South Dakota Soybean Aphid Update

 

 

 

Soybean aphids have been observed in most parts of the state, however they are mostly present at very low populations. Last week several fields in the Southeast corner of South Dakota were reported to have soybean aphid populations that exceeded the 250 soybean aphid per plant threshold. After scouting a couple of these fields it was apparent that the soybean aphids would require management to reduce their populations. These fields were in an area where planting was delayed due to rain this spring. Many of the scouted soybean fields are at R5 (beginning seed: seed development in pods at the four uppermost nodes of the main stem) or R6 (full seed: seeds that fill the pod cavity are present in pods at the four uppermost nodes of the plant). However, some of the fields that were scouted in the southeast were only at the R4 growth stage (pods at the four uppermost nodes of the main stem are approximately 3/4 of an inch long).

 

 

It is important to continue scouting fields for soybean aphids up to the R6 growth stage. We don’t recommend applying insecticides for soybean aphid management after R6 is reached though, due to negliglible yield improvements. If you have a field that is near the threshold or surpassed it evaluate it for the presence of natural enemies.