Biology of Cotesia flavipes (Hymenoptera: Braconidae) Strains at Different Temperatures.

Currently the area with the inundative release of Cotesia flavipes (Cameron) in the country is approximately 3.5 million hectares per year in regions of tropical and subtropical climate, but there are questions about its efficiency since they are not considered the thermal requirements of the strains used. The objective of the study was to evaluate the biology in different thermal conditions of five C. flavipes strains, from different places of origin. Insects from Paraná (Strain PR), Minas Gerais (Strain MG), Alagoas (Strain AL) and two strains from São Paulo state (SPI and SPII strains) were submitted to different constant temperatures (10, 15, 18, 20, 22, 25, 30, and 32°C), relative air humidity of 70 ± 10% and 12-h photophase. The duration the egg-adult of C. flavipes was inversely proportional to the temperature in the thermal range of 18 to 30°C. No development occurred at temperatures of 10, 15, and 32°C. The highest survival of the biological cycle (egg-adult) (above 70%) occurred in the thermal range of 25 to 28°C. Also, temperatures from 28 to 30°C characterize significantly more females than males (sex ratio > 0.70). Based on the development of the biological cycle, the threshold temperature (Tt) was similar among the C. flavipes strains (ranging from 9.6 to 11.1°C), providing the thermal constants of 229.4 to 273.9 degree-days. The biological control of Diatraea saccharalis (Fabricius 1794) (Lepidoptera: Crambidae) may be more efficient to use C. flavipes strains more adapted to the thermal conditions of each region.

Importance of Sugar for the Development of Diatraea saccharalis (Lepidoptera: Crambidae) on Artificial Diet.

To obtain insects with biological characteristics similar to those of wild insects, this study evaluated the development of Diatraea saccharalis (Fabricius) reared on artificial diet containing different sugar concentrations. First-instar caterpillars were fed seven artificial diets containing 0, 6.56, 13.13, 26.26, 52.52, 105.04, and 210.08 g of sugar per liter of diet. We evaluated the duration and viability of developmental stages, weight of pupae, fecundity and longevity of generations F1, F2, F4, F6, and F8. The artificial diet containing 26.26 and 52.52 g of sugar per liter provided the greatest viability of insects (above 75%) for the egg-adult period for eight consecutive generations, and was higher (P < 0.05) than other treatments, where viability was lower than 50%. Based on the fertility life table in F8 generation, the highest reproductive rates (Ro) were obtained in insects fed the artificial diet containing 26.26 (Ro = 126.39) and 52.52 g of sugar (Ro = 147.31). Conversely, insects to other diets presented the highest values of biological cycle duration (T = 55 d) and reductions of 50 and 90% on intrinsic rate of increase (rm = 0.0063, 0.079, 0.077, and 0.064) and finite rate of increase (λ = 1.001, 1.082, 1.081, and 1.006), respectively. We conclude that sugar is essential for the development of D. saccharalis and that amounts of 26.26 and 52.52 g per liter of diet are suitable for the rearing and multiplication of insects in laboratory.