Grape berry moth
Paralobesia viteana (Clemens)
Grape berry moth spends the winter as a pupa in leaf litter in and around vineyards. First generation adults emerge from the pupae before bloom. Male and female moths mate and then females lay circular, flat eggs directly onto the cluster around bloom. The eggs can be difficult to find because of their small size (approximately 1 mm diameter). Their shiny exterior can be used to detect them, especially with a hand lens. Eggs parasitized by wasp parasites turn black.
Larvae hatch from the eggs in 3 to 6 days, depending upon temperature, and feed on the cluster until they have developed to full size. Larvae of the first generation feed on young grape clusters and may remove sections of clusters. Then, when berries are formed, the young larvae burrow into the fruit. Webbing and larvae are visible in the small clusters during and after bloom. Damage from redbanded leafroller can be mistaken for grape berry moth at this time, so it is important to identify the larvae to determine the appropriate management strategy.
Grape berry moth is common in commercial and backyard vineyards in eastern North America. It is a native insect with wild grape as its historical host. There are two or more generations of larvae per year.
Larvae of the third generation feed inside berries before and after veraison. Berries may be hollowed out by feeding, and larvae at this time may contaminate harvested fruit. Damage by grape berry moth after veraison predisposes berries to infection by Botrytis and sour rots and can attract fruit flies, wasps and ants.
In Michigan, Pennsylvania, northern Ohio and New York, it is important to scout in mid- to late July for eggs and larvae. Detecting egg laying and egg hatch helps accurately time insecticide controls. In high-pressure vineyards, egg laying may continue over many weeks late in the season. Infestation is often greater on the border than the interior of vineyards, particularly near woods or hedgerows.
Regular cluster sampling in the vineyard interior and at the borders (particularly next to woods) can help to assess berry moth infestation levels and determine management needs.
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