Grape Berry Moth: Appearance, Territory, Damage and Life Cycle

Latin Name: Endopiza Viteana

Appearance: Although the Japanese beetle is gradually approaching the top of the list in many regions of Maryland, the grape berry moth has traditionally been the most serious insect pest in the vineyard owing to direct and indirect damage to the berries and clusters.

The adult moth is a tiny moth with wingspan of around 3/8 inch. The front wings are dark with a little purple gleam to them. The head is brown, and the forewings may appear to have a black saddle-like band running across them in the center. Young larvae might be yellowish green or dull white in color, with a black head capsule. Mature larvae range in color from olive green to brown and are about 3/8 inch long.

Hosts Plants: Grape berry moths consume grapes, both produced and wild. They like cultivars with sensitive skin and tight fruit clusters.

Territory: GBM is endemic to eastern North America, where it thrives on wild and/or cultivated hosts and solely feeds on grapes.

Damage Insect Cause: Larvae feed on flowers and fruit, causing damage. When little fruit is injured, it becomes dark purple and falls from the stalks. Larger fruits are typically webbed into the cluster and shrivel or decay there. Third generation larvae eat inside berries before and after veraison. Berries can be hollowed out by feeding, and larvae can infect harvested fruit at this time. Grape berry moth damage after veraison predisposes berries to Botrytis and sour rots and attracts fruit flies, wasps, and ants.

Life History and Habits: In the eastern United States and Canada, this is the most common insect pest of grape berries. When vineyards are left unmanaged, grape berry moth larvae and bunch rot illnesses linked with fruit damage can kill up to 90% of the fruit. Infestations differ widely from vineyard to vineyard, year to year, and even within a vineyard. Vineyards in woodland regions, on the other hand, are particularly vulnerable. The adult is a mottled-brown moth with bluish-gray markings on the inner half of the front wings. When fully mature, the larvae of this tiny moth are lively, greenish to purple caterpillars approximately 3/8 inch long. Grape berry moths spend the winter in cocoons formed by folded leaves on the vineyard floor and in surrounding woodlots.

In the spring, overwintering adults emerge to mate, and females deposit eggs on or near flowers or berry clusters. In June, these eggs hatch and become the first generation of grape berry moths. The larvae of the first-generation feed on grape blossoms and immature fruit clusters and develop between mid-July and late August. These adults then emerge and mate, giving rise to the grape berry moth’s second generation. These ladies deposit their eggs on growing berries. The larvae eat internally after hatching until they reach maturity in August or September. The larvae of the second generation build cocoons in which they overwinter. A third generation occurs often in the pest’s southern distribution and on rare occasions in the northern tier of states.