Effects of Four Physical Treatments of Oothecae ofPeriplaneta americanaon Parasitism and Development of Parasitic WaspEvania appendigaster

Abstract

Periplaneta americana (L.) is one of the major hygienic pests distributed worldwide. Evania appendigaster (L.) is a parasitic wasp species of oothecae of P. americana and could, therefore, be used in the control of P. americana. Before releasing the parasitized oothecae, however, it is important to inhibit embryogenesis of P. americana to prevent them from hatching. Hence, the objective of this study was to investigate the effect of four physical treatments (freezing, heating, UV irradiation, and gamma irradiation) on the hatchability of the treated oothecae and also to measure the parasitism rate, emergence rate, and developmental time of E. appendigaster in the treated oothecae. The results revealed that P. americana hatched from UV-treated oothecae, whereas the eggs receiving the other three treatments did not hatch. The results also indicated that, except for the oven-heated oothecae, those receiving the other three treatments had no effect on the parasitism rate of E. appendigaster. In addition, the freezing treatment had the highest impact on the emergence rate and developmental times of E. appendigaster, with <20% emergence. Overall, our results suggested that gamma irradiation had the lowest impact on the parasitism rate, emergence rate, and the developmental times of E. appendigaster. The application of parasitized oothecae to P. americana habitats, such as sewer networks, together with bait control, may effectively reduce the population of P. americana.