Gypsy moth F1 sterility programme: Current status

In the United States of America the gypsy moth, Lymantria dispar (L.), is progressively invading the country from its original site of introduction in Massachusetts. The use of F1 sterility is being developed to eradicate the isolated infestations that occur sporadically far beyond the generally infested zone. F1 sterility is also being developed to retard the rate of expansion of the generally infested zone. The optimal dose to induce F1 sterility appears to be 80 Gy of gamma rays. Pilot trials are being carried out in which treated male pupae are distributed into the wild, or in which the F1 progeny of treated males and normal females are distributed during the egg stage. The latter approach permits mass rearing during most of the year and the stockpiling of diapausing eggs, as well as simplified shipment and distribution. In the past, mass rearing proved to be somewhat unreliable because of the occurrence of 'abnormal performance syndrome' or APS. This syndrome is characterized by a poor hatch, high mortality of neonates and retarded larval development. The syndrome is diet related, and can be avoided by fastidious attention to meeting the nutritional requirements of the rearing stocks. A special container was designed for the shipment and release of pupae. Also, a special formulation of the pheromone was developed that appears to permit the correlation of trap catches with local egg mass densities. Released males are marked internally with Calco red dye or externally with a fluorescent dye. Also, a morphometric method has been developed to distinguish between wild and released moths. F1 males mate readily, but the frequency of sperm transfer is low. Nevertheless, wild females mated to F1 males appear to behave as through they had been mated to normal males. (author)