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| ELM
LEAF BEETLE Xanthogaleruca luteola (Muller) |
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| The elm leaf beetle is an introduced pest that feeds only on species of elm, Ulmus spp. Although all elm species are subject to attack, this species usually prefers Chinese elm, Ulmus parvifolia. Trees growing in landscapes are more heavily infested than those found in forests. | |
| Life History | |
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species overwinters as adults in houses, sheds, and in protected places
outdoors such as under loose bark of trees or house shingles. In late
spring adults leave their overwintering sites, fly to nearby elms, mate,
and begin laying eggs. Adults eat small, rough circular holes into the
expanding leaves.
Eggs are laid on end in groups of 5-25 on the underside of host plant foliage (Fig. 1). Each female may lay 400-800 eggs over her life span. Larvae feed on the lower leaf surface. Larvae feed for 3 weeks resulting in skeletonization of the foliage. The upper leaf surface and veins are left intact. At the end of the feeding period larvae migrate to lower parts of elm trees in cracks, crevices, or crotches on the trunk and larger limbs. It is in these protected places that pupation occurs, and adults emerge 7-14 days later during mid- to late summer. There is one complete generation and a partial second generation produced each year in Pennsylvania. |
Fig.
1. Life stages of the |
| Description | |
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| Eggs are orange-yellow and spindleshaped. Larvae are small, black, and grublike. At maturity larvae are approximately 13 mm long, dull yellow, and with what appears to be two black stripes down the back. Adults are about 6 mm long, yellowish to olive green with a black stripe along the outer edge of each front wing (Fig. 1) | |
| Damage | |
| Injury
caused by this pest may result in partial or complete defoliation of trees.
Heavily infested foliage will turn brown and often drops prematurely.
In some cases by mid-summer an entire tree may be defoliated. The majority
of damage is caused by larvae feeding on the lower leaf surface. Trees
that lose foliage as a result of heavy damage by this pest commonly produce
a new flush of growth that may be consumed by the remaining insects found
on the host tree. Hibernating adults in homes do not cause structural
damage but may be a nuisance.
Feeding damage by this key
pest seldom kills an elm tree. Severe defoliation may weaken a tree,
making it more susceptible to attack by other insects and diseases such
as Dutch elm disease. This pest does not carry Dutch elm disease, but
the smaller European elm bark beetle, Scolytus multistriatus,
and the native elm bark beetle, Hylurgopinus rufipes, that attack
weakened trees, do. Even without secondary attack by other insects and
diseases, repeated attacks by the elm leaf beetle may eventually weaken
trees to the point of death. |
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| Management | |
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Application
of a registered insecticide should be timed to impact early instar first
generation larvae and later the second generation larvae. Make the first
application according to label directions in late May or early June,
and a second application in late July or early August.
In the home: Adults seek winter hibernating sites in attics, garages, and other protected places in late summer and fall. In the spring they migrate back to their original host, elm trees. These beetles are a nuisance in the home, especially in the spring when they become active and are attempting to find their way out. However, they cause no damage. Most beetles can be kept
out of the home by screening or caulking voids or openings. Dead beetles
should be picked up with a vacuum cleaner to avoid subsequent infestations
of larder or dermestid beetles. |
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| Warning | |
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Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds. Authored by: Gregory A. Hoover, Sr. Extension Associate November 2001 ©
The Pennsylvania State University 2001
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