproductive stages of growth, growers located across the northern Plains states into the upper Midwest and Great Lakes region (including the eastern Dakotas, Minnesota, northeast Nebraska, northern Iowa, Wisconsin, northern Illinois, and across lower Michigan into southern Ontario, Canada) are encouraged to begin scouting soybean fields for the presence of soybean aphids. Soybean aphids favor moderate temperatures and can double in population within a few days when environmental conditions are ideal (high temperatures in the 70s to low 80s Fahrenheit and no heavy rainfall events for several consecutive days). Once soybeans enter the reproductive growth stage, soybean aphid populations can threaten yield so diligent scouting is recommended. University thresholds state that a field with at least a 250 aphid/plant average population in at least 80% of the field and a growing aphid population may be a suitable candidate for treatment (University of Minnesota). With some fields already seeing soybean aphid populations near economic thresholds in the upper Midwest, it will be important to scout your own fields and not rely solely on regional extension newsletters or what your neighbors are telling you. Soybean aphid populations can vary considerably across a short distance. If you have a field near economic threshold, also monitor the weather forecast closely. If a several day period of above average temperatures and/or a heavy rainfall event is predicted, treatment may not be necessary in the short term. However, if a forecast of high temperatures in the 70s to mid 80s Fahrenheit and little/if any rainfall is predicted for the next several days, treatment should be considered based on established economic thresholds. Once soybeans enter the R6.5 growth stage, scouting and treatment will no longer be necessary as any potential yield loss will be minimal, if any.