Nursery insect update
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
The barberry looper is a colorful caterpillar (yellow bands on sides and reddish-brown on top) with only two pairs of prolegs used to “loop” or “inch” their way when they move. This caterpillar may have two or more generations during the summer, so it can be found any time from June to September.
They feed exclusively on plants in two genera: Mahonia and Berberis. The young caterpillars may devour entire leaves. Barberry and other susceptible plants can be completely defoliated if larvae are abundant. Natural enemies usually keep the barberry looper under control, especially in landscape plantings, so it is rarely necessary to spray for them in the home landscape. However, when natural enemies are suppressed, as they sometimes are in nurseries, outbreaks may occur. Watch for caterpillar feeding damage to barberry and other susceptible plants during the summer and spray with Sevin, Decathlon, Astro or Talstar if injury levels become unacceptable.
European chafer grubs
If European chafer grubs were a problem in some fields last fall or this spring, consider treating those fields with Discus, Benefit, or Marathon or Flagship. A granular formulation is recommended for application to non-irrigated fields. These products will provide excellent grub control if applied before August 1. The only other alternative is to use Sevin, Discus or Flagship in the fall when grubs are found, but applications in the fall will not work as well.
Adult Japanese beetle
Tempo, Decathlon and Sevin are the most effective products for spraying adult Japanese beetle. The beetles will be actively flying around and feeding on preferred plants until early September. Be prepared to repeat spraying once per week or two if beetles are abundant. Sometimes it seems like the insecticides are not working because you still see new feeding damage after spraying. This happens because beetles may feed for a little while before becoming sick from the insecticide. With thousands of new beetles landing on plants each day, a little feeding from each one may result in some plant damage even though the insecticide is working.