Popular insecticides tied to bee health
A popular family of insecticides came under further scrutiny recently when a pair of studies published in the journal Science linked bee exposures to those insecticides to a drop in hive health.
In a response to the studies, insecticide manufacturer Bayer CropScience said the studies used higher than normal levels of neonicotinoid insecticides, and results contradicted results found in previous studies using “fieldlevel” amounts of the insecticides. The neonicotinoid class includes clothianidin (Poncho) and thiamethoxam (Cruiser), which are found on most treated corn, soybean and canola seed.
Bee experts have struggled in recent years to find answers to a dramatic drop in several bee populations. Pesticide exposure is one of the theoretical factors associated with so-called colony collapse disorder (CCD).
A statement from Bayer said that its product, clothianidin, underwent some 30 studies involving affects on pollinator insects like bees before being registered for use by the Environmental Protection Agency.
In a telephone interview with DTN, Iain Kelly, Bayer bee health team lead, said that while he found the recent studies “intriguing” in terms of the technology used in them, he believed the results point to the continued need for studying all the factors that are potentially involved in bee and hive health.
“We don’t think these studies, by themselves, point to any need for immediate changes in the way neonicotinoids are used,” Kelly said.
He said the company has been expanding its research on bee health, including a continued look at the role the Varroa mite plays in CCD.
“In the studies we’ve seen, there is rarely a consistent connection to any one thing that causes colony collapse disorder,” Kelly said. “The one thing we know that consistently leads to lower bee populations is the Varroa mite, and hope all this interest in bees re-invigorates that research.”
The studies published last month, one from the United Kingdom and one conducted in France, found that bees given a dose of the pesticides were associated with poorer performing hives. In one case involving bumblebees, hives with treated bees produced fewer queens. Another study used honeybees with microchip tracking devices and those treated bees were found less likely to find their way back to the hive. Other studies have pointed to a possible link between the insecticides and effects on bees’ central nervous system.
Neonicotinoids made headlines in early February when a Purdue University study revealed that small amounts of the insecticides found in excess planter-box talc could be toxic to bees if the talc fell on flowers or other nearby vegetation where bees were attracted.
Purdue entomologist Christian Krupke investigated reports of bee deaths occurring at planting times in hives near Indiana agricultural fields during 2010 and 2011. Analysis of bees found dead in and around the hive showed presence of neonicotinoids. The researchers also found clothianidin and thiamethoxam at low levels in the soil—up to two years after treated seed was planted, according to the report.
Kelly said that in all cases, conversations around proper insecticide stewardship are growing. In a March interview, Kelly told DTN that the company is always evaluating alternative coatings and stickers that bind the insecticide to the seed. — Greg D. Horstmeier, DTN