Shothole borer
Scolytus rugulosus
42 host plants
Last updated
Adult Scolytus rugulosus create shot-like holes in bark and wood of cherry and plum twigs and branches, with holes occurring in clusters; these are entrance or exit holes from brood chambers. Larval feeding between bark and wood girdles limbs and trunks, eventually killing affected growth. Most damage occurs on injured, stressed, or neglected trees rather than vigorous plants.
Keep trees healthy with proper pruning, irrigation, and balanced fertilization to enable sap and resin plugging of bore holes. Remove dead wood and prune infested branches. Dormant oil spray in early spring coats emerging beetles. Avoid late spring and summer pruning when beetles are active.
Quick Reference
Shothole borers are small (1/10" or less), brown to black, stubby-nosed beetles. Adults feed at the base of leaves or twigs. Later, they bore into the bark and lay eggs along a narrow gallery paralleling the grain of the wood. The white, legless grubs (bark beetles) feed by boring between the bark and sapwood, making narrow tunnels filled with sawdust-like frass (excrement). Feeding larvae can weaken or girdle trees. Larval galleries are typically at right angles to the first gallery, with the grubs pupate at the end of the galleries. The emerging adults leave tiny round "shotholes" in the bar
Cultural Controls
- -cultural control Severe infestations could indicate poor respiration of roots.
- A common cause of this is poor drainage or excess irrigation.
- The best management tool is to keep trees healthy with proper pruning, adequate but not excess water, and fertilizer.
- Healthy trees repel the beetles by plugging borer holes with sap and resins.
- Remove and destroy infested wood on the tree or piles of infested green wood nearby, especially cherry wood.
- Beetles also can attack young trees adjacent to piled...