March 21 (UPI) -- Almond growers face a dilemma. They need to keep their almond trees fungus free, but new research shows almond-crop fungicides harm honey bees, the nut tree's chief pollinator.
Lab tests at Texas A&M University show the fungicide iprodione significantly diminishes the survivability rate of western honey bees, Apis mellifera, the world's most common honey bee species.
"Given that these fungicides may be applied when honey bees are present in almond orchards, our findings suggest that bees may face significant danger from chemical applications even when responsibly applied," Dr. Juliana Rangel, assistant professor of apiculture in Texas A&M's entomology department, said in a news release.
Researchers exposed bees to the fungicide -- on its own and in combination with other fungicides -- inside a wind tunnel. The experiments replicated the exposure rates bees experience during aerial crop dusting.
After exposure, bees were monitored in a separate environment for 10 days. Those exposed to the fungicides experienced accelerated rates of mortality. Exposed honey bees were two to three times more likely to die during the 10 days.
"Our results may help to encourage discussions on altering spraying regimes or perhaps finding different ways to apply chemicals in such a manner that takes the biology and behavior of pollinators into account," added Adrian Fisher II, a doctoral student in Rangel's lab.
The research -- published in the Journal of Economic Entomology -- didn't explore the exact nature of the fungicide's harmful effects on honey bees.
Previous studies suggest pesticides can harm bees' gut microbiota and depress their immune system, curtailing bees' ability to fight off infections and parasites.