Recently I was reading different papers and commentaries about the doubts related to the use of clothianidin (see the figure) in the field due to effects on honey bee survival. According to Jim Frazier, Professor of Entomology at Penn State University, clothianidin is toxic to bees and the pollen that bees take back to their colonies contains the chemical, as does the dust that comes off planters.
“The EPA admits that their testing has not been adequate to determine the impact of this chemical on bees and pollinators” Frazier said, adding that while a direct link between clothianidin and colony collapse has not been established, more studies are needed.
Looking in some blogs I frequently read sentences reporting that “corn seeds are treated with Clothianidin, and if corn leaf aphids can still live on and suck sap from whorl stage corn treated with Clothianidin (whorl stage corn is the stage when tassels and pollen are produced) without the corn leaf aphids dying, or the next generation of corn leaf aphids being born with two heads etc. I see nothing that would suggest that corn grown from seed treated with clothianidin is dangerous to honeybees, little less humans. After all bees are much larger than aphids and honeybees don’t exclusively eat corn sap, like the corn leaf aphid does. Further more bees don’t live exclusively on corn plants like some corn leaf aphids must”.
Actually, different experiments reported that cotton aphid Aphis gossypii is sensitive to clothianidin and there is a low cross-resistance between imidacloprid and clothianidin, so that aphids resistant to some neonicotinoids can be treated with clothianidin killing them. Moreover, honeydew excretion is significantly inhibited in aphids treated with clothianidin avoiding also honeydew related damages to plants.
At present there are several evidences suggesting that clothianidin is highly toxic also to honey bees and it has the potential for toxic chronic exposure to honey bees, as well as other non-target pollinators, through the translocation of clothianidin residues in nectar and pollen. In honey bees, the effects of this toxic chronic exposure may include lethal and/or sub-lethal effects in the larvae and reproductive effects in the queen.
As reviewed some years ago, neonicotinoids are increasingly used for systemic control of plant-sucking insects, replacing the organophosphorus compounds and methylcarbamates, which have decreased effectiveness because of resistance or increased restrictions due to toxicological considerations. Neonicotinoids are also important in animal health care in view of the selective toxicity of the neonicotinoids… but are we still sure of this specificity?
NOTE: What is clothianidin? Chloronicotinyl insecticides (neonicotinoids) were developed as a substitute of nicotine, targeting the acetylcholine receptors. Clothianidin, like other neonicotinoids, is an agonist of the acetylcholine neurotransmitter causing paralysis and death. The advantage of clothianidin and other neonicotinoids over nicotine is that they are less likely to break down in the environment.