INHERITED STERILITY BY SUBSTERILIZING RADIATION IN SPODOPTERA LITURA (LEPIDOPTERA: NOCTUIDAE): BIOEFFICACY AND POTENTIAL FOR PEST SUPPRESSION

Abstract

Spodoptera litura reared on host plants and on synthetic diet were irradiated with two substerilizing doses of gamma radiation, 100 Gy and 130 Gy, and examined for inherited sterility. Irradiation affected mating success in the parental (P) and F1 generations. F1 sterility was higher than P sterility, and F1 males inherited more sterility than did F1 females. F1 progeny developed at a slower rate compared with controls. F1 survival to adulthood decreased with increasing dose of radiation. Sex ratio in F1 moths was skewed towards male. Life tables were constructed for S. litura reared on host plant and synthetic diets, and the impact of radiation on population characteristics was ascertained. Reproductive rate (R0) was significantly decreased as a consequence of irradiation, and the effect was more severe in F1 crosses than in P crosses. There was a negative correlation between the dose of radiation and the percent embryo formation in P crosses. Whereas in F1 crosses, radiation dose (given to male parents) was positively correlated with the percent unhatched embryonated eggs. Early mortality of eggs prevailed in unhatched eggs derived from P crosses, and late embryonic lethality was the major cause of F1 sterility. Effects of irradiation are discussed with an emphasis on assessing the potential of the inherited sterility principle for pest control.