Plum Tree Borer Recovery: Merit Spray, Fertilization, and Insecticide Sources

A plum tree with borer history (bark splitting, gold sap) was treated with Bayer Advanced soil systemic. Owner can't eat fruit for 1 year per label. Half the tree looks good, half leafless. Asks about Merit spray for active borers and Japanese beetle control.

Assess Current Status

Scratch bark on leafless branches: green = alive (wait), brown = dead (prune). If no new borer signs (fresh sap, sawdust), the soil treatment may be working.

Active Borer Treatment

Merit (imidacloprid) trunk spray kills borers without entering fruit (unlike soil systemic). Available at tree nurseries/garden centers—not big-box stores. Ask for "imidacloprid 2% or 4% concentrate for trunk application."

Japanese Beetle Control on Plum

Homeowner options (check labels for plum registration):

• Carbaryl (Sevin)
• Permethrin
• Imidacloprid (foliar formulations)
• Neem oil (organic, moderate efficacy)

Apply at first beetle appearance; repeat per label. Merit trunk spray may provide some foliar uptake.

Ongoing Care

Fertilize with 10-10-10 at 1 lb/inch trunk diameter annually. Maintain vigor—borers attack stressed trees.