Grape Cane Girdler, Ampeloglypter ampelopsis (Riley) (Coleoptera: Curculionidae)
The grape cane girdler is a small, black snout beetle about 1/8 inch in length. The insect strongly resembles the grape cane gallmaker. It overwinters as an adult underneath leaves and other trash in and around vineyards. Adult girdlers emerge during late May and early June.
When new grape shoots are 15 to 20 inches long and usually before bloom, the female beetle chews two series of holes around a shoot. These girdles are a few inches apart. The beetle then deposits a single egg in the girdle closest to the vine trunk. The larva that hatches from this egg feeds in the shoot pith between the girdles. Eventually, the shoot breaks and falls off at the outer girdle, leaving the infested section on the cane. The infested section of the shoot remains attached but may fall off later.
Larvae complete development during July and pupate within the shoots. The new adults exit from the shoot sections in August and overwinter. There is one generation of the grape cane girdler each year.
Economic loss due to the cane girdler ordinarily is not a major concern on mature vines. The girdles most often are made in a portion of the shoot beyond where the clusters are formed, so fruit loss is rare. However, where a concentration of girdled canes are observed in a vineyard, it is surely alarming and often causes undue concern. Nevertheless, injury may be important on newly planted or young Vines.
Removing infested shoots may be of some benefit as a control
procedure. Such affected shoots should be cut off below the lower girdle
before the beetles emerge in late July or August.
Current pesticide recommendations may be found HERE