The 2005 ESA Annual Meeting and Exhibition
December 15-18, 2005
Ft. Lauderdale, FL

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Friday, December 16, 2005 - 3:30 PM

Crambine web worm larvae attacked by Beauvaria spp. in wheat and grass seed

David Bragg,, Washington State University, Entomology, P O Box 190, Pomeroy, WA

A complex of insect larvae feeding on the crowns and roots of wheat resulted in 40% stand loss. Pyralid moth larvae of the Genus Crambus, Crambus agitatellus Clemens (grass web worm), and Crambus vulgivagellus Clemens (vagabond webworm) were the primary pests. A significant number of maturing larvae of the Army Cutworm, Euxoa auxiliaris Grote, a common and serious pest of winter wheat were also present, along with wireworm larvae. Any one of these four pests in the numbers present by each species could account for serious damage to the wheat stand. There were more larvae in the lighter soils moving up slope in the wheat. Blue Grass Webworm, Crambus teterellus (Zinken), was found in an adjacent grass seed field under droughty conditions. This moth has pink tinged larvae smaller that the Vagabond Crambus which has grey spotted larvae. All Crambine moths lay eggs after adult emergence post harvest. The 1st instar larvae feed on the crowns for a time then over winter as larvae which begin feeding in the early spring, pupating as the crop matures. There is one generation per year for most webworms. Many Lepidoptera larvae in wheat and Blue Grass fields sampled showed an entomophagus fungus, apparently Beauvaria spp., which covered larvae with white cottony fuzz. All webworm larvae reared for adult ID died of this pathogen prior to pupation. This fungus may have value as a potential biological control for webworms and cutworms.

Species 1: Lepidoptera Crambidae Crambus agitatellus (Grass webworm)
Species 2: Lepidoptera Crambidae Crambus vulgivagellus (Vagabond webworm)
Species 3: Lepidoptera Crambidae Crambus teterrellus (Blue Grass webworm)
Keywords: wheat, worms

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