BLACK TWIG BORER
BLACK TWIG BORER, Xylosandrus compactus (Eichhoff), Curculionidae, tribe scolytini, COLEOPTERA
Black twig borers drill into the thin twigs of dogwood, grape, magnolia, live oak, laurel oak and many other plants from shade trees to orchids. Seemingly healthy plants are attacked. Infested twigs or stems will wilt and die back. An infestation is more severe for a young tree. In North Carolina, this pest is more common in the southeastern and coastal counties.
Black twig borers introduce a fungus, Fusarium solani, into the burrow that produces a white fungal "ambrosia" on which the grubs feed. The grubs apparently feed on the pith as well. Development takes 28-30 days from egg to adult during the growing season. Females begin laying eggs as the weather warms in Spring and will lay eggs until the weather cools in autumn. Grubs are most numerous during the growing season. This insect overwinters as an adult beetle inside the stems. After females emerge from a twig, they usually bore into the next twig within 30 minutes. The heaviest amount of beetle flight coincides with the time that dogwoods are flowering. Most emergence occurs from twigs between noon and 3:00pm.
Males are flightless and do not leave the brood cavity. (An unmated female produces only male offspring.) Females sometimes bore into plants without laying eggs. Only single females infest small twigs (< 5/16 inch) and such twigs usually die. Branches up to 7/8 inch may be infested with as many as 20 females. Such branches may die or form a canker around the infested area. Cankers may be as long as nine inches. Wilting symptoms usually appear just weeks after the first attack. Females tunnel into a twig for 3/4 to 1 1/4 inches to reach the pith or to form a small chamber where a loose cluster of eggs is deposited. The grubs feed on the ambrosia fungus cultured on the walls of the tunnels and brood chamber. Pupation and mating takes place in the infested twigs. New adults emerge through the entrance holes of the parent beetles. Adults overwinter inside infested twigs.
Pesticide (Trade Name)
permethrin (Astro [nonlandscape], PermethrinPro, others)
(*Home Defense, *Home & Garden Insect Killer, *Bug-B-Gone Multipurpose Insect Killer Ready Spray, others)
bifenthrin (TalstarOne, Talstar Lawn & Tree, Onyx)
*Suitable for homeowner use.
Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any, chemical. For assistance, contact an agent of the North Carolina Cooperative Extension Service in your county.
July 1994, J.R. Baker (Revised) Oct. 2001
Revised by: Stephen Bambara, Extension Entomologist, Sept., 2003
Web page last reviewed January, 2011 by the webperson.