Evidence for recruitment and retention of beneficial insects in grapes and hops using controlled-release dispensers of methyl salicylate (MeSA), a component of herbivore-induced volatile blends, is presented. In a replicated experiment conducted in a juice grape vineyard, sticky cards in blocks baited with MeSA captured significantly greater numbers of five species of predatory insects (Chrysopa nigricornis, Hemerobius sp., Deraeocoris brevis, Stethorus punctum picipes, Orius tristicolor) than unbaited blocks. Four insect families (Syrphidae, Braconidae, Empididae, Sarcophagidae) were also significantly more abundant in the MeSA-baited blocks, as indicated by sticky card captures. Canopy shake samples and sticky card monitoring conducted in a MeSA-baited, unsprayed hop yard indicated development and maintenance of a beneficial arthropod population that was nearly four times greater than that present in an unbaited reference yard. Four times as many S. punctum picipes and six times as many O. tristicolor were sampled in the MeSA yard. Similar contrasts in abundance of these predators and others were apparent when compared with levels recorded in the yard in previous years. The large population of predatory insects in the MeSA-baited hop yard was associated with a dramatic reduction in spider mite numbers, the major arthropod pest of hops, in late June, and subeconomic populations were maintained for the rest of the season. The evidence presented here is highly suggestive that the use of controlled-release MeSA in a crop could increase recruitment and residency of populations of certain beneficial insects. This strategy may have the potential to enhance the efficacy and reliability of conservation biological control in crop pest management.

The effect of imidacloprid on fecundity in twospotted spider mites, Tetranychus urticae Koch, was investigated in laboratory experiments using individual females on bean leaf discs. Mites were directly exposed to spray formulations of imidacloprid or fed on discs cut from a systemically treated bean plant. Imidacloprid-treated T. urticae produced 10-26% more eggs during the first 12 d of adult life and 19-23% more during adulthood compared with a water-only treatment. Increased egg production occurred immediately after exposure and lasted for about 15 d in sprayed mites. In mites exposed to imidacloprid by ingestion, increased egg production was not apparent until after 6 d and lasted until about day 18. Longevity was significantly greater in mites that ingested imidacloprid but not in sprayed mites. The significance and importance of imidacloprid-stimulation of fecundity in T. urticae to pest management in crop systems like hops, which routinely use this insecticide, is discussed.

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