The elm leaf beetle is just one of many damaging non-native insect pest species that feeds on trees in the northeast US, though this species has established an invasive population throughout the country. Just as this species’ common name suggests, it feeds only on a variety of elm tree species, particularly the Chinese elm. Unlike most invasive tree pest species in the northeast, the elm leaf beetle inflicts more damage to landscaping elms located on residential and urban properties than it does to wild elms located in forested areas. During the summer, elm leaf beetles strip landscaping elms of their foliage, but during the fall, these pests become significant nuisance pests within homes.
Similar to other invasive true bug pests, like brown marmorated stink bugs and Asian lady beetles, elm leaf beetles invade homes in large numbers during the fall in an effort to safely overwinter until the arrival of the spring season. Elm leaf beetles may overwinter in the natural environment beneath tree bark or under loose plant matter, but every fall, these pests congregate on the exterior walls and the roofs of homes where they settle in narrow cracks and crevices. For example, these beetles harmlessly overwinter beneath roof shingles and behind siding, but a large number also gain access indoors where they congregate in hard-to-access areas, most notably in wall voids.
Once elm leaf beetles secure shelter within an obscure indoor area, they enter into a semi-dormant state known as “diapause.” While in this state, elm leaf beetles, and many other insect species that enter diapause, do not feed or reproduce. Elm leaf beetles can remain indoors during the entire winter season before emerging from wall voids during the spring in an effort to re-enter the natural environment. On unseasonably warm winter days, elm leaf beetles regain activity and swarm toward windows in an attempt to fly outdoors. These mid-winter indoor swarms are both a nuisance and a surprise to affected homeowners who do not expect airborne insect pest activity within their home during the winter.
Preventing elm leaf beetle invasions during the fall involves sealing cracks, crevices, utility openings and other entry points on a home’s exterior. Properties that see a high degree of elm leaf beetle activity during the summer are likely to see nuisance invasions come fall. In these cases, professional-grade insecticides can be applied liberally within yards in order to minimize elm leaf beetle nuisance issues in homes come fall.
Have you experienced nuisance issues with elm leaf beetles in your home?