Parasitismo e desenvolvimento de Tetrastichus howardi (Hymenoptera: eulophidae) em lagartas e pupas de Diatraea flavipennella (Lepidoptera: crambidae)

Abstract

Tetrastichus howardi (Olliff, 1893) (Hymenoptera: Eulophidae) is an endoparasitoid with potential as biocontrol agent. This study aimed et to evaluate the parasitism of T. howardi up on Diatraea flavipennella (Box, 1931) (Lepidoptera: Crambidae), in addition to determining its survival under different regimes of temperature and food availability, further, preference between larvae or pupae with choice and not-choice tests were run and host location in sugarcane plants. The experiments were conducted at the Laboratório de Ecologia e Controle Biológico de Insetos, in the Laboratório de Patologia de Insetos and in the Laboratório de Comportamento de Insetos, as well as in the Área Experimental of the Departamento de Agronomia-Entomologia of Universidade Federal Rural de Pernambuco – UFRPE, Recife – PE. The first experiment consisted of exposing larvae 2nd to 5th instar and pupae of D. flavipennella and Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) to one single female of the parasitoid for 24 or 96 hours of parasitism. The parasitism of pupae was greater than 87% at 24 hours of exposure, both in D. flavipennella and D. saccharalis, while parasitism of larvae reached maximum 14% at 96 hours. We can conclude that T. howardi can be an important biological control agent against sugarcane borer pupa. The survival of T. howardi was inversely proportional to temperature increase, regardless of the feeding condition. Likewise, regardless of temperature, parasitoids fed daily showed greater longevity. Feeding prior to release of the parasitoid, in addition to prolonging its survival in conditions of 18 or 20 °C, may help in the maintenance of the parasitoid in the laboratory until the moment of release. T. howardi parasitized more pupae, than caterpillars in conditions of chance and with no chance of choice, besides the emergence of descendants only in pupae. Regarding the location and parasitism of D. flavipennella caterpillars and pupae by T. howardi, 70% and 33% originated adults respectively, demonstrating that the pupa stage was the one with the greatest influence due to parasitism, hindering the development. The overall outcome of this study suggest that T. howardi has potential to complement Biological Control Program already established against sugarcane borer using braconid wasp that attacks primarily larvae; while, the studied parasitoid prefers pupae of sugarcane borers of D. flavipennella and D. saccharalis.