University of Nebraska-Lincoln entomologists continue to help shed light on the global bee crisis.
In the third year of a four-year, $4 million USDA multi-state grant given to 16 U.S. universities, Marion Ellis and Blair Siegfried, entomologists in the Institute of Agriculture and Natural Resources at UNL, and other scientists across the country are studying factors affecting honey bee health that have led to significant losses in the critical insect population.
Ellis said many hoped the group would find a single cause of the losses, but instead, it is more of a cumulative effect of many things.
UNL research specifically is looking at pesticides and effects of certain varroacide and fungicide combinations on honey bee health, Ellis said.
Varroacides are used to kill mites preventing them from destroying bee colonies. Varroa mites first appeared in the U.S. in 1987. Fungicides are used to prevent fungus on orchard crops.
Bees are required to pollinate hundreds of flowering fruit, vegetable, seed and nut crops. Without bees, these crops are unable to produce.
So far, research at UNL has indicated some varroacides are significantly more toxic to honey bees when applied together.
Similarly, varroacides, also can become more toxic to bees when they are exposed to some a fungicides used on orchard crops.
"This suggests that beekeepers should avoid applying these varroacides when honey bees are placed in orchards or other crop settings where exposure to sterol biosynthesis inhibiting fungicides is likely," he said.
Normally varroacides and fungicides are well-tolerated by honey bees, but pre-exposure to a sterol biosynthesis inhibiting fungicide like prochloraz increased the honey bee toxicity of fluvalinate, a varroacide used by beekeepers, by a ratio of nearly 2,000 times in the most extreme case.
Coumaphos and fenproximate – two other miticides used by beekeepers – exhibited a lower, but significant, increase in toxicity to honey bees pre-exposed to prochloraz.
This summer, colony level experiments will be conducted to assess the effects of exposure to simultaneously applied field-relevant doses of miticides and fungicides on brood survival, weight gain and queen performance.
1984: Bee problems began
Ellis said honey bee problems started in 1984 with the appearance of the tracheal mite, an organism that lives in the respiratory system of the honey bees. This was followed by the arrival of the varroa mite, followed by Africanized bees in 1990. In 1998, the small hive beetle was discovered, followed by the Nosema ceranae parasite and the Israeli acute paralysis virus in 2007.
While these things are taking a toll on bees and beekeepers, Ellis said his Extension beekeeping programs had record participation this year.
"It seems people are concerned and see keeping bees as a way to help the problem," he said.
A rapid increase in the acreage of insect-pollinated crops, especially almonds in California, compounds the problem, Ellis said.
The U.S. is the leading producer and exporter of almonds and supplies the vast majority of the world's almonds. Half of the country's bees are used to pollinate almonds, which need two colonies of bees for each acre.
Most of the honey bee colonies that produce honey in Nebraska and other north central states travel to California each winter to meet the demand for pollination.
Nebraskans can take steps to help the bees. When possible, instead of having all grass pastures, lawns, parks and golf courses, incorporate blooming plants.
Bees need resources throughout the season and diverse resources are better than monocultures. Some forbs that are highly attractive to bees include clovers, vetches, alfalfa, sunflowers, various mints and most native prairie wildflower mixes.
Beneficial trees and shrubs include pussy willow, linden, black locust, butterfly bush and Russian sage.
The single most important thing people can do is have a diverse set of resources that bloom throughout the growing season, Ellis said.
"You can have 100 acres of a blooming crop, but once the blooms are gone, bees have to look for something else," he said. "In a natural setting, there is succession of blooming things to benefit pollinating insects."
Finally, it's important that people use insecticides carefully – read and follow all label directions and don't spray during blooming periods. It is illegal to spray most insecticides when plants are in bloom.