By Nick McGhee
Some soybean fields that I have been in recently have heavy foliage feeder pressure right now. I am seeing a mix of both Soybean Loopers and Velvetbean Caterpillars in most fields. Growers need to be scouting area soybean fields for foliage feeders now and be ready to make an insecticide application if a treatment threshold has been reached.
A previous post from a couple weeks ago discusses how to properly identify each foliage feeder pest and the treatment thresholds for each pest. It can be found at the following link: http://blog.extension.uga.edu/nochaway/2015/07/foliage-feeders-beginning-to-show-up-in-soybeans/
Many of the soybean fields that I have been in have a mix of both Soybean Loopers and Velvetbean Caterpillars. I have also seen some Green Cloverworms in some fields. While any treatment for Soybean Loopers should control both of these other species, growers have an opportunity to make a preventative insecticide treatment now to manage both Velvetbean Caterpillar and Green Cloverworm for the rest of the season.
Here is an excerpt from the 2015 Georgia Soybean Production Guide that discusses this preventative strategy:
Historical insect data indicate that the probability for treating late season foliage feeding caterpillars in soybeans is extremely high in the Coastal Plain Region of Georgia. Growers often budget 1-2 insecticide spray applications for late season insect control. Heavy populations of velvetbean caterpillar and soybean looper migrate into Georgia during August and September. For this reason, growers have been applying protective treatments using Dimilin in combination with boron at the R2-R3 stage.
Research with Dimilin and boron applied at the R2-R3 stage has consistently shown yield increases. A two ounce application of Dimilin at the R2-R3 stage controls velvetbean caterpillar and green cloverworm season long without disrupting beneficial insect populations. In most cases, fields treated with Dimilin at the R2 stage (full bloom) do not require an additional insecticide treatment for foliage feeders for the remainder of the growing season. However, soybean looper will sometimes require treatment and should be scouted closely. Fields that are not treated with Dimilin require an average of 1.5 treatments for late season insect control.
A couple of notes on using Dimilin now:
1) Most of the soybeans that I have visited were planted following wheat and are now in the R2-R3 growth stage that is appropriate for this application. Earlier planted, full-season soybeans are most likely beyond this growth stage and this application may no longer be needed.
2) This application will likely not provide acceptable control for Soybean Looper and should not be considered as a management tactic for this pest.