Cutting soybeans for Forage? Consider some Insects!

Doug Johnson and Lee Townsend, Extension Entomologists.

Margined blister beete on soybean.

Some folks have been asking about cutting soybeans to be baled and used for forage. In general most insects in soybean are not a problem. However, blister beetles can be. Blister beetles are commonly found in soybeans thought not in large numbers. In my plots this year the black margined blister beetle has been the most common, though others will occur.

This insect and its close relatives the ash gray and striped blister beetles are infamous as a contaminant of alfalfa hay for their effect on animals, particularly horses. They are found in soybean for the same reason as alfalfa, they are attracted to and feed on blooming weeds.



While blister beetles will feed on soybean they are not considered an important pest in grain production. Nevertheless, because of their potential impact on animals, producers that intend to cut and bale soybeans for forage should be aware of their presence.

The simplest remedy for this problem is to cut the soybeans with a sickle bar, avoid driving over the downed beans and allow the downed beans to dry before bailing. Once the beans begin to dry out the blister beetles will fly away thereby removing any problem. The problem would come, as in alfalfa, with using a mower conditioner and / or running over the soybeans while they are still fresh. These actions could “crimp” the dead beetles onto the plants. This would result in the same problem as is faced when cutting alfalfa hay with a mower-conditioner.