Applied Pesticide Toxicity Up in the US, Even in GM Crops

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A recent study (Item 1) in the journal Science shows that, contrary to claims of reduced environmental impacts of pesticide use, the toxicity of applied insecticides to aquatic invertebrates and pollinators has more than doubled between 2005 and 2015 in the US, in sharp contrast to the applied amount. A shift towards usage of pyrethroids and neonicotinoids, respectively, is responsible for this trend. This pattern is evident even for GM crops that were originally designed to reduce pesticide impacts on the environment (Item 2).

The toxicity of pesticides depends not just on amount applied, but on which pesticides are used. This is why the researchers looked at the type, amount, and toxicity of 381 pesticides applied in the US over the last 25 years. The researchers call the toxicity arising from pesticides applied to crops the “Total Applied Toxicity (TAT)”.

For GM crops, the researchers report increasing toxicity of applied pesticides to aquatic invertebrates and pollinators in GM maize and terrestrial plants in herbicide-tolerant soybeans since approximately 2010. Considering only data for maize, of which 79% in the US in 2016 was Bt hybrids, TAT increased for both aquatic invertebrates (mainly because of pyrethroids) and terrestrial pollinators (mainly because of neonicotinoids) at the same rate observed for US agriculture as a whole. The toxicity per hectare of insecticides applied to Bt maize is equal to that for non-Bt maize. The researchers suggest that the increasing insecticide TAT may be a result of preemptive, possibly unnecessary applications or pest resistance to the Bt toxins in Bt maize. (Item 3)

The researchers also report that herbicide use has increased with the spread of herbicide-tolerant GM crops, which has led to a strong increase in the use of glyphosate. The TAT to terrestrial plants has increased steadily since approximately 2008 for herbicides in herbicide-tolerant soybeans, likely in response to glyphosate resistance.

This study highlights the overall trend in the US: while over the years, there has been a reduction in the volume of insecticides sprayed on fields, the insecticides currently applied are much more toxic (Item 4). Consequently, there has been a significant increase in the environmental impact due to pesticides, with and without GM plants. The researchers recommend “a system-centric view” of pest management in agriculture and suggest that organic agriculture can provide one of several useful strategies.

- Third World Network

Source: https://science.sciencemag.org/content/372/6537/81