We have heard a few reports of either bean leaf beetles or grasshoppers increasing in soybeans. As we start to approach the end of the growing season the larger concern with these insects is the potential for pod feeding, rather than foliage feeding. Pod feeding directly impacts grain quality.
Crop stage is also an important consideration. Late-planted fields or double-cropped soybeans which are still green when other fields are drying down can be “trap crops,” attracting both bean leaf beetles or grasshoppers leaving the other fields. Such fields bear close watching.
Evaluation of pod injury should be based on inspection of all pods on 10 randomly selected plants. Be sure to sample at least 100’ into the field to avoid making your entire decision based on field edges, where damage can be worse than in the field as a whole.
On each plant sampled, count the number of total pods and the number of pods exhibiting pod injury, and then determine the percent pod injury based on the 10 plants inspected. It is important to estimate percent pod injury on inspection of the entire plant.
Treatment is justified if the percent pod injury approaches 10 to 15%, and beetle adults or grasshoppers are still present and active in the field.
When making a treatment decision, also consider the pre-harvest interval of the insecticide you’re considering – which can be an important consideration at the end of the season as harvest approaches. For more information visit our factsheet here.