Abundance and phenology of mites, leafhoppers, and thrips on pesticide-treated and untreated wine grapes in southcentral Washington

摘要

The abundance and phenology of mites, leafhoppers, and thrips were monitored monthly (May-October) during 1999-2000 in three pairs of pesticide-treated/untreated wine grape vineyards in southcentral Washington. Spider mite populations (primarily Tetranychus urticae Koch) were generally small (0-10 mites/leaf) and showed little monthly variation. They were significantly larger in pesticide-treated (season mean: 19.2% of leaves occupied) than in untreated (1.3%) vineyards in 2000. The greatest mite density (65% of leaves occupied/14 mites per leaf) was seen after 13 applications of sulfur in an additional vineyard monitored in 2000. Six species of phytoseiid mites were recorded (Galendromus occidentalis Nesbitt, Amblyseius andersoni [Chant], Typhlodromus caudiglans [Schuster], Typhlodromus pyri Scheuten, Metaseiulus citri [Garman and McGregor], and Metaseiulus flumensis [Chant]). G. occidentalis and M. citri accounted for 80-83% of specimens identified. Phytoseiid populations were larger in untreated (season means: 7.1-9.1% of leaves occupied) than in treated (1.8-4.6%) vineyards and tended to increase in mid to late summer (up to two mites per leaf). Fungivorus tydeid mites were occasionally common in pesticide-treated and untreated vineyards in autumn (up to 73% of leaves occupied). Nymphs of the leafhoppers, Erythroneura elegantula Osborn and Erythroneura ziczac Walsh were more abundant in untreated (season means: 19.4-52.2% of leaves occupied) than treated (3.3-13.1%) vineyards with densities of up to 21 per leaf. Populations peaked in August in 1999 and July in 2000. Thrips nymphs (primarily Frankliniella occidentalis [Pergande]) were equally common in pesticide-treated and untreated vineyards (season means: 12.9-18.2% of leaves occupied) but tended to be more abundant early season in pesticide-treated vineyards. Implications of these results for improved arthropod pest management in Washington grapes are discussed.