Researchers aim to strengthen bee pollinator populations

by George Jared ([email protected]) 807 views 

Neelandra Joshi, associate professor of pollinator health, fruit entomology, IPM and pesticide toxicology, shows how masonry bees build nests in tubes designed to simulate the kind of cavities the bees prrefer to use for nesting. (UA System Division of Agriculture photo by Fred Miller)

The first ancestors of modern bees were aggressive, carnivorous wasps that roamed the Earth more than 120 million years ago. As the years passed, the hunters morphed into nectar collectors and in doing so became the primary pollinators in nature worldwide.

Bees are critical in food cultivation but in recent decades the number of bee colonies has sharply declined and is a significant threat to the world’s food supply. Scientists in Arkansas are doing research that could lead to ways to protect the world’s bee populations.

Olivia Kline, an entomology doctoral student at the University of Arkansas, works in the research program of Neelendra Joshi, associate professor of entomology for the Arkansas Agricultural Experiment Station. He specializes in research on pollinator health, fruit entomology, integrated pest management and pesticide toxicology.

Their research focuses on blue orchard bees, a type of mason bee native to Arkansas and many other areas in the U.S. Joshi said they are easy to identify because of their iridescent blue color. They nest in tunnels left behind by other insects, like the galleries carved out of trees and wood structures by boring beetles.

Joshi said the characteristic feature of mason bees is the females use mud to build chambers in the tunnels and lay one egg in each chamber. They lay eggs containing female bees in the deepest chambers and males in the chambers closest to the entrance.

“The males emerge first,” Joshi said. “Then they hang around waiting for the females to emerge so they can mate with them.”

Like many bee species, Joshi said, the males have only that one job. The females collect pollen and nectar, which they roll into balls of food for the emerging larvae and place them in the chambers where they lay the eggs. Although classified as solitary bees because only one female uses each nest, blue orchard bees are social in that they like to build their nests near other blue orchard bees’ nests.

“They are gregarious,” Joshi said.

Kline said the bees are not aggressive toward people and the males couldn’t sting if they wanted to because they have no stinger. That makes them ideal research subjects when the researcher is going to spend a lot of time observing them. Joshi said blue orchard bees are native pollinators and valuable to many fruit crops, including tree fruits.

Several factors, often interacting, have been implicated in the decline of wild bee populations like blue orchard bees, Kline said. The decline of the bee population across the world has been dramatic. Wild and domestic honey bees pollinate about 80% of the world’s food supply and pollinate nearly all flowers, according to Greenpeace International.

Worker bees females) live about six weeks in the summer and several months in the winter. Colonies produce new worker bees continuously during the spring and summer, and then reproduction slows during the winter, Greenpeace reported. A bee hive or colony population will decline up to 10% during the winter and replace those lost bees in the spring. In a bad year, a bee colony might lose 15% to 20% of its bees.

In the U.S., winter losses have commonly reached 30%-50% or more. In 2006, David Hackenberg, a beekeeper for 42 years, reported a 90% die-off among his 3,000 hives. U.S. National Agricultural Statistics show a honey bee decline from about 6 million hives in 1947 to 2.4 million hives in 2008, a 60% reduction. The number of working bee colonies per hectare provides a critical metric of crop health. Among U.S. crops that require bee pollination, the number of bee colonies per hectare has declined by 90% since 1962. The bees cannot keep pace with the winter die-off rates and habitat loss, according to Greenpeace.

The causes?

“Increased pesticide use in both rural and urban settings, climate change and pathogens contribute to bee declines,” she said. “But habitat loss remains one of the primary drivers.”

Kline and Joshi realized many farms have available land — along fence lines, around barns, chicken houses and other buildings — where native plants could grow without taking crop land or pasture out of production. Kline said the aim of her research is to investigate whether the addition of native floral resources in an area can help support native bee species while improving the nutrient quality of the soil.

Joshi said establishing a variety of native flowering plants can help restore nutrients and organic matter in soils depleted by many years of monoculture crop production, perhaps reducing farmers’ reliance on commercial fertilizers and other soil amendments. Kline’s research includes analyzing the soils in test plots of native plant mixes to measure fertility improvements.

“A significant improvement in soil health could be an added benefit, and perhaps an inducement, for farmers who opt to add wildflowers to their land to support bee populations,” Joshi said.

In a field on the Division of Agriculture’s Milo J. Shult Agricultural Research and Extension Center in Fayetteville, Kline has erected 12 bee habitats — wood-framed structures covered in black netting — to serve as test plots.

Four of the plots have a buckwheat monoculture, Kline said. Four have a wildflower mix targeted for honeybees and the remaining four contain a wildflower mix aimed more generally at pollinators of all species. Into each habitat, Kline placed 20 female and 10 male blue orchard bees. Later, she raised the population count to 30 and 15, respectively.

The habitats also contain wooden blocks with holes drilled to serve as nesting sites. The blocks come apart so the scientists can observe the nesting sites to see whether the bees are mating, collecting and storing food, and laying eggs.

The research will continue through the summer before evaluating the results, Kline said, but a couple of things are becoming apparent. For example, although honeybees can thrive on buckwheat, the blue orchard bees are not doing well in the habitat planted with only that one species.

“We’ve already found some dead bees,” Kline said.

The bees will be evaluated for fitness by measuring offspring body weight, larval development time and adult emergence from the nests. The soils in the habitats will be analyzed for nutrient content and microbial communities. Kline will conduct comparative analyses to reveal whether the native flower mixes had a positive effect on soil quality as well as bee development when compared to the monoculture control habitats.

For her native bee health research, Kline received a highly competitive graduate student grant from the U.S. Department of Agriculture Sustainable Agriculture Research and Education Program, Joshi said. She also received a Doctoral Academy Fellowship from the University of Arkansas.

Kline hopes to determine what mixtures of wildflowers work best to support native bee species. She also hopes to demonstrate soil fertility benefits of establishing the native plants.

“Wild bees are key players among pollinating insects and contribute greatly to American agriculture by pollinating for fruit and vegetable crops. Maintaining healthy pollinator populations is essential for agriculture in Arkansas and elsewhere,” Joshi said.

“The addition of natural habitat and native flowers to a crop system can provide benefits to sustainable agriculture that greatly outweigh the costs,” Kline said. “This study investigates the direct benefits that floral diversity can have on pollinators, soil and agriculture as a whole.”