Soybean aphids have been found in a number of locations in Ontario this year. Aphids were first found in Ontario in 2001. Since then, soybean aphids have been found in varying numbers across the province.  Management of this insect has also changed as the industry learns more about its behaviour.

Aphid populations are being found on untreated soybean seed in Ontario. Soybeans treated with Cruiser MaxxTM seed treatment have approximately 50 days of soybean aphid control. Soybean aphid populations either have overwintered in Ontario, or have been blown in by air currents from the United States. Infected areas usually start in pockets of a field. Once aphids become too crowded in a pocket, the next generation form wings and spread to new areas of the field.

When scouting for aphids, count the number of aphids on 10 random plants in 5 or more locations on a weekly basis. Note that aphid populations can fluctuate week to week. Once the soybeans initiate flowering, aphid populations of 250 aphids or more per plant on 80% of the plants in the field is the economic threshold. Once the economic threshold has been reached and populations are increasing, natural predators of aphids should be taken into consideration. The presence of lady beetles and aphid mummies on soybean leaves are the most obvious signs natural predators. An insecticide application too close to the economic threshold kills not only the aphid population, but natural predators as well. After an insecticide application, a resurgence of the aphid populations can occur more quickly than the natural predators. Insecticide applications are often a last resort to control this insect.

Aphid Advisor is an app for smartphones that helps determine the management actions required on a field by field basis. Users of the app enter the aphid and beneficial predator populations within a field and the result is a recommendation for management. Users can also monitor aphid populations on a regional basis to determine if overall aphid populations are increasing. The app is available at

Seed treatments and natural predators have provided additional tools to manage soybean aphids. These tools have been effective over the last few years and prevented increased insecticide applications. Aphids remain an economic threat to soybean production, and populations should be monitored weekly. If assistance is required to determine management strategies for your farm, do not hesitate to contact your agronomic advisor.

Shawn Winter, CCA-ON, Maizex Seeds Product Development Manager
Twitter: @SWinter_Maiz