I have been receiving phone calls regarding fall armyworms moving into late planted soybeans. Most of these calls come after a producer has applied a Round up application to control grasses that may have been missed with previous applications. Fall armyworms moving off of these grass hosts are the “grass or rice strain” armyworms preferring grass hosts over legumes.
The problem is often exaggerated by the size of fall armyworm larvae moving off of grass into soybeans with large, late, instar worms causing severe foliage loss in a short time period. Many lepidopteran insects will consume more foliage in the last 3 to 4 days of development than throughout their entire life cycle as a caterpillar. This means that once the grass hosts have been removed by a herbicide application, soybeans can experience severe defoliation from migrating armyworms.
Thus, grassy fields should be scouted before an herbicide application is applied. If fall armyworms are found, a pyrethroid can be added to effectively control these insects before they move into beans.
If you have any questions or concerns please contact Sebe Brown or Dr. David Kerns for more information.
Sebe Brown Cell: 318-498-1283 Office: 318-435-2903
Dr. David Kerns Cell: 318-439-4844 Office: 318-435-2157