Técnicas de criação em laboratório e dispersão do parasitoide de pupas Trichospilus diatraeae (Hymenoptera:Eulophidae) no campo.

Abstract

The pupal endoparasitoid Trichospilus diatraeae (Hymenoptera: Eulophidae) is a preferential parasitoid of the order Lepidoptera, and is utilized in several biological control programs. However, the efficiency of pest control through natural enemies varies due to biotic and abiotic factors. The development of techniques that enable the commercial-scale cultivation of natural enemies is one of the basic points for mass release in management programs. The present work aims to refine techniques for mass rearing and storage of the alternative host Spodoptera frugiperda and for storing and dispersing the adult parasitoid to control defoliating caterpillars in commercial eucalyptus-production areas. The experiments were completed in the Laboratory for Biological Control of Forest Pests at FCA/UNESP - Botucatu Campus and at the farm Manto Verde in Lençois Paulistas, Sao Paulo state, Brazil. S. frugiperda pupae were raised on an artificial diet, while the parasitoid T. diatraeae was removed from the breeding stock of the laboratory. The experiment sought to evaluate the optimum parasitism density in the following ratios 1:1, 7:1, 14:1, 21:1, 28:1 and 35:1. Positive intraspecific interference was verified up to the density 28:1, with parasitism and emergence rates above 90% and total progeny of 269.2 parasitoids, thus showing the best density for mass production questions to reflect positively on biological characteristics. Studies on parasitoid behavior must include direct interference of diet in parasitism. Six feed types were tested on parasitoid females: pure honey, 10% honey, hemolymph, hemolymph + honey, distilled water and absence of food. Honey was shown to be the most suitable diet, by providing high levels of parasitism, emergence above 100%, total progeny of 264.7 parasitoids, positively interfering in the biology of these insects. Also discussed was the optimum exposure time of alternative host pupae to parasitoid, tested at 24 hours, 48 hours, 72 hours and 96 hours. The greatest

emergence rate (above 90%) and total progeny (above 280 parasitoids) occurred at 72- and 96- hour moments, thus showing these exposure times superior for implementing a mass production system. The influence of host storage at low temperatures on parasitoid biological characteristics was tested by storing pupae at five, eight, 10 and 25ºC for periods of one five, eight and 10 days. From storage of alternative host pupae, we can conclude that parasitoid biological characteristics degrade as storage time elapses, at all temperatures. Continuing storage studies in this experiment evaluated the biological characteristics of T. diatraeae females when stored at low temperatures of 10, 18, 22 and 25ºC, for one, five, eight and 10 days; the result demonstrates that there was no statistical difference among the storage temperatures in relation to the storage periods, showing that the parasitoid can be stored at low temperatures for different periods without losing biological characteristics. To measure the dispersal of the parasitoid T. diatraeae 50,000 parasitoids were released into a central experimental area and evaluated in the four cardinal directions (north, south, east and west) for the pupae and in four collateral directions (northeast, northwest, southeast and southwest) for the number of parasitoids in yellow traps at five distances, in concentric circles, at five, 15, 30, 60 and 100 m. Parasitism was increased in direct proportion with the distance from the release point at distances above 30 meters, with mean of 24.8%, with the highest parasitism rate (37.9%) at the greatest distance. The number of insects in the traps did not differ statistically between the southeast and northeast collateral directions at any distance, with the higher number of insects in the southeast region. The wind oved to[ be th[e[[ main [factor resp[onsible for the dispersion of these parasitoids in these conditions.