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 Eucalyptus is a ubiquitous landscape,
shade, and windbreak tree throughout southern and central California. The trees are valued for their fast growth
and tolerance of poor soils and drought.
Eucalyptus is now threatened by several pest insects accidentally
introduced into California from Australia, one of which is the Australian gum
tree weevil.
Adults
are stout, red-brown beetles, ca/ 7-9 mm in length. Adults live 3-6 months,
with females typically laying 600-800 eggs during their lifetime. Eggs are laid inside dark-colored egg cases,
each containing 6-12 eggs. Egg cases
are attached to the upper surfaces of new foliage, where they are readily
visible as dark pellets. The larvae are legless, yellow-green, and slug-like,
with dark stripes down the sides. A
coating of slime and chains of black fecal pellets, which frequently adhere
to the larvae, characterize them.
The
weevil entered Ventura County, California in about the spring of 1994. The beetle has since spread throughout
Ventura and Los Angeles counties.Damage and Economic Impact: Both larval and
adult snout beetles consume eucalyptus foliage, particularly new shoots and
leaves. Adult feeding damage is
characterized by notching of the leaves, giving them a scalloped appearance. Young larvae score trenches in the leaf surfaces,
while older larvae consume the entire leaf.
Trees are rapidly defoliated by feeding weevils and can be killed by
repeated defoliation. Snout beetle
populations can build to high levels in a matter of months, so that entire
windbreaks and groves can be quickly stripped of foliage and eventually
killed. Area-wide control of the
snout beetle with insecticides is not feasible because of the problems
associated with pesticide coverage of large trees spread over significant
areas. Pesticide use is especially
problematic in residential areas.
REFERENCES:
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Cowles, R. S. & J. A. Downer. 1995.
Eucalyptus snout beetle detected in California. California Agriculture
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European and Mediterranean Plant
Protection Organization. 2017. Data sheets on quarantine pests: Gonipterus gibberus and Gonipterus scutellatus. Archived 2017-01-16 at the Wayback Machine.
Hanks, L. M., J. G. Millar, T. D. Paine, & C. D. Campbell.
2000. Classical Biological Control of the Australian Weevil
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Richardson, K. F. & R. H. Meakins. 1986. Inter-and
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