Field Availability and Avoidance of Imidacloprid‐Treated Soybean Seeds and Cotyledons by Birds

Abstract

Treated seeds and their cotyledons can present a toxicological risk to seed-eating birds. To assess whether avoidance behavior limits exposure and consequently the risk to birds, three fields were sown with soybeans. Half of the surface of each field was sown with seeds treated with 42 g/100 kg seed of insecticide imidacloprid (T plot, treated) and the other half with seeds without imidacloprid (C plot, control). Unburied seeds were surveyed in C and T plots at 12 and 48 h post-sowing. Damaged seedlings were surveyed in C and T plots at 12 days post-sowing. The abundance and richness of birds was surveyed at the field level (without distinguishing between C and T plots) before, during, and after sowing, and 12 days post-sowing. Unburied seed density was higher in the headlands of the T plots than in the C plots, but did not differ between 12 and 48 h. The damage to cotyledons of seedlings was 15.4% higher in C plots than in T plots. The abundance and richness/ha of birds that eat seeds and cotyledons were lower after sowing, indicating a deterrent effect on birds by sowing imidacloprid-treated seeds. Although the variation in seed density over time does not allow solid conclusions to be drawn about the avoidance of seeds treated by birds, the seedling results suggest an aversive effect of imidacloprid-treated soybeans on birds. The dominant species was the eared dove (Zenaida auriculata), whose risk of acute poisoning by imidacloprid in soybean seeds and cotyledons was low, according to its toxicity exposure ratio, foraged area of concern, and foraged time of concern.

Diet and Spatial Ecology Influence Red-Legged Partridge Exposure to Pesticides Used as Seed Treatment

“…This lack of association may be because partridges may have been feeding on cereals that were not treated with pesticides, like the left-over plants (i.e., grain and straw) from the previous harvest. Most experimental studies conducted to compare the consumption of treated and untreated seeds indicate that, when both choices are available, birds show a preference for untreated seeds. – ,, This pattern has also been observed in the field. , Therefore, even if untreated seeds were less available than treated seeds in the study area, partridges might have selected, when possible, uncontaminated seeds, which could explain the lack of association between consumption of cultivated plants and exposure in partridges. Also, even if coming from treated seeds, the materials taken by partridges could have reduced pesticide loads either because of environmental degradation or because of pesticide dilution by plant growth, if the consumed materials are germinated seeds or shoots .…”

“…[36][37][38]46,47 This pattern has also been observed in the field. 48,49 Therefore, even if untreated seeds were less available than treated seeds in the study area, partridges might have selected, when possible, uncontaminated seeds, which could explain the lack of association between consumption of cultivated plants and exposure in partridges. Also, even if coming from treated seeds, the materials taken by partridges could have reduced pesticide loads either because of environmental degradation or because of pesticide dilution by plant growth, 50 if the consumed materials are germinated seeds or shoots.…”