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Biological Control Offers Control of Eucalyptus Pest

The Issue

The eucalyptus snout beetle, Gonipterus scutellatus, was discovered defoliating eucalyptus trees in Ventura County in March 1994. This insect has been introduced accidentally into several eucalyptus-growing regions around the world from Australia and has caused extensive damage wherever it has become established. Female beetles deposit hard brown egg capsules on shoots and young leaves. Both adults and larvae consume young and tender leaves, buds, and shoots. Extensive feeding completely defoliates trees and kills branches, while intermediate levels of defoliation retard growth and affect tree shape.

What Has ANR Done?

UC Riverside entomologists, including AES Professors Timothy Paine and Jocelyn Millar, responded rapidly to the invasion of this pest by introducing a specific parasitoid of snout beetle eggs, the wasp Anaphes nitens, as a natural biological control agent. The wasps were mass reared and released in Ventura County in 1994 and 1995, and they rapidly became permanently established.

The Payoff

Snout Beetle Population at Non-Damaging Levels

Snout beetle populations declined dramatically within less than a year. By 1997, snout beetle populations had dropped to barely detectable levels (Hanks, et al. 2000). Although reduced to non-damaging levels, the beetle has continued to expand into adjacent counties. However, in all cases, the parasitoid distribution has expanded in tandem, to mirror the distribution of its host. Consequently, where pesticide use has not disrupted the actions of the parasitoid, there have not been further reports of damage. The rapid implementation of a biological control program nipped a serious problem in the bud, providing an effective and permanent solution that requires no further input.


Supporting Unit: UCR Entomology Department

Dr. Tim Paine
Entomolgy 239
University of California
Riverside, CA 92521
(909) 787-5835 (Voice)
(909) 787-3086 (Fax)

Dr. Jocelyn Millar
Entomology 102
University of California
Riverside, CA 92521
(909) 787-5821 (Voice)
(909) 787-3086 (Fax)