Locust borer

You will see swollen, discolored bark patches or oozing sap on black locust trunks during late summer and fall. Larvae tunnel beneath bark, weakening the wood and making trees prone to wind breakage. Exit holes and yellow sawdust accumulate at the base. Black locusts are susceptible throughout the Puget Sound region, though the tree is not widely planted in Western Washington landscaping.

Remove affected branches below the mined area and burn them immediately. Maintain tree vigor through proper watering. For young or valuable trees, apply preventive bark sprays in late July targeting newly laid eggs. Parasitic wasps attack borers naturally. Stressed trees attract more borers, so prioritize cultural health measures.