New studies question the use of insecticides with neonicotinoids, allowed as an emergency resource | Science


Protest against the use of insecticides with neonicotinoids last September in Paris.
Protest against the use of insecticides with neonicotinoids last September in Paris.CHARLES PLATIAU (Reuters)

Not infrequently, political decisions collide with scientific studies, and agriculture is a common battlefield. The European Food Safety Authority (EFSA) has considered “justified” the emergency use in 11 States of insecticides with neonicotinoids in sugar beets during 2020 and this past year. However, several recent investigations warn that these products, which are the most used in the United States, not only contaminate the soil and aquifers, but also, in addition to killing bees, poison other beneficial insects for the pollination and pest control as well as their food.

Beetroot Beta vulgaris vulgaris, the main raw material for obtaining sugar industrially in Europe, has been treated in the last two years with neonicotinoids, a family of insecticides chemically similar to nicotine that acts on the central nervous system of insects. Despite their use being prohibited since 2018 in the EU, some countries continue to authorize them when they consider that there is “a danger to crops that cannot be tackled by other reasonable means”, an exception provided for in the EU Regulation. This has been the case in Germany, Belgium, Croatia, Denmark, Slovakia, Spain, Finland, France, Lithuania, Poland and Romania.

The ban is based on the fact that EFSA considers it proven that some of the substances that make up these insecticides (imidacloprid, thiamethoxam and clothianidin) pose risks to the health of bees and that the use of thiacloprid could lead to contamination of groundwater. However, the same entity has considered the authorizations for emergency use justified in the last two years, “either because there were no alternative products or methods (chemical or non-chemical) or because there was a risk that the plague could become resistant to alternative products available ”.

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The Business Association for Plant Protection (AEPLA) defends the use of neonicotinoids when “there are no viable alternatives” and defends that “up to 40% of the potential production of crops in the world is lost annually by pests and diseases”

However, an international consortium of researchers from the Valencian Institute of Agrarian Research and the University of Valencia (Spain), the University of Wageningen (Holland) and those of Minnesota and Pennsylvania (United States) has published in Biological Reviews an investigation in which, after four years of study, they identify not only the risks of the use of these insecticides for bees but also for the rest of beneficial insects as biological control agents and pollinators as well as new indirect routes of extension of the toxic products.

Poison in the food of insects

A previous work of this group, published in Proceedings of the National Academy of Sciences (PNAS) has already demonstrated the use of neonicotinoids, in addition to killing bees and polluting the environment, they indiscriminately kill beneficial animals and cause poisoning of honeydew excreted by insects that feed on plants previously treated with systemic insecticides . This molasses, the main source of carbohydrates, if not the only one in cases of limited flowering monocultures, is toxic to insects that feed on it and are essential for pest control and pollination.

The honeydew produced by aphids, mealybugs, whiteflies or psyllids (hemiptera insects) is the main food of biological pest control agents, such as ladybugs, lacewings, parasitoids and ants, and of some pollinators such as bees, syrphids and other pollinating flies.

When plants or seeds are treated with neonicotinoids, the honeydew produced by insects that feed on it is also toxic and, therefore, the contamination also affects the species that ingest it. Studies have shown that between 30 and 40 days after treating soybeans treated with insecticides, the aphids of this plant became resistant to the lower concentrations while the molasses they excreted was poisonous to beneficial insects.

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In this way, while pests become tolerant or resistant to systemic insecticides in large monoculture areas that lack nectar such as cereals (corn, wheat, barley, or rice, among others), which occupy more than 50% of the world acreage (723 million hectares, three quarters of the surface of Europe), the honeydew they produce becomes toxic to the insects that ingest it and these and their beneficial functions disappear.

From nectar to molasses

Miguel Calvo-Agudo, from the Valencian Institute of Agrarian Research and main author of the studies, highlights the importance of the research: “The paradigm of exposure routes changes because everything was considered for nectar and now molasses is also included as a factor risk in evaluations of the environmental impact of insecticides “

“The impact”, adds the researcher, “is higher for beneficial insects than for harmful ones; those that originate the pests, many times, become tolerant or resistant to these insecticides while in pollinating species, for example, the effects are very serious ”.

EFSA justifies its decision to authorize emergency uses of neonicotinoids in the absence of “alternative methods (chemical or non-chemical)”. Calvo-Agudo believes that there are and that insecticides should be “the last resort to use, even though they are currently being used first.” The researcher points out that they are used preventively by treating the seeds before the problem appears and that some, as he warns, “can remain in the environment for years.” “As they are soluble,” he explains, “if they are applied on a plot, they can reach other lands through water or even accumulate in rivers and lakes. Then the plants absorb the insecticide again ”.

The impact is higher for beneficial insects than for harmful ones; those that cause pests, many times, become tolerant or resistant to these insecticides while in pollinating species, for example, the effects are very serious

Miguel Calvo-Agudo, Valencian Institute of Agricultural Research

The scientist assures that experience shows that there are options to treat the fields: “It has been seen that there are many cases in which biological control works 100%, but it requires that the farmer know exactly what pest he has and treat it very specifically. It is more complex, the producer has to be much more trained and, perhaps, it can be more expensive in the short term, but, once the beneficial insects have been installed, they will work for many more years and increase the yield of the crops. ; are some of the advantages of biological control ”.

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EFSA itself, in justifying the use of neonicotinoids for beet, includes alternatives to pests: early planting, biocontrol measures, crop rotation, avoiding tillage and control of weeds that are host to harmful insects. Calvo-Agudo adds more formulas. “Biological conservation control consists of introducing plants between crop lines that increase populations of beneficial insects and can be more efficient in attacking pests.”

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George Holan

George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.

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