Prospecções de Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) para o manejo de Plutella xylostella (L.) (Lepidoptera: Plutellidae)

Abstract

Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) is a parasitoid of several pest species, including Plutella xylostella (L.) (Lepidoptera: Plutellidae), but little is known about its control potential. Therefore, the fertility life table was used to evaluate the reproductive performance of this parasitoid on P. xylostella and the alternative host Tenebrio molitor (L.) (Coleoptera: Tenebrionidae). Furthermore, it was determined whether the natal host (P. xylostella or T. molitor) interferes with the olfactory response and rate of parasitism on P. xylostella. Finally, the survival of the parasitoid was determined when exposed to cyantraniliprole 100 SC (100 ml/ha) and to spinetoram 250 WG (100 g/ha), and 50% of these dosages, in different substrates (inert surface and cabbage leaf) and over time (0 to 8 days) under laboratory conditions. The results showed that T. howardi preferentially parasitizes P. xylostella and T. molitor pupae compared to the larvae of these hosts. The intrinsic population growth rate (rm) ranged from 0.117 to 0.132 ♀/♀*day in P. xylostella, and from 0.152 to 0.167 ♀/♀*day in the alternative host T. molitor, being statistically higher in the alternative host. The parasitoid olfactory response and the rate of parasitism on P. xylostella were not affected by the natal host. Regarding the selectivity of the insecticides tested, exposure via dry residue of both insecticides at the dosage used did not cause mortality in adults of T. howardi. Also the residue of both insecticides did not cause significant mortality, regardless of the exposure period and did not affect the parasitism capacity in P. xylostella, allowing the development of parasitoid descendants. It is estimated that under the conditions of Chã-Grande-PE, where T. howardi was collected on P. xylostella pupae, it completes up to 16 generations/year, while the pest can reach 19 generations/year, respectively. Therefore, T. howardi may contribute to the management of P. xylostella through natural biological control or through inundative releases. Our results also point to the possibility of using this parasitoid together with the insecticides cyantraniliprole and spinetoram, if necessary.