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New Mexico State University

New Mexico State University

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Protect Elm Trees from Beetle Infestations With Early Treatments

LAS CRUCES -- New Mexico homeowners with elm trees in their yards should begin planning their attack now to control the dreaded elm leaf beetle, said a New Mexico State University entomologist.

"These pests overwintered in homes, garages, barns and abandoned equipment and are now making their way back to the trees," said Mike English, with NMSU's Cooperative Extension Service. "As they move into the trees, the beetles will lay clusters of 15 to 35 eggs on the undersides of the leaves. These eggs will hatch into small, black-headed larvae that will begin to defoliate the trees immediately."

Insect damage is evident in towns like Albuquerque with numerous elm trees. A large portion of the trees' leaves will turn brown by midsummer and will eventually drop. "Landscapes under the elm trees really become a nasty mess from the insects' fecal material and all the leaf shed," English said.

English recommends spraying every two weeks in late spring as long as egg clusters are evident. Injection systems that attach to the tree and distribute insecticide also are common, but most require that the installer has a pesticide applicator's license.

"Home owners have to be especially careful with the injection systems," he said. "The applicators are sharp and contain poisonous chemicals, so it's important to keep children and pets away from them."

For neighborhoods with numerous elm trees, a community-wide effort may be more successful than treating individual trees. "The insect numbers will just overwhelm you after a while if you have one tree and your neighbors have dozens," English said. "A control program covering several blocks is the best bet."

Indoors, elm leaf beetles can be treated with pesticides labeled for home use. "To remove the dead insects, vacuum and dispose of them," English said.