By: Christelle Guédot, UW-Madison Department of Entomology

On 6/19/19 at the West Madison Research Station (WMARS) vineyard we did not observe any insect pest in significant number. Few grape flea beetle larvae were observed feeding on leaves but as mentioned in the last issue will not cause any economic damage on grape. As of 6/18/19, few grape flea beetle larvae, a few grape plume moth larvae, and some symptoms of grape tumid gallmaker were observed at the Peninsular Agricultural Research Station. None of these insects usually cause enough damage to warrant an insecticide application.

Grape plume moth (Figure 1) is a sporadic pest of grape in the Midwest and should only be managed in case of high pressure as some experienced back in June 2016. By fruit set, the larvae will have begun pupating and no more damage is expected. If you observe higher than usual pressure from grape plume moth and are still prior to fruit set, please refer to this article for more info.

Grape tumid gallmaker is also a sporadic insect that, as the name indicates, will trigger the plant to form a gall around it (Figure 2), and may cause damage to grape plants. Some reddish-purple blobs/spots from grape tumid gallmaker were observed on stems and leaves at the PARS vineyard. While grape tumid galls can reduce yield, especially if large numbers of flower clusters are affected as in Figure 2, they rarely cause enough damage to warrant an insecticide application. If your find grape tumid galls, prune out any damaged sections and destroy gall tissues before new gall midges emerge.

Thanks to Andi Nelson and Annie Deutsch for scouting at the research stations.

Happy growing season!

This article was posted in Grapes and tagged grape plume moth.