How to Manage Pests
UC Pest Management Guidelines
Scientific name: Scolytus rugulosus
(Reviewed 10/14, updated 10/14)
In this Guideline:
DESCRIPTION OF THE PEST
Shothole borers are tiny brown or black beetles. Their white legless grubs mine the sapwood of the tree and often reduce it to powder. Adult females bore tiny holes in the bark and lay eggs in the cambium layer of the tree. When the eggs hatch, young larvae feed and excavate secondary galleries at right angles to the egg gallery. The outline of the gallery system resembles a centipede. There are from one to three generations each year.
DAMAGE View photos of borer damage
Normally a number of shothole borer adults invade a tree at the same time. Healthy trees exude resin, which usually kills the insects. If the tree has injured or weakened areas, this increase in resin does not develop and the invasion is successful. Ultimately, larvae may girdle the tree, or tree part, and cause its death.
Spraying for this insect is not recommended. Shothole borers invade trees that have been previously damaged. The nature of this damage dictates the course of preventive action. To prevent attack by this beetle, maintain trees in a sound and vigorous condition, with sufficient fertilizers, water, and sunburn prevention to keep uninfested tree limbs from becoming damaged.
UC IPM Pest Management Guidelines:
Insects and Mites
W. W. Coates, UC Cooperative Extension, San Benito County
Acknowledgment for contributions to Insects and Mites:L. C. Hendricks, UC Cooperative Extension, Merced County