Insects

Elm Leaf Beetles

Elm Leaf Beetles
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Both adults and larvae feed on leaf undersides, but the larvae-1/2 inch long, dull yellow grubs with black stripes-cause more damage. The 1/4 inch long adults are yellowish green, with a black stripe on each wing cover.

Target: Elms, Japanese zelkova.

Damage: Leaves are chewed to lace; injured leaves may turn brown and drop. Repeated defoliation may kill a tree. Weakened trees are also susceptible to elm bark beetles, which spread Dutch elm disease.

Life cycle: Adults overwinter in buildings and protected places. In spring, they fly to nearby elms to feed on unfolding leaves; they lay onion-shaped, yellowish eggs on the leaf undersides, then die. The larvae feed for several weeks, then crawl or drop down to the ground and pupate near the trunk base or in debris. There are up to five generations a year.

Notes: Destroy elm leaf litter. Apply sticky material on a 2 foot wide band on the trunk to kill larvae as they crawl down.