Influência do pólen de milho bt e não bt sobre o consumo, massa adquirida e sobrevivência de larvas e adultos de Apis mellifera L.

Abstract

The benefits offered by Bt plants are numerous, such as being less impactful to the environment than agrochemicals. There is, however, concern about the possible harmful effects on non-target insects such as the possibility of their toxins being transmitted by pollen and affect the development of Apis mellifera. Thus, this study aimed to evaluate the effects of Bt corn pollen, compared to non-Bt pollen on the development of larvae and adults of these pollinators. The work was carried out from the sowing two varieties of corn [BALU 188 RR (non-Bt) and BALU 280 PRO (Bt toxins with Cry1A.105 and Cry2Ab2)] in the agricultural year 2015. The plant pollen was collected during the full bloom. The bees (larvae and adults) were collected from a nearby hive exposed to the maize crop. Two bioassays were performed with larvae (test 1) and adults (test 2). The maintenance of the larvae in the laboratory was held on bees handmade wax domes. The adults were kept in suitable plastic containers, also in the laboratory. Insects (larvae and adults) were maintained in a temperature of 32 ± 2°C and RH 70 ± 10%, due this conditions are the nearest found in the inside of the hive. In test 1 were offered seven diets (treatments): pure honey; diet with 20, 40 and 80 mg of maize pollen variety of BALU 188 dissolved in 1 ml of honey solution of 10% water; and diet of 20, 40 and 80 mg of maize pollen variety of BALU 280 PRO dissolved in 1 ml of honey 10% solution in water. In trial 2 the same treatments were offered with honey solution and, in addition, also candy paste: paste pure candy; diet with 20, 40 and 80 mg of BALU range of 188 maize pollen dissolved in 1 g of candy slurry; and diet of 20, 40 and 80 mg of maize pollen variety of BALU 280 PRO dissolved in 1 g of paste candy. The acquired mass, mortality and survival of the larvae, as well as the mass consumed diet and mortality of the adults were assessed daily during the experiment. The experimental design was completely randomized, with seven treatments and ten repetitions for the larvae and fourteen treatments and ten repetitions for adults. The data were submitted to analysis of variance and mean test. Pollen levels were subjected to regression analysis. The data, after being subjected to statistical analysis, concluded that the mass gained by larvae was influenced by the origin of the pollen (Bt and non-Bt) and, in the case of Bt, also the dose used in the diet. Larvae fed diets consisting of Bt pollen, except the lowest concentration showed less weight gained that diets composed of non-Bt pollen. Bt pollen doses adversely affected the mass acquisition, according to adjusted regression model. Since the mortality of larvae can be influenced by the amount of pollen in the diet because the higher the dose the higher the percentage obtained used, regardless of the variety (Bt and non-Bt). The mean mass diets consumed by adult bees for the honey and composed of candy binder, were statistically significant according to the quantity and quality (Bt and non-Bt) pollen. The adults feed over diets comprised of honey solution, compared with candy folder. The results of the regressions from pollen doses on the analyzed parameters were only significant analysis to the candi folder with non-Bt pollen, where there was positive quadratic effect of pollen dosages on the mass consumed. The mortality is higher and, furthermore, early, when it happens consumption of high doses of maize pollen, the most evident and severe effects in those with Bt technology. According to the results, it is noted that Bt pollen when in high concentration in the diet affects some characteristics of adults and larvae of Apis mellifera.