Mite diversity in organic and conventional vineyards

Abstract: Phytoseiid mites (Acari) can be very effective natural enemies of herbivorous mitesin vineyards. Apart from climatic conditions and grape variety effects, the abundance anddiversity of these predators in vineyards is mainly influenced by the presence of suitable foodresources and the vineyard management. Therefore, the effects of the vineyard management(organic versus conventional) and the cover crop diversity (high versus low) on prey mites andphytoseiid mites were evaluated in Austrian vineyards. The preliminary data from the firstevaluation in May indicated that the cover crop diversity did not affect mite abundance anddiversity independent of the vineyard management. Furthermore, the abundance of potentialprey mites (Tydeoidae, Eriophyidae) on vine leaves was not affected by the managementmethods. However, the diversity of phytoseiid and eriophyid mites, and also the populationdensities of phytoseiid mites were significantly higher in conventional vineyards than in organicvineyards. The most parsimonious explanation for these findings might be the applications offungicides based on the vineyard management methods. In contrast to conventional vineyards,fungicides containing the active substances sulphur and copper are more frequently used inorganic vineyards than in conventional vineyards. These active substances are known to havedetrimental effects on phytoseiid mites, which might be responsible for the reduction ofpredatory mite populations in the previous year and the low densities of the overwinteringpopulations this year.