Desempenho biológico de Tetrastichus howardi (Hymenoptera: eulophidae) em lagartas, pupas e pré-pupas de Anticarsia gemmatalis (Lepidoptera: erebidae) em condições de laboratório e semi-campo

Abstract

The pupal and larval endoparasitoid Tetrastichus howardi (Olliff, 1893) (Hymenoptera: Eulophidae) lepidoptera pest has the potential to be used in biological control programs, and has been studied as a potential agent for use in biological control programs with an emphasis on principal pests of important cultures. The objective of this study was to evaluate the biological characteristics of T. howardi in fourth instar larvae, in pre-pupae and pupae of the alternative host Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Erebidae), with different densities of female parasitoids in laboratory and semi-field conditions.The bioassays were conducted at the Laboratório de Controle Biológico de Insetos (LECOBIOL), and the semifield test conducted in a greenhouse at the Universidade Federal da Grande Dourados (UFGD). In the first laboratory test, caterpillars were individualized in Petri dishes containing diet and exposed to parasitism by different densities (1: 1, 5: 1, 10: 1, 15: 1, 20: 1 or 25: 1, parasitoid: host ) for 96 hours. In semi-field, 4 caterpillars were distributed per plant pot, containing two soybean plants, individualized in cages (80x50 cm). Subsequently, 4, 20, 40, 60, 80 or 100 females of T. howardi were released, representing the same proportions used in the laboratory, remaining in these conditions for a period of 96 hours. After the parasitism, the females were removed and the caterpillars were individualized in Petri dishes containing a portion of the diet fed until death or progeny emergence, remaining in a climatic chamber (BOD) at 25 ± 1ºC, 70 ± 10% of UR and photophase of 14 hours. In the following bioassays, pre-pupae and pupae were exposed to parasitism by T. howardi females at different densities (1: 1, 5: 1, 10: 1, 15: 1, 20: 1 or 25: 1, parasitoid: host) and after 24 hours the parasitoid females were removed and the hosts were transferred to glass tubes (15x1 cm) at 25 ± 1 ° C, 70 ± 10% RH. In the first work, it is possible to conclude that 1 T. howardi female is able to parasitize and develop on 4th instar larvae of A. gemmatalis in the laboratory and cause mortality in semi-field conditions. In the second work, we can conclude that T. howardi successfully parasitized pre-pupae and pupae of A. gemmatalis, allowing us to consider the range of 5 to 10 T. howardi females the most suitable for multiplication of this parasitoid in the laboratory. In general, the results allow us to suggest this parasitoid as a potential biological control agent.