AMES - As concern continues to mount over the continuing decline in honey bee numbers, an Iowa State University researcher said there are several causes contributing to the population drop in all pollinators - not just honeybees - around the world.
"Each cause compounds the others," said Amy Toth, an assistant professor of ecology, evolution and organismal biology at ISU, and one of the researchers in a report released Jan. 30 that analyzed the numbers loss. "People want a single issue to blame it on, and that would be great because we could fix it.
"But it's not that simple."
A pair of researchers work with bee hives at a Cherokee County study site.
Toth described the decline as "a complex business" with the need to "unravel" all possible causes with each layer of the problem.
"Each factor and layer of the problem leaves the bees (and insects) more susceptible to the next," she said.
A good place to start, however, could be the dwindling variety of diet available to pollinators with urban sprawl and expanded agricultural production.
"These two factors have squeezed out in recent decades the diversity of flowering plants giving access to a wide range of flower pollen," she said.
The resulting diminished nutrition weakens the bees and heightens their vulnerability to pesticides and viruses.
She pointed specifically to those viruses carried by parasitic mites encountered more often in recent years.
"When you combine worsening nutrition with limited habitat and an uptick in viruses, the predicament faced by pollinating insects comes into clearer focus."
Other researchers and agencies, including the U.S. Department of Agriculture, have shared a similar concern as USDA statistics point to a bee decline of upward to 33 percent each year since the early 2000s.
Andrew Joseph, state apiarist with the Iowa Department ofs Agriculture and Land Stewardship, said average annual winter American bee losses over the last five years in Iowa is "nearly a third."
According to May 1, 2013, report by USDA's Agricultural Research Service without complete disappearance of the bees can cause an increase in needed pollination services translating into higher food costs for consumers.
Dr. Mary Harris, an ISU adjunct assistant professor joining with Toth, said she has welcomed the opportunity to contribute research to a team organized by the non-profit, California-based Pollinator Partnership to study the cause of the falling honeybee numbers.
Harris' portion of the research was conducted in Buena Vista, Cherokee and O'Brien counties in northwest Iowa with six cooperators. The producers and experimental site owners - four private landowners and ISU's Allee Memorial Demonstration Farm, in Newell, and Northwest Research Farm, in Sutherland, cooperated with the project.
"State of the art planters use air pressure and powder lubricants to plant individual seeds," said, Harris an instructor in natural resource ecology and management. "During planting, some of the treated coating on the seeds rubs off, mixes with the lubricant and is exhausted.
"It's a dusty process, and that's what spreads the pesticide," she said in the release.
"The study doesn't prove that neonicotinoids (insecticides commonly used to coat seed corn) are responsible for the widespread collapse of bee colonies in Corn Belt states," Harris said. "But it does show that pollinating insects are being exposed to pesticides inadvertently.
"We have to consider what sort of impact that exposure could be having on them."
She said her own concerns focus on the "non-target" effects of neonicotinoid seed treatment on insects that are not plant pests.
"I am a proponent and practitioner of IPM, or Integrated Pest Management, in which scouting for pests and determining if pest numbers warrant a treatment or not is a regular part of operations," she said. "By using any insecticide only when necessary you help maintain that insecticide's efficacy for when it is needed for control of a specific pest."
In Sioux City, meanwhile, Leonard Kurtz, a 48-year beekeeper and now retired SueBee Honey employee, terms the dwindling bee numbers resulting from "a tug of war" between chemical companies, food suppliers and producers.
"As the world population continues to grow," Kurtz said, "the chemical and fertilizer companies and farmers are teaming up for food production efficiency and to maximize the production of every acre.
"In the process, chemicals are being used to control insects and are getting into our food supply. This has had a negative effect and become a burden for the honeybee."