Influence of Temperature on Grape Leafhoppers in Southcentral Washington

Abstract

The 2 most important leafhopper pests of grapes in Washington are the Western grape leafhopper, Erythroneura elegantula Osborn, and Erythroneura ziczac Walsh. The influence of different constant temperatures on the egg and nymphal stages of E. ziczac and on the nymphal stage of E. elegantula was examined. Development times of E. ziczac eggs ranged from 33.1 d at 15°C to 8.6 d at 32.5°C. E. ziczac nymphal development ranged from 40.2 d at 16°C to 11.1 d at 29.5°C. The average number of degree-days required for development from oviposition to imaginai molt was 435.4. This was slightly higher than the previously published value of 390.5 DD for field reared E. ziczac. E. elegantula nymphal development ranged from 38.0 d at 16.0°C to 11.8 d at 32.5°C. The average number of degree-days required for E. elegantula development from eclosion to imaginai molt was 246.3. Constant temperature data for the egg and nymphal stages of E. ziczac and for the nymphal stage of E. elegantula was fitted to a developmental model based on enzyme reaction kinetics. The egg and nymphal stages of E. ziczac fitted the model with r2 values of 0.9992 and 0.9990, respectively. The E. elegantula nymphal stage fitted the model with an r2 value of 0.9996. Lethal freezing temperatures for E. ziczac adults collected on 28 Januars, 4 February, and 14 November, 1994 were -27.1, -26.3, and -27.2°C, respectively. Freezing temperatures for E. elegantula on the same dates were -24.6, -24.1. and -25.3°C, respectively.