PMN Crop News Homepage   



Posted 26 September 2014. PMN Crop News.


Bug-Friendly: Profiting From Beneficial Insects on Farms


Source: Crop Science Society of America Press Release. www.crops.org


Madison, Wisconsin (September 15, 2014)--Ask Sam Rose about bees, and he will tell you they aren’t all equal. “In my opinion,” he says, “honeybees are just not the best bees for pollinating blueberries.” Rose would know. Since 1982, he has been cultivating 200 acres of highbush blueberries on the North Carolina coastal plain. The plants thrive in the acidic, sharp-draining soil at Rose’s Lake Creek Farm in Ivanhoe. But they need bees to grow berries.

 

“I had used bumble bees in the past, but they were so expensive I didn’t feel I was getting value for what I was spending,” Rose says. “I tried the orchard mason bee, but it wouldn’t wake up after the winter.”

As it turns out, some of the world’s best blueberry pollinators were already in the area: an assortment of native bees, including Habropoda laboriosa, the aptly-named southeastern blueberry bee.

Says Rose, “Normally, blueberries are one of the very first things to bloom in the spring. That’s why the southeastern blueberry bee is so interesting because it hatches right on time when the blueberries bloom. And it does a very good job of pollinating blueberries.”

Rose values his native bees so much that he has gone out of his way to make them happy: “The more I can get bees to forage close by, the more I’ll have the following spring.”

He puts out boxes to shelter overwintering native bumble bees and limits insecticide use when bee activity is high. He tried moving bee-pleasing weeds, like Maryland meadow beauty, from fields to fallow areas.

And he flattened eight large mounds of soil, excavated to create irrigation ponds, and planted the resulting half-acre plots with buckwheat.

“So the blueberry blooms,” says Rose, “and then the [wild] gallberry, and then the buckwheat comes into bloom right behind the gallberry.” Not only do the bees feast on a succession of nectar-rich flowers, but the buckwheat foliage and seeds feed wild turkeys and deer—which Rose hunts—and quail, an elusive delicacy in these parts.

As an added bonus, he says, the fast-growing buckwheat “helps keep some of those animals out of my blueberry fields. It gives them something else to eat other than my blueberries.”

Rose discovered empirically what researchers are now beginning to document scientifically: Managing farmland to promote biodiversity and maximize ecosystem services can yield big benefits.

Pollinators mean business

How big? Hannah Burrack, an associate professor of entomology at North Carolina State University (NCSU), says bee diversity is worth $7 million a year to North Carolina blueberry growers, or $1.4 million for each of five functional species groups, including honeybees, bumble bees, carpenter bees, Habropoda laboriosa, and a collection of species they termed small native bees.

Shelley Rogers, a NCSU master’s student (now graduated), Burrack, and other collaborators surveyed local bee populations and measured the pollination of blueberry flowers visited by multiple bees (i.e., “open-pollinated”) and flowers pollinated via a single bee visit. They found that bee richness—the number of species present—was a better predictor of pollination than bee abundance.

“What we’ve been able to demonstrate, Burrack says, is that different bees do different things; that’s the core of how biodiversity benefits yield.”

So, for example, while honeybees prefer calm, sunny weather before they venture into the fields, native species are more tolerant of the cool, cloudy, windy days likely to prevail in early spring when blueberry plants bloom.

Some species groups are more efficient pollinators than others, producing, on a single-visit basis, a greater number of seeds—the “ultimate measure of pollination because that’s what will make a bigger blueberry,” Burrack says. Some species visit more flowers or have greater flower fidelity, preferring one type of blossom above all others. And some are simply more plentiful. And although Burrack says it is difficult to prove, some species may also be more resistant to common bee stressors, such as the parasitic varroa mite, viruses, or pesticide exposure.

Says Burrack, “No bee is perfect in all categories—forages under any weather conditions, visits lots of flowers really quickly, is abundant, or pollinates a lot of seed.” However, large, multi-species bee communities can, “get to that perfect bee level” in aggregate.

Since the USDA figures that bees pollinate 75% of all fruits, nuts, and vegetables grown in the United States—a harvest worth $20 to 30 billion annually—there is vast potential to recruit the services of the country’s 4,000 native bee species.

Value of abandoned fields, woodlands

While the value of pollination may be obvious to a fruit farmer, diverse, interconnected communities of flora and fauna can provide other ecosystem services as well. J. Franklin Egan, an agroecologist and postdoc at the USDA-ARS, for example, points out a host of things native plants can do for farmers.

“Wild plants serve as the basis for insect services,” he says, including natural pest control. “Hedgerows and buffer strips can be enormously important in providing windbreaks, halting erosion, and filtering water. Natural or semi-natural plant communities sequester carbon and filter air.” They also provide habitat for wildlife of cultural, recreational, and economic value.

Far-sighted farmers with a broad systems perspective can reap the benefits of these services at minimal or no cost. Moreover, oftentimes measures to boost one ecosystem service will boost others as well.

Doug Landis, a Michigan State University scientist focused on insects and landscape ecology, says the easiest thing farmers can do to cultivate biodiversity and attendant ecosystem services is simply not to remove certain habitats.

“If they have lands that are not being actively managed—these could be wooded areas, abandoned fields, early successional habitat—rather than converting them into farmland, they may want to consider the value of retaining them.”

These lands, Landis says, “do have value, and many are providing resources for beneficial insects.” Continue reading...