Soybean pests update
(Note: The following article is from K-State’s “Kansas Insect Newsletter,” August 25, 2016: http://entomology.k-state.edu/doc/extension-newsletters/2016/KSInsectNewsletter25.pdf – Steve Watson, Agronomy eUpdate Editor)
Green cloverworm larvae have been rapidly increasing all throughout the eastern two-thirds of Kansas. These worms are very well camouflaged and usually feed on the underside of leaves; thus, they are not always evident until holes start showing up in leaves.
Figure 1. Green cloverworm larva and feeding damage. Photos courtesy of Dept. of Entomology, K-State Research and Extension.
There has been concern about this leaf feeding, but generally an insecticide application may not be justified until the density reaches 10-12 larvae/ row ft. with about 30% defoliation, and larvae are still small (1/2 inch or less). However, in past years when those cloverworm densities have been achieved there has been an entomopathogenic fungus that rapidly decimates the populations.
This seems to be starting this year, as the first fungal-infected green cloverworm larvae were noticed on August 23 in several counties in Kansas. This fungus causes the green cloverworm larvae to stop feeding after 12-24 hours of infection and causes death 24-48 hours later. Sometimes, these infected larvae still look alive even in death, which is one of the characteristics of this fungus. There will probably be at least one more generation of green cloverworms to come.
Don’t forget to continue monitoring for adult bean leaf beetles, stink bugs, and podworms, all of which may feed on pods and/or seeds. There will probably be one more generation of podworms this year. For more information on soybean pests please see Soybean Insect Management 2016, available here: https://www.bookstore.ksre.ksu.edu/pubs/MF743.pdf
Jeff Whitworth, Extension Entomology
Holly Schwarting, Entomology Research Associate