RESUMO
The genus Diabrotica has over 400 described species, the majority of them neotropical. However, only three species of neotropical Diabrotica are considered agricultural pests: D. speciosa, D. balteata, and D. viridula. D. speciosa and D. balteata are polyphagous both as adults and during the larval stage. D. viridula are stenophagous during the larval stage, feeding essentially on maize roots, and polyphagous as adults. The larvae of the three species are pests on maize, but D. speciosa larvae also feed on potatoes and peanuts, while D. balteata larvae feed on beans and peanuts. None of these species express a winter/dry season egg diapause, displaying instead several continuous, latitude-mediated generations per year. This hinders the use of crop rotation as a management tool, although early planting can help in the temperate regions of the distribution of D. speciosa. The parasitoids of adults, Celatoria bosqi and Centistes gasseni, do not exert much control on Diabrotica populations, or show potential for inundative biocontrol plans. Management options are limited to insecticide applications and Bt genetically modified (GM) maize. Other techniques that show promise are products using Beauveria bassiana and Heterorhabditis bacteriophora, semiochemical attractants for monitoring purposes or as toxic baits, and plant resistance.
RESUMO
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.
