I have been out looking at some soybeans today and I am beginning to see some foliage feeders showing up in soybeans. Although, I have not seen ANY fields that were at a treatable level yet, growers should be aware that they are there and keep an eye on the populations as the season continues.
One of the most critical parts of controlling foliage feeders in soybeans is proper identification. Soybean Loopers are highly resistant to pyrethroid insecticides and growers will not get good control if they choose a pyrethroid to control them. Other foliage feeders can be controlled with a pyrethroid but many times growers are faced with a complex of foliage feeding insects, not just one species. The majority of insects that I have seen so far in Terrell County have been Soybean Loopers.
Below is a chart that shows the current treatment thresholds for foliage feeders in soybeans and a quick way to identify the common soybean foliage feeder insect pests. Growers need to keep both the insect thresholds and the defoliation thresholds in mind because when dealing with a complex of insect species as the defoliation threshold may be met before any of the individual insect thresholds are reached.
To properly identify each pests, growers should look at the number of abdominal prolegs (middle set of legs) of the insect. Soybean Loopers will have two pair of prolegs, Green cloverworms will have three pair, and velvetbean caterpillar and some others will have four pair of prolegs. The white arrows on the chart above show an example of which set of legs a growers should look at when trying to identify these pests.
Soybean looper is the most restrictive pest in terms of insecticide selection so here are the pages from the 2015 UGA Pest Management Handbook that recommends what insecticides be used for that species. If you need the recommendations for another species, the entire 2015 Pest Management Handbook can be found at http://www.caes.uga.edu/departments/ent/pest-management/.
If you have any questions, contact your local county agent for more information.