Temperature-related development and population parameters for Typhlodromus pyri (Acari: Phytoseiidae) found in Oregon vineyards.

The beneficial mite Typhlodromus pyri is a key predator of grapevine rust mite Calepitrimerus vitis in Pacific coastal vineyards. Rust mite feeding has been associated with damage such as stunted, deformed shoot growth and reductions in fruit yield. The life history traits of T. pyri were assessed at seven constant temperatures (12.5, 15, 17.5, 20, 25, 30 and 35 °C) to determine population parameters providing data to better predict biological control of C. vitis populations by T. pyri in vineyards. Successful development from the egg to adult stage was observed at temperatures ranging from 15 to 30 °C. Constant exposure to 12.5 and 35 °C resulted in 100 % mortality in immature T. pyri. Developmental times, fecundity and longevity were highest at 25 °C. The estimated minimum and maximum developmental thresholds were 7.24 and 42.56 °C, respectively. Intrinsic rate of increase (r ( m )) was positive from 15 to 30 °C indicating population growth within this range of temperatures. Net reproductive rate and intrinsic rate of increase were greatest at 25 °C. These developmental parameters can be used to estimate population growth, determine seasonal phenology and aid in conservation management of T. pyri. Results presented in this study will aid in evaluating the effectiveness of T. pyri as a key biological control agent of C. vitis during different periods of the growing season in Pacific Northwest vineyards.

Impact of vineyard pesticides on a beneficial arthropod, Typhlodromus pyri (Acari: Phytoseiidae), in laboratory bioassays.

Laboratory bioassays were conducted to evaluate the effects of six vineyard pesticides on Typhlodromus pyri Scheuten (Acari: Phytoseiidae), a key predator of the mite Calepitrimerus vitis Nalepa (Acari: Eriophyoidae), in Pacific coastal vineyards. Materials tested were whey powder, 25% boscalid + 13% pyraclostrobin (Pristine), 40% myclobutanil (Rally), micronized sulfur (92% WP), 75% ethylene bisdithiocarbamate (mancozeb; Manzate), and 91.2% paraffinic oil (JMS Stylet), all applied at three concentrations. Pesticide dilutions were directly sprayed onto T. pyri adult females and juveniles, and each treatment was assessed to determine effects on direct mortality and fecundity. Five of the six pesticides tested resulted in < 50% mortality to adult and juvenile T. pyri for all concentrations 7 d after treatment. Paraffinic oil treatments displayed direct mortality > 50% for adult and juvenile assays and resulted in significantly higher mortality. Sublethal effects were more pronounced than acute pesticide toxicity, particularly in juvenile mite bioassays. Significant decreases in fecundity were detected in the sulfur and mancozeb treatments compared with the control in juvenile tests. The relative percentage of fecundity reduction for juvenile mites was highest when applying mancozeb (> 70%), sulfur (> 25%), or myclobutanil (> 20%). Adult mites displayed the greatest reductions in fecundity from applications of paraffinic oil (> 20%) or mancozeb (> 15%) treatments. Boscalid (+ pyraclostrobin) and whey displayed the least effect on fecundity across all bioassays. These results can be used to develop management guidelines in vineyard pest management practices to help conserve and enhance predatory mite populations.