Environmental Entomology (1999) 28, 868-875

Diane M. Stark, Alexander H. Purcell and Nicholas J. Mills (1999)
Natural occurrence of Ametadoria misella (Diptera: Tachinidae) and the granulovirus of Harrisina brillians (Lepidoptera: Zygaenidae) in California
Environmental Entomology 28 (5), 868-875
Abstract: In southern California, populations of the western grapeleaf skeletonizer, Harrisina brillians Barnes and McDunnough, appear to be maintained at low levels of abundance by the combined activity of Harrisina brillians granulovirus (HbGV) and the parasitoid Ametadoria misella (Wulp). In contrast, outbreaks of H. brillians were common in central California in the late 1970s and 1980s. We investigated field populations of H. brillians in Fresno and nearby Madera Counties from 1992 to 1995 to determine the prevalence and impact of both natural enemies. A double antibody sandwich enzyme-linked immunosorbent assay (ELISA) employing polyclonal antibodies to HbGV was developed to detect virus in field samples. The sensitivity of the ELISA was ~10 ng of viral protein (equivalent to 100 ng/ml in the assay) detecting granulovirus in infected H. brillians larvae 72 h after infection. The ELISA did not cross react with the multicapsid nucleopolyhedrovirus Autographa californica MNPV at concentrations as high as 10⁵ ng/ml, but did cross react with another granulovirus Cydia pomonella GV at concentrations >10³ ng/ml. H. brillians pupae were collected from 4 vineyards. Both natural enemies were abundant at all sites, and the total mortality of host pupae ranged from 53 to 98%. Granulovirus accounted for as much as 97% mortality, whereas parasitism by A. misella ranged from 12 to 33% as estimated by marginal death rate analysis. These data indicate that both natural enemies cause significant mortality of H. brillians and that, contrary to earlier reports, A. misella is established in central California. Additionally, up to 47% of H. brillians adults eclosing from overwintering pupae tested positive for granulovirus by ELISA, indicating that host adults are an important mechanism of intergenerational and interseasonal persistence of the virus in host populations.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Alexander H. Purcell, Nicholas J. Mills

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
surveys/distribution/isolation
identification/taxonomy

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Harrisina metallica	Grapevine (Vitis)	U.S.A. (SW)
Betabaculovirus habrilliantis (entomopathogen)	Harrisina metallica	Grapevine (Vitis)	U.S.A. (SW)
Ametadoria misella (parasitoid)	Harrisina metallica	Grapevine (Vitis)	U.S.A. (SW)