ABSTRACT. Brazil has only one public genetic pool of Bombyx mori strains, which was established in 2005 at Universidade Estadual de Maringá, Maringá, Paraná State. This genetic bank has been maintained, and the strains have been characterized using genetic and morphological tools. The quantitative and qualitative traits, directly or indirectly related to productivity, were evaluated in 14 silkworm strains. In addition to biological and productivity analyses, DNA markers related to susceptibility to the B. mori nucleopolyhedrovirus (BmNPV) were analyzed. BmNPV is a major cause of production loss and is a serious problem for Paraná sericulture. The silkworm strains from diverse geographic origins were found to have different characteristics, including body weight, larval stage duration, cocoon weight, and other biological traits. In terms of productivity, the raw silk percentages were almost uniform, with an overall average of 16.28%. Overall, the Chinese strain C37 gave the best performance in many of the quantitative traits, and it surpassed the other strains in productivity Genetic characterization of Brazilian B. mori germplasm bank traits. Therefore, it can be used as one of the strains that compose the elite germplasm for silkworm breeding programs. Additionally, genetic molecular markers were efficient in discriminating between B. mori strains that had been identified based on their geographical origin. We found that all Japanese strains produced a 400-bp molecular marker that has been associated with susceptibility to BmNPV.

The commercial insecticide Fastac Duo is a combined insecticide, widely used in different crops, acting on insects, affecting both pests and pollinators, such as bees. In this study, the effects of sublethal concentrations of Fastac Duo in stingless bees Scaptotrigona bipunctata were evaluated. Worker forager bees were exposed to the insecticide and histochemical and morphological analyses were conducted after 24, 48 and 72 h of ingestion. Brain analysis of S. bipunctata revealed changes in the chromatin condensing state according to exposure time and insecticide concentration when compared to the control group. Morphological changes were observed in the midgut in all concentrations and exposure times, which may interfere in several physiological processes. In conclusion, although the concentrations used in the study did not cause high mortality, it induced changes in the internal morphology that can lead to changes in bee activity.

The silkworm Bombyx mori feeds exclusively on mulberry leaves and is highly sensitive to pesticides in general. Although mulberry plantations are free of agrochemicals, pesticide drift can occur. Chlorantraniliprole, a novel insecticide of the anthranilic diamides class, has been used to control pests in field crops. In this study, we investigated the biological effects of different concentrations of chlorantraniliprole on B. mori silkworm commercial Brazilian hybrids. To evaluate the toxicity of chlorantraniliprole, bio-assays were carried out and data on the lethal concentrations, symptomatology, morphology and variables of silk production were collected. Results indicated that B. mori is extremely sensitive to chlorantraniliprole, even in low concentrations. The highest silkworm mortality rates were observed in the two highest chlorantraniliprole concentrations, 0.2 and 0.1 ppm. Although lower chlorantraniliprole concentrations did not cause death of all the silkworm larvae, various symptoms of toxicity were observed: feeding cessation, regurgitation, late development and incomplete ecdysis. Such symptoms reflect the morphological changes we observed in the midgut epithelium, which affected nutrient uptake and metabolism, and even the production of cocoons. Exposed larvae also produced thin-shelled cocoons, which constitutes a serious economic problem because this type of cocoon is not useful for the silk industry. The results provided herein confirm the toxicity of chlorantraniliprole in silkworm larvae. Therefore, we strongly suggest that, competent authorities of the National Health Surveillance Agency, in pesticide management should take measures to reduce or eliminate the use of chlorantraniliprole in areas nearest to silkworm cultivation.

The meliponines can be found in tropical and subtropical regions and is observed in the majority of Latin America. Scaptotrigona bipunctata are stingless bees that build colonies that possess between 2,000 and 50,000 individuals. This study aimed to estimate the toxicity of the insecticide acephate after oral and contact contamination in S. bipunctata. Results revealed differences between the two types of contamination and indicated that S. bipunctata is tolerant to acephate since the mortality rate was low. The findings indicated that there were expression changes of isoenzyme esterases after contamination with the insecticide, which was able to partially inhibit almost all of the enzymes identified in this study. In addition, morphological changes were identified in the midgut of the bees in the first 24 hours of contamination. However, after 48 hours it was observed the regeneration of the peritrophic membrane and other structures, contributing to the survival of the insects. It is essential to propose measures to minimize the impact of agrochemicals on pollinators and this study provides support for investigations on pesticide toxicity in stingless bees.

Beginning in 2006, beekeepers on the east coast of the United States began to report severe declines in their honeybee colonies. Because of the severity and unusual circumstances of these declines, scientists have called this phenomenon colony collapse disorder (CCD). In 2019, 500 million dead bees were found in Brazil. Analyzes of dead bees identified agrochemicals in approximately 80% of them. Thus, it is believed that one of the main causes for CCD is the intensive use of agrochemicals. Neonicotinoids are the most widely used class of insecticides in the world, they are used for pest control in a variety of crops. However, they can not only affect insects considered pests, but also non-target organisms, such as pollinators. This class of insecticides is divided into five main active ingredients: imidacloprid, thiamethoxam, clothianidin, thiacloprid and acetamiprid. Several studies demonstrate that sublethal concentrations of these insecticides affect bees in different ways, such as navigation memory and muscle movements. Thus, this review aims to report the studies published between 2014 and 2019 regarding the contamination of bees with sublethal doses of the five active ingredients of the neonicotinoid class. Imidacloprid and thiamethoxam are the most used insecticides of this class and show high toxicity to bees. On the other hand, clothianidin showed the least sublethal effects on bees on the studies reported on this review. Thiacloprid and acetamiprid, although less used in agriculture, also impair several aspects of bee health. Thus, it is possible to infer that neonicotinoids are contributing to the disappearance of bees worldwide.