Doug Pfeiffer, Fruit Entomologist at Virginia Tech has prepared a list of updates on grape insects that should be reviewed by all growers.
JAPANESE BEETLE:
As predicted, this is shaping up to be a year of high JB populations. This is a result of the rainy season last year. JB and related beetles have eggs with a low ability to retain moisture. Consequently, in drought years there is high mortality of eggs, with low populations of adults in the following season. In years with higher levels of soil moisture, we can expect higher natural survival of eggs and high populations of adults the next summer. Recall that vines can tolerate a considerable amount of foliar feeding before grape yield or quality are affected. Vines are most susceptible of JB feeding following veraison, when the berries become the sinks for photosynthates. JB adults concentrate their feeding in the top of the canopy and sprays can be focused there. This will limit the impact of sprays on beneficial species in the vineyard. Vines are very vulnerable when they are young, and young vines should be protected more rigorously. Some varieties (e.g. Norton) are more vulnerable than others, as well. Sevin, Imidan, Belay, Actara, Assail and Avaunt are recommended for JB control, also with the organic alternatives Surround and a combination of Neemix and Trilogy. The latter two are neem-based materials, are best applied before JB adults become established on the vines.
GRAPE TUMID GALL:
Grape tumid galls are cause by a species of cecidomyiid fly, grape tumid gallmaker, Janetiella brevicauda. In general, these are dark red, irregularly shaped galls – within the galls are tiny fly larvae, bright orange in color. There is a lot of variation in the gall development – on leaves, tendrils, petioles and rachis. It was once thought that these galls were caused by different midge species; they are now known to be caused by one species. Larvae overwinter, and flies begin to emerge in early to mid May. There are 1-3 generations per season. The first generation is probably the most important. Galls on foliage are of little importance, however, galls in the rachis can cause failure of the cluster. This season, a significant infestation of grape tumid gall has been seen in a Niagara block. Some varieties appear to be more sensitive than others; in the past, high infestation have been seen in Traminette. Historically this has been considered to be a minor problem in managed vineyards; in sensitive varieties, control may be needed. Movento (spirotetramat) is registered for this use. There is no sampling method for this species, and sprays should therefore be timed for the first appearance of galls in the spring. I would be interested in hearing about your experience if you find this insect in your vineyards. Images and further biological and control information are posted (and linked) in the Virginia Vineyard site (http://www.virginiafruit.ento.vt.edu/grapegalls.html).
YELLOWJACKETS:
Yellowjackets are usually late season pests of vineyard blocks, breaking berries, injury that may be falsely ascribed to honey bees, though bees are unable to break the skin of grape berries. Yellowjacket control is usually difficult. Insecticides are limited in their efficacy because choices are limited by preharvest intervals, and any insecticide will kill only the active field force of workers. Killed workers will soon be replaced by others. Several candidate insecticides are listed under fourth cover of the commercial vineyard pest management guide; this is linked in a page further describing yellowjackets in the Virginia Vineyard page (http://www.virginiafruit.ento.vt.edu/yellowjacket.html). Baits may be tried, especially early in the season, when overwintered queens are in the process of initiating nests. Many baits were developed that were more effective against western species of yellowjackets, and success was limited against eastern species. If the location of nests can be found, the nest can be destroyed using several insecticide preparations available for this use. The wasps are quieter at night, and this is the best time to try to control the nest.