Biological Observations of Typhlodromus occidentalis (Acarina: Phytoseiidae) on Hops1

Abstract

Longevity, fecundity, and prey consumption of Typhlodromus occidentalis (Nesbitt) were determined at 18.5, 25, and 30°C. At these temperatures, females laid an average of 33.8, 35.2, and 28.2 eggs, respectively. The average female life, span at these temperatures was 27.1, 14.3, and 10.9 days. The number of eggs laid per female per day was 1.21, 2.51, and 2.58. The peak of egg production shifted from a poorly defined peak between 10 and 17 days at 18.5°C to 9 days at 25°C to 6 days at 30°C. Tetranychus urticae Koch reared on beans were used as prey. The number of prey consumed at 18.5, 25, and 30°C were: eggs, 6.2, 9.8, and 11; larvae or protonymphs, 5.8, 8.3, and 8.2; deutonymphs, 2.5, 5.1, and 5.8; and adults, 1.9, 2.5, and 3.6. Overwintering female T. occidentalis emerge about mid-April in Washington hop yards, and are present about 6 weeks. The population then declines to a low level until the prey population develops. Later, T. occidentalis are found on hop foliage feeding on T. urticae from July until harvest in late August or early September. During the years 1969-71, 28 pesticides in 72 combinations were tested for control of hop pests. Phosalone permitted greatest selective survival of T. occidentalis .