The Black Twig Borer Poses a Threat in East Texas Trees

The black twig borer, with the scientific name Xylosandrus compactus, is a tiny ambrosia beetle barely 1/16 inch long. It bores into the thin twigs of over 220 trees and shrubs, including southern magnolia, grape, sweetgum, pecan, dogwood, water oak, red maple, redbud, grape and many other plants. Seemingly healthy trees are attacked. The first evidence of an infestation is a condition known as “flagging,” where scattered twigs throughout the tree’s crown wilt and die (see link). Close examination of the dead twigs will reveal minute, circular holes (1/32 inch in diameter), usually on the underside of the dead twig. The adult beetles introduce a fungus which causes a black staining of the sapwood. Females begin laying eggs within the infested twig from spring through fall. The larvae or grubs hatching from the eggs feed on the white fungal “ambrosia” and also on the pith (center) of the twig. Pupation and mating of brood adults occurs within the infested twigs. The insects overwinter as adults, emerging through the entrance holes of the parent beetles and attacking trees most commonly in the spring when dogwoods bloom. Click here for more information