Parasitismo e desenvolvimento de Tetrastichus howardi (Olliff, 1893) (Hymenoptera: eulophidae) na lagarta-da-soja Anticarsia gemmatalis (Hubner, 1818) (Lepidoptera: erebidae)

Abstract

Tetrastichus howardi (Olliffe, 1893) (Hymenoptera: Eulophidae) is a parasitoid that attacks larvae and pupae of caterpillars. This species is gregarious and polyphagous and it was collected in the pupa of Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) on a sugar cane crop in Dourados, MS. The experiment was performed at the Biological Control of Insects Laboratory (LECOBIOL) at the Federal University of Grande Dourados (UFGD) located in Dourados, MS. This work aimed to assess the capacity of parasitism and the development of females of T. howardi in the larvae of Anticarsia gemmatalis (Hubner, 1818) (Lepidoptera: Erebidae) from the first to the fifth instar and in the pupae depending on the density of this parasitoid females. This work was split into three steps. During the first step, it was assessed the development of T. howardi in the larvae of A. gemmatalis exposed to the ratio 1:1 and 7:1 (parasitoid: host) of female parasitoids for 24 hours of parasitism. Larvae of A. gemmatalis showed parasitism at the two tested densities of T. howardi. The emergence of adults was also assessed. During the second stage, larvae of forth instar (0,998 mm) of A. gemmatalis were exposed to parasitism of females of T. howardi (24 hours old) at the densities of 1:1, 7:1, 14:1 and 21:1, for 24 hours of parasitism (parasitoid: host). Larvae of A. gemmatalis had parasitism of tested females of T. howardi. The adult emergence was also assessed. Contrarily to the first stage, the density of 7:1 and 14:1 showed the best biological characteristics of parasitoids. During the third stage, pupae of A. gemmatalis were exposed to the parasitism of females of T. howardi at the ratio of 1:1 (parasitoid: host) for 24 hours, with parasitism and parasitoids emergence being present. Females of T. howardi were capable of infecting the larvae of A. gemmatalis from the first until the fifth instar. This phenomenon is new and it has not been mentioned in the literature. The ratio of females of T. howardi has influence on both the parasitism and the larval emergence of A. gemmatalis. Females of T. howardi may infect the larva and emerge from the pupa of A. gemmatalis, with the capacity of emerging from the adult when infecting pupa older than 96 hours.