There are generally two generations per year, although this may vary from one to three depending on temperatures. Adults overwinter in their galleries. Emerging adults fly with the warming of spring, peaking in mid to late April. The vines seem able to repel many of the attacks by copious sap flow from wounds, pushing out the invading beetles.
Adult females are about 2 mm long, brown, and
have truncate posterior ends; males are generally smaller. Males
are present as a relatively small proportion of the population
and never leave their native tunnels; hence they are seldom
collected. Tunnels are about 1 mm in diameter and are often
marked by sap running down the trunk. The economic importance of
ambrosia beetles in Virginia vineyards is not clear at this
time. Vines seem able to repel attacks in most cases, and
beetles will fail to establish. A further source of injury may
result from the propensity of certain pathogens, e.g., Agrobacterium
tumefaciens, the causal agent of crown gall,
to invade trunk wounds. The fungus inoculated by the beetles
as a food source for the larvae is not known to be pathogenic
to the host plant; however, other fungi, such as Fusarium spp., are
sometimes introduced accidentally.
Grape cane borer or apple twig borer (Amphicerus bicaudatus (Say), and Xylobiops basilaris (Say) (Coleoptera: Bostrichidae)
The grape cane borer, Amphicerus bicaudatus (Say), is a bostrichid beetle that feeds on a variety of trees, including apple, pear, peach, plum, forest and shade trees, and ornamental shrubs. It is also known as the apple twig borer. A related species, Xylobiops basilaris (Say), has been collected from Virginia vineyards, occasionally causing important injury to canes. This species is sometimes called the redshouldered bostrichid or redshouldered shothole borer. Note the downward projecting head in these BugGuide images (lateral; dorsal); this is typical of the family Bostrichidae.
The adult beetle is about 1 cm long, brown with a cylindrical body. The head is directed downward and a blunt abdomen bears a pair of horn-like projections. Adults overwinter in burrows in wood. They become active early in spring, boring into axils of grape and other plants. Eggs are deposited in May in dying wood. Neither young, vigorous wood nor old, dead, dry wood are suitable for larval development. Larvae develop during the summer and after a pupal stage adults appear in the fall.
The adult feeding is the source of injury to
grapes, since larvae feed in dying wood. Young shoots may
suddenly break off or die. Near the base of the injured section
is a small hole, with a burrow leading into the main stem. The
beetle may be found in this burrow. All new growth may be killed
in a severe infestation. Dying trees and prunings should be
removed from the vicinity of the vineyard. Trunk sprays of
bifenthin at the beginning of tunneling activity may help reduce