Use of radiation to sterilize two-spotted spider mite (acari: tetranychidae) eggs used as a food source for predatory mites

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.