Radiation induced F1 sterility in Plutella xylostella (Lepidoptera: Plutellidae):: Potential for population suppression in the field

The potential of using F(1) sterility in a system to manage the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), was investigated in the laboratory and in field-cages. When B-day old male pupae were treated with 200 Gy of gamma radiation, 71.5% developed into normal adults. However radiation-induced reductions in fecundity and viability were expressed during the P(1), F(1), and F(2) generations. Sterility exceeded 60% in the P(1) and F(2) generations and 90% in the F(1) generation. The sex ratio was skewed in favor of males among F(1) and F(2) progeny. The percentages of metaphase spermatogonial cells with chromosomal aberrations mere 86.9, 21.5 and 9.7 in the F(1), F(2), and F(3) respectively. No differences were observed in the sperm transfer between irradiated and unirradiated males. When treated males were released into field-cages at either a 5:1 or a 10:1 overflooding ratio with unirradiated moths, there was a significant reduction in the number of F(1) and F(2) adults emerging in the field-cages as compared to the control. A 50-60% reduction in the F(1) and 59-68% in the F(2) generation were observed. When irradiated females and males were released at a 5:5:1:1 overflooding ratio with untreated DBM, the decrease in F(1) adult emergence was not significantly different than for the control. However, adult emergence in the F(2) generation was reduced by almost 90%. This degree of suppression was significantly greater than that achieved in cages where only irradiated males had been released. The use of F(1) sterility in combination with releases of the parasitoid, Cotesia plutellae (Kurdjumov) (Hymenoptera: Braconidae), in field-cages resulted in a 40% decrease in the DBM population in the F(1) and more than 90% in the F(2) generation. Nevertheless, additional research is needed to develop this system into an economically feasible strategy for managing early season populations of DBM.