Direct estimation of the survival time of commercially produced adult Trichogramma platneri Nagarkatti (Hymenoptera: Trichogrammatidae) under field conditions

Studies were conducted to estimate survival time of commercially produced Trichogramma platneri Nagarkatti (Hymenoptera: Trichogrammatidae) in a walnut orchard in California. Batches of 23±7 female T. platneri were held in sleeves of dialysis tubing attached to walnut tree branches. Mean time to 50% survivorship of unfed parasitoids was 2.0±0.1 days whereas honey-fed parasitoids lived significantly longer (2.6±0.1 days) than unfed parasitoids. The presence of a leaf within a sleeve also increased mean time to 50% survivorship (2.9±0.2 days), relative to unfed parasitoids. Median survival time was inversely correlated with mean temperature for all treatments. The relationship between degree–day accumulation and survivorship was described using a Weibull function. Survival time in the field was less than expected from comparable laboratory estimates and reasons for these differences are discussed.