Weekly shipments of Trichogramma pretiosum Riley, Trichogramma minutum Riley, and Trichogramma brassicae (Bezdenko) (Hymenoptera: Trichogrammatidae) from a single insectary were assessed to determine whether survivorship with and without honey, emergence rate, and sex ratio were consistent over a five-week period in 2000. At least one shipment was misidentified by the insectary. Emergence rates were over 75% in 15 out of 17 shipments, although emergence varied significantly over the experimental period for each species. Mean longevity of honey-fed individuals was 7.16 days for T. pretiosum, 6.71 days for T. minutum, and 4.02 days for T. brassicae; mean longevity of unfed individuals was 2.68 days, 2.42 days, and 1.96 days, respectively. Mean sex ratios (proportion of individuals that were male) were 0.029 for T. pretiosum, 0.465 for T. minutum, and 0.444 for T. brassicae. Seventeen out of 18 virgin T. pretiosum females produced daughters, and three out of a subset of six of these females produced sons after being fed the antibiotic tetracycline. These results are consistent with infection by a parthenogenesis-inducing strain of Wolbachia.
Bibliographical noteFunding Information:
We thank Seth Bomgren, Randy Hedlund, Amanda Jacobson, and Sara Smith for their assistance with data collection for this study; Beneficial Insectary for providing the wasps and irradiated host eggs used in the experiments; and Dr. John Pinto for identification of wasps received from the insectary. This research was funded by the North American Pesticide Impact and Assessment Program Grant #660, and the Minnesota Department of Agriculture Biological Control Granting Program. This research has been supported in whole or in part by the University of Minnesota Agricultural Experiment Station.
- Biological control
- Natural enemies
- Quality control