Evoxysoma vitis

Vitis

Fruit and bud galls
Shriveled berries and enlarged seeds

Evoxysoma vitis Saunders

The seeds of the wild grape in the eastern United States and Canada are commonly infested by a milk-white larva about 1/8 of an inch in length which eats out the kernel. The insect passes the winter as a larva within the seed. Pupation takes place in June, and in early July the adult gnaws its way out of the seed, leaving a small, round hole. The adult is a small four-winged fly about 1/8 inch in length and black in color. The female is provided with a sharp needle-like ovipositor which she inserts through the skin and pulp of the grape and deposits her minute whitish egg in the kernel of the seed. Most of the egg-laying takes place in July. Cultivated varieties are rarely infested, but we have occasionally seen Delawares badly injured by the punctures made by the female in ovipositing. The injured berries color prematurely and sometimes shrivel and drop. Infestation by the grape-seed chalcis may be prevented by destroying all wild grape-vines in the vicinity of the vine- yard, and by not allowing any of the infested fruit to remain in the vineyard after picking time.

Evoxysoma vitis Saund.

Vitis
Fruit and Bud Galls
Shriveled berries and enlarged seed, summer

Evoxysoma vitis

There are two species of grape seed chalcid. Prodecatoma cooki is widespread but rare within its geographic range, with reports from Canada to Venezuela. There is no mention of Evoxysoma vitis in the scientific literature since 1924. It has disappeared.

Grape seed chalcid was found damaging ‘Concord’ grapes, Vitis labrusca and Virginia creeper, Parthenocissus quinquefolia in a back yard home garden setting in Montrose, Colorado (Montrose County) in 2011.

A search of literature published on grape seed chalcid reveals two species of seed chalcids that attack grapes. Evoxysoma vitis (Saunders) was originally described in Saunders 1869, with life history observations in Crosby 1909a & b. Crosby 1909a describes a second species of seed infesting chalcid, Prodecatoma phytophaga, from Virginia creeper. Gahan (1924) recorded the first account of P. phytophaga feeding on grapes. He recognized that there were actually two distinct species of chalcid that fed on vitaceae seeds. His mention of E. vitis is the last mention of this insect in non-taxonomic scientific publications. He recognized synonymy of P. phytophaga and Decatomidea cooki (Howard) in his 1951 publication and renamed the species to Prodecatoma cooki (Howard). Adlert documents P. cooki in Florida grapes in two 1973 publications. It has been reported from Canada, several US states, Venezuela (Cermeli 1973) and Mexico (Cortez-Madrigal et al. 2012).