Biology and thermal requirements of Trichogramma pretiosum Riley and T. exiguum Pinto & Platner (Hymenoptera: Trichogrammatidae) reared on eggs of Plutella xylostella (L.) (Lepidoptera: Plutellidae)

This biology of Trichogramma pretiosum Riley and T. exiguum Pinto & Platner in Plutella xylostella (L.) eggs was studied at seven constant temperatures, and the thermal requirements and number of generations of both parasitoids was determined for some crucifers producers of the states of Espírito Santo and Pernambuco. Eggs of P. xylostella were submitted to parasitism by T. pretiosum and T. exiguum for 5h, and transferred to climatic chambers regulated to 18, 20, 22, 25, 28, 30 and 32ºC. The developmental time was influenced by the temperature varying from 6.8 to 23.1 days for T. pretiosum and 6.9 to 22.0 days for T. exiguum at 32 and 18°C, respectively. The percentage of emergence was higher at 28ºC, reaching 86% for both species. The sex ratio was always 1 for T. pretiosum and varied from 0.6 to 0.9 for T. exiguum. The thermal constant (K) and base temperature (Tb) were higher for T. exiguum (129.99 days degrees and 13.13ºC) when compared with T. pretiosum (123.03 days degrees and 12.52ºC). The estimated number of annual generations of T. pretiosum and T. exiguum for Gravatá district was 36.9 and 36.7 generations respectively. The same number, however for Muniz Freire, ES, was 24.1 and 24.5, and for Alegre, ES, 26.7 and 27.0 generations for T. pretiosum and T. exiguum respectively.

Insecta; diamondback moth; biological control; parasitoid; cabbage