Use of dry bean fields by birds and mammals in Brazil: Insights from a field study and its use in pesticide risk assessment.

The relationship between agriculture and wildlife can be both synergetic and challenging, as the increased surface of agricultural land makes it increasingly important for agriculture and wildlife to coexist. This study aims to describe the use of freshly drilled dry bean fields by birds and mammals in Brazilian Cerrado and Atlantic Forest sites and their diversity and abundance within in-crop and off-crop areas (with native permanent vegetation and other surrounding crop fields) at four different farms. A comprehensive survey was conducted, using various sampling methods, including point counts, foraging counts, trail cameras, and occasional encounters. In all, contacts for 12 518 birds across 306 species and 313 mammals across 34 species were registered. The off-crop areas exhibited greater species richness, abundance, and diversity than the in-crop areas on all farms. For birds, 47 species were recorded in-crop, of which 15 were classified as insectivores, 15 as granivores, seven as omnivores, seven as carnivores, and three as frugivores. The number of in-crop observations per species was small. The abundance off-crop was greater for 31 species observed in-crop, indicating that dry bean fields are probably not a preferred habitat for those species. Species classified as granivorous are most likely to feed on dry bean seeds. However, almost all granivorous species observed in-crop areas are too small to be able to feed on dry bean seeds. For mammals, nine species were recorded in-crop, of which four were classified as carnivores, three as omnivores, one as insectivore, and one as granivore. Additionally, despite the considerable effort in this study, no evidence was found that birds and mammals feed on dry bean seeds. The results highlight the importance of off-crop areas in dry bean fields, characterized by a more diverse and abundant bird community than in-crop. Integr Environ Assess Manag 2024;20:864-874. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Dust abraded from thiamethoxam-treated seed during sowing: Refining the risk assessment for native bees in Brazil.

During sowing using pneumatic machinery, dust may be abraded from pesticide-treated seed and contaminate adjacent bee-attractive off-crop areas. This study quantified the risk to native bees of dust released during sowing of Brazilian crop seeds treated with a thiamethoxam formulation (Cruiser 350FS). To address toxicity to native bees, adult acute contact LD50 data for thiamethoxam were collated from the literature, a species sensitivity distribution generated, and the HD5 calculated. The LD50 HD5 was used to refine the default safety factor applied to the honeybee acute contact LD50 from 10 to 5.45 for thiamethoxam. Crop-specific abraded dust data (Heubach dust and Heubach AI) were generated for seeds treated with Cruiser 350FS sourced from on-farm and industrial facilities. The mean Heubach dust levels was ranked as cotton = maize > sunflower = soybean > drybean. There was no correlation between the measured residues of thiamethoxam (Heubach AI) and those estimated in dust based on the thiamethoxam content of Cruiser 350FS. A hazard quotient (HQ) for each crop (based on application rate, the default dust deposition factor, and the honeybee contact LD50/10) identified risks during sowing for all crops. Refinement of the application rate with the measured 90th percentile Heubach dust (assuming 100% thiamethoxam) resulted in sowing of industrially treated soybean and on-farm treated cotton being identified as risks. Further refinement using either the measured 90th percentile Heubach AI or the acute contact LD50 (HD5 ) resulted in sowing of all crops treated with Cruiser 350FS as being identified as low risk. Similar high quality seed treatment should be demonstrated for other formulations containing insecticides with high toxicity to bees. Data on dust drift from machinery and crops more representative of those in Brazil may allow further refinement of the default dust deposition value of 17% used in this study. Integr Environ Assess Manag 2023;19:1361-1373. © 2023 SETAC.

Sugar levels modulate sorbitol dehydrogenase expression in maize.

The first step in sucrose use by maize kernels produces fructose, regardless of whether the initial reaction is catalyzed by an invertase or the reversible sucrose synthase. This fructose can enter subsequent metabolism via hexokinase, or in maize kernels, by a sorbitol dehydrogenase that reversibly converts fructose + NADH to sorbitol + NAD. High levels of SDH activity suggest that kernels synthesize considerable amounts of sorbitol, but the molecular mechanism and functional role for this process have remained equivocal. To gain insights on the role of sorbitol synthesis in maize endosperm we cloned and characterized the transcriptional control of the maize sorbitol dehydrogenase (Sdh1) gene. Data indicated that Sdh1 was essentially kernel- and endosperm-specific, with maximal expression at both the mRNA and enzyme activity levels during early kernel development. Expression was elevated in high-sugar mutants (sugary1, shrunken2), also by sugar injections, and was more pronounced when transfected tissues were incubated at low oxygen concentrations. Control of Sdh1 expression in our transient assays was largely dependent on the first intron of Sdh1. We speculate that SDH activity may represent an adaptation to the high-sugar/low-oxygen environment of the endosperm. Under these conditions, the NADH-dependent reduction of fructose to sorbitol would regenerate NAD[+], thus contributing to the maintenance of the redox and energy status of the cell.