Exigências térmicas e hídricas de Trichospilus diatraeae (Hymenoptera: eulophidae) em pupas de Diatraea saccharalis (Lepidoptera: crambidae)

Abstract

The potencial of Trichospilus diatraeae Margabandhu and Cherian, 1942 (Hymenoptera: Eulophidae) for control of Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) in sugar cane in Brazil is little known.Therefore, this study aimed to evaluate the effect of temperature and relative humidity of air the biology of T. diatraeae reared on pupae of D. saccharalis, for its production in the laboratory. Initially it was investigated if the biological characteristics of T. diatraeae pupae reared on D. saccharalis would be affected by different levels of temperature. Pupae of D. saccharalis aged 24 hours old were exposed to parasitism by seven females of T. diatraeae aged 48 hours, allowed to parasitism for 24 hours. After this period the females of T. diatraeae were removed and pupae transferred to acclimatized chambers at 16, 19, 22, 25, 28 and 31oC, 70 ± 10% relative humidity and photoperiod of 14 hours, maintained at temperature constant. Increasing the temperature reduced the cycle time T. diatraeae, being 31º C, the parasitoid has not completed its life cycle in pupae D. saccharalis. The progeny of parasitoids per pupa ranged 43 to 632 individuals and was highest at 25oC. The base temperature (TB) and thermal constant (K) of this parasitoid were 9.37 ° C and 257.60 day-degrees respectively. The average number of generations per year of T. diatraeae reared on pupae of D. saccharalis, based on the average temperature of 10 years in the city of Dourados, Mato Grosso do Sul was estimated 18.49 generations per year, while this number for D. saccharalis was 5.38. The estimated number of generations of T. diatraeae pupae of D. saccharalis for the cities of Dourados, Ivinhema, Ponta Pora and Tres Lagoas, Mato Grosso do Sul was 18.49, 18.00, 15.83, and 20.36 respectively. In the second experiment, it was investigated if the biological characteristics of T. diatraeae pupae reared on D. saccharalis would be affected by different levels of relative humidity. Pupae of D. saccharalis, with 24 hours of age were isolated in glass tubes (14 cm high x 2.2 cm in diameter) with seven females of T. diatraeae 48 hours old, being allowed to parasitism by 24 hours. After this period, females were removed and the pupae transferred to acclimatized chambers at 25oC, the relative humidity of 40, 50, 60, 70, 80, and 85% and photophase of 14 hours. The best results of biological characteristics (percentage of parasitism and Emergency cycle of life, progeny and sex ratio) of T. diatraeae reared on pupae of D. saccharalis were obtained when using the 25°C and relative humidity of 80%, so we suggest this combination to create T. diatraeae in the laboratory.