October 11, 2014

1 - Elm leaf beetles are beginning to come into our houses looking for places to overwinter.

Yard and Garden October 11, 2014

Q.

I was hoping that you could help identify a bug that seems to be swarming the area, and getting into homes.

It is a green and black striped flying bug. It has two antennae, and what appear to be six yellow legs. It is 1/4 inch to less than a half inch long.

Many neighbors who have lived here a long time have never seen this bug before, and have complained about these bugs somehow finding the way into homes. I know of folks near other areas of town who have also had an infestation.

I have attached a photo (sorry it is not the best quality). Any insight that you could share with me would be greatly appreciated!

-Joe A.

Santa Fe

A.

Thank you for the picture. It helps identify the elm leaf beetle. This beetle and its earlier larval stage have been busy feed on the leaves of Siberian elm trees (often incorrectly called Chinese elms). Now that winter is approaching and night temperatures are falling, the beetles are looking for places to overwinter. Our homes seem to suit them just fine. They find their way into attics and into the voids between ceilings and flat roofs. Our light fixtures emit light into these areas, so they are attracted to the lights and enter our living spaces. You may see them finding their way into your living areas all winter, so be patient and persistent.

These beetles are not harmful to humans or homes. However, they are a big nuisance. They will often be attracted to light coming into windows where they accumulate. They often die near windows or on the window sills. This makes them easy to collect with a vacuum cleaner. Remember to empty the vacuum outside in the garbage, or take the filter outside. Do not just put the vacuum into a storage closet. The beetles will eventually find their way back into the house and into the closet. You may see them finding their way into your living areas all winter, so be patient and persistent. Indoor poison sprays are not needed nor are they recommended.

Next year those beetles that survive the winter will return to elm trees to lay their eggs as elm leaves begin to form, and begin the first of several generations of beetles in elm trees for next year. The adult beetles feed on leaves making holes in the leaves while the larval stages of this insect feed by skimming the epidermal layers from leaves, leaving brown skeletonize leaves. Early generations do little harm but as populations increase through the summer with subsequent generations, the elms may show significant foliar damage. Even so, these insects rarely kill the trees; they only cause them to look unattractive. Some people who consider the Siberian elm a weed or nuisance appreciate the elm leaf beetle as a "beneficial insect".

There are chemicals that may be used to control elm leaf beetle outdoors. Some may be applied to foliage of to kill insects feeding on the leaves; this includes some of the Bacillus thuringiensis strains labeled for killing beetle larvae (not the strain that kill caterpillars of moths and butterflies). Other chemicals may be applied as a wide band on the trunk below the bottom leaves. This treatment may kill the larvae as they migrate to the bottom of the tree to pupate and become adult beetles to lay eggs for the next generation.

A detailed source of information about elm leaf beetles is available from the Colorado State University Extension website.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!