WSJM July 27, 2005 Grape Berry Moth
Grape berry moth is a major pest of grapes in Michigan. It feeds only on grapes and usually has several generations a year. Infestations by grape berry moth can vary greatly from year to year and from vine to vine in a vineyard.
Grape berry moth has two summer generations. Right now, the moths of the second summer generation are starting to fly and will mate soon. The mated females then lay eggs directly on the grape clusters. This generation’s flight should peak in a couple of weeks. Adults will continue to emerge through September.
The eggs hatch into little larvae that tunnel directly into the fruit and feed inside the berry. Conspicuous red or purple spots develop on the berries at the point of entry. Larvae can and will feed on 7 or more berries in a cluster.
The grape berry moth tends to be more severe along the borders of vineyards, especially those next to wooded areas with wild grapes. Where grape berry moth is an annual problem, mid- and late summer sprays may be needed to control this pest. The decision to spray depends on the amount of infested berries a grower is willing to accept. Scouting of your vineyard is necessary to determine grape berry moth activity. Signs of larval feeding are easy to find on Concord, but more difficult on Niagara. Examine 100 fruit clusters for evidence of feeding. If you have more than 6 of the clusters showing some damage, a spray is needed. The Michigan Fruit Management Guide lists excellent control with Guthion, Imidan, Intrepid, Lannate, Capture, and Danitol. Only good control is obtained with Spintor, Sevin, Diazinon, and BT’s.
Now is the time to scout so that you don’t lose any grapes to grape berry moth.
That is all for today. This has been Al Gaus for Michigan State University Extension in Berrien County.