Plant Health Initiative

Soybean aphid insecticides

Asian lady beetles feeding on soybean aphids. Photo credit: University of Wisconsin

A single foliar-applied application of a labeled insecticide will effectively reduce aphid populations. The critical decision is if and when to treat.

When to treat

Use an action threshold (Economic Threshold) of 250 aphids per plant if populations are actively increasing. This action threshold should be based on an average of 250 aphids per plant over 20 to 30 plants sampled throughout the field. Regular field visits are required to determine if soybean aphid populations are increasing.

In university research across the upper midwest, treating below 250 aphids/plant resulted in no detectable yield increase. 250 aphids/plant is not where economic injury begins, rather it is the action threshold at which to treat and prevent the field from reaching the Economic Injury Level. In addition, early insecticide application will kill beneficial insects unnecessarily, allowing soybean aphid populations to rebound in a "natural enemy-free space".

Optimal treatment timing, and greatest economic return, result from treating soybean aphids at the Economic Threshold. This threshold has worked well in late vegetative (right at first bloom) to R5 soybeans. Spraying at or beyond R6 has not been documented to increase yield. This threshold incorporates an approximately 7-day lead time between scouting and treatment to make spray arrangements or handle weather delays.

Choosing an insecticide

Insecticides labeled and most commonly used for control of the soybean aphid
Product Name	Class	Company
Asana XL	pyrethroid	DuPont
Lorsban 4E	organophosphate	Dow AgroSciences
Mustang Max	pyrethroid	FMC Corporation
Penncap-M	organophosphate	Cerexagri, Inc.
Pounce 3.2EC	pyrethroid	FMC Corporation
Warrior	pyrethroid	Syngenta
Suppression:
Baythroid 2	pyrethroid	Bayer CropScience
Dimethoate	organophosphate

 

Refernce:Economic Threshold for Soybean Aphid, Journal of Economic Entomology 100: 1258-1276.