By Killing Beneficial Insects, Neonic-Coated Seeds Increase Pesticide Dependency, Just Like Other Insecticide Applications
(Beyond Pesticides, December 16, 2016) A new meta-analysis has challenged the belief that neonicotinoid (neonic) insecticide seed coatings have little to no effect on the health of beneficial predatory insect populations —on the contrary, researchers have found that the seed coatings impact predatory insects as much as broadcast applications of other insecticides. The study, authored by Margaret Douglas, PhD and John Tooker, PhD, of Penn State University, solidifies previous work that shows beneficial predators are affected through secondary poisoning as a result of neonicotinoid seed coatings.
For their meta-analysis, the researchers combined the results of approximately 1,000 observations for field studies across North America and Europe that had looked at the effect of neonicotinoid seed coatings on predatory insects. The researchers compiled datasets that compare predatory insect abundance in plots that are planted with coated seeds to control plots, which are either managed without insecticides, or managed with pyrethroid insecticides. As predicted, the population of predatory insects are reduced in the plots where coated seeds are planted, compared to the plots that are untreated by insecticides. Additionally, the meta-analysis finds that coated seeds affected predatory insect populations similarly to soil and broadcast applications of pyrethroids.
Generally, these findings indicate that the use of neonicotinoid seed treatments, which are intended to decrease the use of pesticides, can actually increase the necessity of these toxic chemicals by killing off natural, beneficial insect predators. Thus, these seed treatments are ineffective and cause more harm than good. It would better serve farmers and the environment to actively encourage natural predation, rather than rely on toxic chemicals that only perpetuate the dangerous cycle of escalating pesticide use.
In 2015, another study authored by Dr. Douglas demonstrates that natural enemy insects could be affected by neonic-coated seeds, through a previously unexplored pathway. Dr. Douglas found that seed treatments using the neonicotinoid thiamethoxam, a toxic insecticide that is supposed to affect pest slugs, instead bioaccumulated and then transferred through the slugs into their insect predators, impairing or killing >60%. This resulted in a loss of crop due to a decline in beneficial insect predators and an increase in pest slug population.
This meta-analysis adds merit to the body of research regarding neonicotinoids and their impacts on pollinators and other non-target beneficial species. Neonicotinoids are a relatively new class of insecticides that share a common mode of action that affects the central nervous system of insects, resulting in paralysis and death. While the issue of pollinator declines is diverse and complex, with many factors potentially contributing to the cause, pesticides have consistently been implicated as a key factor, not only through immediate bee deaths, but also through sublethal exposure causing changes in bee reproduction, navigation and foraging. Further research has demonstrated that neonicotinoids create increased vulnerability to diseases through exposure, impact a wide range of habitats, and have persistent, long term implications.
Neonicotinoids are undoubtedly highly toxic to honey bees, and EPA acknowledges this fact. However, little is being done at the federal level to protect bees and other pollinators from these pesticides. With unlimited resources behind them, the chemical industry —the pesticide manufacturers, landscaping, horticultural and agricultural trade groups— have all come out to deflect attention away from pesticides as a major culprit in pollinator decline. To learn more about how industry agents try to manipulate the message to say that neonics are not the main cause, see Beyond Pesticides’ report addressing industry myths on pollinator decline.
In light of the shortcomings of federal action to protect these beneficial creatures, it is left up to us to ensure that we provide safe havens for pollinators by creating pesticide-free habitat and educating others to do the same. Beyond Pesticides has created a small pesticide-free garden at our offices in DC to provide habitat and forage for our local pollinators, including a beehive on site. You too can pledge your green space as pesticide-free and pollinator-friendly. It does not matter how large or small your pledge is, as long as you contribute to the creation of safe pollinator habitat. Sign the pledge today. Need ideas on creating the perfect pollinator habitat? The Bee Protective Habitat Guide can tell you which native plants are right for your region.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.