Fungicide affects on beneficial arthropods in western Oregon vineyards

Fungicide trials were conducted in western Oregon grape vineyards over two seasons (2008 and 2009) for control of powdery mildew; and to study the timing and effect of seasonal fungicide sprays (sulfur, synthetics, and whey) on grape leaf rust mite, Calepitrimerus vitis (Nalepa) and beneficial arthropods. Leaf samples were collected for pest and predatory mite counts; motile natural enemies were enumerated from seasonal visual assessments and canopy shake samples at 14-day intervals from late May until mid-October. Consistent differences in abundance of predatory arthropods between treatments were not detected, although there was a trend for fewer predators in plots treated with sulfur. Rust mite abundance was not consistently affected by all fungicide treatments. Increased numbers of rust mites were observed in plots treated with synthetics only, but predatory mites and macro-arthropod numbers did not appear to be affected. Sulfur treatments reduced pest mite populations with some negative effects observed on predatory arthropods. This pest management research has demonstrated the value of abundance and diversity of the beneficial organisms contributing to pest reductions. The most populous inhabitants of the Oregon vineyards included: Coccinellid spp. (e.g., Coccinella septempunctata, Cycloneda spp., Harmonia axyridis (Pallas)), Stethorus sp.; predatory bugs including Orius spp. (O. tristicolor and O. insidious), Nabis spp., Deraeocoris spp.; lacewings such as Chrysopa sp. and Chrysoperla sp.; six-spotted thrips (Thysanoptera: Scolothrips sexmaculatus), micro-parasitic Hymenopterans (Chalcidoids and Braconids), and four spider families (Araneae: Salticide, Linyphiidae, Thornisidae, and Clubionidae). The most predominant predacious mites observed were Anystis sp. (Anystidae) and Typhlodromus pyri (Phytoseiidae).