Caracterização de parâmetros biológicos e seleção de espécies e/ou linhagens de Trichogramma West. (Hymenoptera : Trichogrammatidae) visando o manejo fitossanitário de Trichoplusia ni (Hubner) (Lepidoptera : Noctuidae)

Abstract

Trichoplusia ni (Hübner) (Lep.: Noctuidae) is a pest of great importance in horticulture, because of the use of wide range of hosts. The control of this pest is basically done with chemical insecticides. The use of egg parasitoids of the genus Trichogramma is an alternative for biological control of lepidopteran-pest. However, for the efficiency of these parasitoids are needed studies regarding selection of species and/or strains considering the environment and hosts. Thus, the performance of two strains of Trichogramma exiguum Pinto & Platner, six strains of Trichogramma pretiosum Riley, Trichogramma atopovirilia Oatman & Platner, Trichogramma acacioi Brun, Moraes & Soares, Trichogramma marandobai Brun, Moraes & Soares and Trichogramma demoraesi Nagaraja (Hym.: Trichogrammatidae) parasitizing eggs of T. ni were studied. The biological parameters evaluated were: percentage of parasitism and viability, sex ratio and number of individuals emerging per egg of the host. T. pretiosum strain (Tpsd) obtained the best performance in the parameters of the percentage of parasitism and viability. Based on these results, the influence of the host densities and age of the host was investigated for T.pretiosum strain (Tspd) at 20, 25 and 30 ºC. The proportion of eggs of T. ni offered, at the threetemperatures, influence number of eggs parasitized, percentage of parasitism and individuals emerged per egg. In addition, the best ratio of host egg per Trichogramma, regardless of temperature studied, was 15:1. Eggs up to 24 hours in any temperature allowed the best performance in the biological parameters measured, except in the number of individuals per egg. Thus, T. pretiosum exhibited better performance parasitizing eggs up to 24 hours of age and with host ratio of 15 eggs per female.