How to Control Lilac Borers
Lilac borers, also known as ash borers, produce larvae that burrow into the stems of lilac and ash trees. They overwinter there, feeding on the plant material and eventually breaking out of the branch by boring holes through the stems. This damage is fatal to a lilac plant, and without proper control a gardener will have to destroy the plant to prevent spreading of the borer. Does this Spark an idea?
Instructions
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Use garden shears to cut out any heavily infested branches. Burn the branches to prevent the spread of the borers. Do this in the fall or winter.
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Set out lilac borer pheromone traps around the trees in April or May, according to the package directions. The traps will capture any males present in the tree and prevent production of more larvae.
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Apply a borer insecticide to the entire main trunk of the tree 10 days after you catch the first borers in the pheromone traps, following the directions on the package for dilution, if necessary. The most effective borer insecticides contain permethrin. Repeat the application six weeks later.
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Tips & Warnings
Avoid using mechanical lawn equipment around the base of the trees. Lawn mowers and edgers can cause trunk damage, giving borers easy access to the tree.
