Camouflaging of seeds treated with pesticides mitigates the mortality of wild birds in wheat and rice crops

Abstract

Seeds used to plant wheat, corn and rice crops in Brazil are treated with the insecticide carbofuran associated with the dye rhodamine B, attracting granivorous birds and causing mortality during sowing. The objective of this study was to evaluate if using camouflaged seeds can minimize mortality caused by the ingestion of seeds with carbofuran. Alternatives for reducing mortality, such as using carbofuran without rhodamine B or replacing carbofuran by carbosulfan, were compared. Three experiments were carried out in regions of known bird mortality in the states of Paraná and São Paulo, Brazil, using conventional sowing over plowed soil in the traditional planting system, 15,896 kg of seeds in 111.46 ha. Bird carcasses were collected and dissected to unveil which poisoned seed treatments had caused birds' deaths. The mortality mounted to 296 birds of 11 species. Eared doves were the most numerous casualties (263). There was significant correlation between mortality and number of consumed seeds. The consumption of camouflaged seeds was lower than that of commercial seeds treated with rhodamine B. The mortality caused by seeds with both rhodamine B and carbofuran was higher than mortality caused by seeds camouflaged only with carbofuran. The replacement of carbofuran with carbosulfan also seemingly reduced mortality, but carbosulfan mortality might have been underestimated as a result of the apparent movement of affected birds after exposure. Seeds treated with carbofuran and rhodamine B and without any dye, were attractive. Because legal requirement for seeds treated with pesticides to be differentiated by dying, the substitution of rhodamine B by camouflaging must be encouraged.

Camouflage of Seeds, a Control Method of the Bird Mortality in Grain Crops

“…Although fewer birds died when carbosulfan was used, as in the previous trial and experiment, many birds visibly affected by carbosulfan escaped the test plot, making an accurate estimation of mortality difficult. Although previous experiments have shown the relative efficacy of methiocarb as a secondary repellent to birds (Nelms & Avery 1997;Avery et al 2001;Avery 2002), its use in association with carbofuran did not generate results showing it to be a mitigating factor in bird mortality, probably because carbofuran is an extremely toxic pesticide, needing only one treated seed to kill a small or medium sized bird (Almeida et al, 2010a). Thus the toxicity of carbofuran would overrun any of the potentially beneficial effects of methiocarb.…”

“…An study consolidating three experiments was conducted in Paraná and São Paulo States to evaluate if camouflaged seeds could minimize the mortality of wild birds, caused by the ingestion of commercial seeds treated with pesticides and rhodamine B (Almeida et al, 2010a). When put all together, the three experiments were summing up to 15,896 kg of seeds, sowed in 111.46 hectares.…”

“…These aspects are contrary to the use of carbosulfan and other products, which are up to 20 times less toxic than carbofuran, for the treatment of seeds or as gustative repellents. The authors had concluded, if seeds treated with pesticides must receive a different color to prevent accidents with humans, the camouflaging method may be used for mitigating the mortality of birds in plantations, substituting rhodamine B (Almeida et al 2010a). Another study focusing on mitigation methods was realized consolidating two experiments, witch compares the environmental impacts associated with the use of carbofuran, carbosulfan and methiocarb-treated seeds, with the latter two carbamate compounds being considered as alternatives to carbofuran, and all coloured with Rhodamine B (Almeida & Almeida, in press).…”

“…Poorly developed sense of taste is a plausible hypothesis to explain the limited results of some authors, using chemical repellents in the absence of alternative food sources for birds: Avery et al (1998) with anthraquinone, Moran (2001) metil antranilato, Almeida et al (2010a) with carbosulfan, Almeida & Almeida (in press) employing carbosulfan and methiocarb. Taking the example of these cases, when grain stained with 'aversive' colors were used, there were also ingestion rates (Avery et al, 1999, Hartley et al, 1999, 2000 which can result in high mortality rates in situations where the density of birds is high.…”

“…This can be inferred, considering that, despite the lack of consumption of blue color seeds in some experiments (Hartley et al, 1999, 2000, Almeida et al 2010b) the use of carbofuran in the granular formulation of the same color has been banned in Virginia, USA and Canada, due to bird mortality caused by direct ingestion of the product (Almeida et al, 2010b). Moreover, there has been no communication observed between poisoned birds and healthy ones, that could stop the consumption, even when expressive mortality rates occur and in the presence of obvious agonistic behaviors caused by the ingestion of seeds treated with carbofuran, methiocarb carbosulfan or in combination with conspicuous colors such as beige and red (Almeida et al, 2010a;Almeida & Almeida, in press). In these experiments, it was noteworthy that gustative repellents (carbosulfan and methiocarb) were superseded by the fact that carbofuran has the unpleasant distinction of being so hazardous to wildlife, that it simply cannot be effectively regulated or managed accordingly without mortality risk occur (Richards & Mineau, in press).…”