|JOSEPH-J.B., Sylvia - FLORIDA A&M UNIV.|
|Bloem, Ken - USDA, APHIS|
|Mizell, Iii, Russ - UNIV. OF FLORIDA|
Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2003
Publication Date: November 30, 2003
Citation: Joseph-J.B., S., Bloem, K., Reitz, S.R., Mizell, Iii, R. 2003. Use of radiation to sterilize two-spotted spider mite (acari: tetranychidae) eggs used as a food source for predatory mites. Florida Entomologist. 86:389-394. Interpretive Summary: Predatory mites are important as augmentative biological control agents of two-spotted spider mites in greenhouse crops. Currently, these predatory mites must be reared on live spider mite prey; thus, shipments may be contaminated with live spider mites. As an alternative to the use of live prey, scientists with USDA-ARS and APHIS at the Center for Medical, Agricultural, and Veterinary Entomology, in collaboration with scientists from Florida A&M and the University of Florida, are investigating the effect of radiation on the viability of two-spotted spider mite eggs and their acceptability as prey for predatory mites. Their results demonstrate that egg hatch decreases as radiation dose increases; however, older eggs require higher doses of radiation to prevent egg hatch than do younger eggs. In general irradiating spider mite eggs had no significant effect on their acceptability as prey by females of the predatory mite Neoseiulus californicus McGregor. These results indicate that irradiated eggs could be used by producers of predatory mites as a food source when shipping the predators to eliminate concerns about also shipping live pest mites.
Technical Abstract: One-, 2- and 3-day old two-spotted spider mite eggs were treated with increasing doses of gamma radiation ranging from 0-280 Gy. Percent egg hatch decreased as radiation increased for each age group; however, older eggs required higher doses of radiation to prevent egg hatch than did younger eggs. Based on the regression lines for 1-, 2- and 3-day-old eggs, the best estimates of the doses of radiation that would prevent 100% of the eggs from hatching were 43.6 Gy, 55.1 Gy and in excess of 280 Gy, respectively. In general, irradiating spider mite eggs had no significant effect on their acceptability as prey by females of the predatory mite Neoseiulus californicus McGregor, except for 1-day-old eggs treated at 240 Gy. Female N. californicus consumed 50-75% fewer of these eggs than they did eggs of other treatments, in both no-choice and choice experiments.