COLUMNS


Are Native Pollinators a Reasonable Alternative to Honeybees?

By Sally Colby




The blue orchard bee, Osmia lignaria, shows potential as an alternative pollinator for tree fruits.
Photo by Scott Bauer, courtesy of USDA-ARS.

The decline of honeybees isn't new. Over the years, orchardists have noticed fewer bees and inefficient pollination, and they are looking for answers. Mace Vaughan, a pollinator conservation specialist with the Xerces Society, says that rather than relying on honeybees, encouraging wild bees may be the way to achieve efficient pollination for fruit crops.

A new national grant that involves colleges and Universities across the nation focuses on integrated crop pollination. "Michigan State, Penn State, Oregon State and the University of California are looking at the concept of ICP - the combined use of different pollinator species, habitat augmentation and management practices to provide reliable, economical and sustainable pollination for orchards and other crops," said Vaughan. This five-year study will examine alternative pollinators such as Osmia species, along with habitat enhancement.

"The reason we're looking at other bees is because of colony collapse disorder [CCD]," said Dr. David Biddinger, a Penn State tree fruit entomologist who has conducted extensive research in the orchard industry. "I've looked at integrating reduced-risk pesticides through the RAMP [Risk Avoidance Management Program], and I'm looking at conserving beneficial insects. It always amazes people that only one out of about 100 insects in the orchard is actually a pest - a lot of them are potentially beneficial."



This 20-year-old colony of wild honeybees in an old house was removed and relocated by experienced beekeepers who realize the value of preserving wild colonies.
Photo by Sally Colby.

Biddinger says that through RAMP, he documented the effects of pesticides on pollinators. "Most people don't realize that there are 22,000 kinds of bees in the world," he said, adding that most people think that only honeybees and bumblebees are important pollinators. "There were a lot more bees long before the honeybee was introduced from Europe, and they've been doing the job pretty well." Biddinger doesn't discount the value of honeybees, but says that they require a high level of management and probably aren't the most efficient pollinators.

"The reason we're looking at solitary bees and other alternative pollinators is because of CCD, which hit everybody in 2006," said Biddinger. "The problem with relying on honeybees is that they can carry disease, such as fire blight, from orchard to orchard. While honeybees will travel long distances, the native, solitary bees tend to work within a more defined area. They're excellent foragers, but they tend to go down the rows instead of across the rows."

Biddinger says that even though acreage for crops has increased, honeybee colonies have been declining since World War II. Feral honeybees are also in decline, and although some are coming back, they can't be relied on. One problem is the practice of pushing out brush at orchard edges, which reduces refuge for both honeybees and native pollinators. Solitary bees are a much better choice for some crops, especially stone fruits, although some of the viruses that are contributing to the decline of honeybees may also affect native pollinators.

"Many growers are not using honeybees at all," said Biddinger. "Half of the apple growers, especially smaller growers, are not using honeybees at all. By diversifying the types of pollinators, we reduce the chance that we will be without pollinators."

There are numerous theories to explain CCD, but Biddinger says that it comes down to a combination of factors, all compounded by stress. Bees are stressed when they're put on large trucks and hauled across the country, when they're being fed corn syrup for nutrition, and when they're harboring viruses and mites.

Biddinger says that extensive research shows that neonicotinoids aren't totally responsible for CCD; neonicotinoids are applied at lower rates in apple orchards than in landscape applications, and are used just once or twice in a season.

When it comes to alternative pollinators, Osmia species have gained significant attention. "They don't sting, they're used all over the world, and there are various species," said Biddinger. "The blue orchard bee (Osmia lignaria) is being developed for almonds on the West Coast - it does well under dry conditions."

Biddinger referenced work with Osmia cornifrons, the Japanese orchard bee (JOB), which is used for apple pollination in most of Japan. The JOB is popular in Europe for several reasons; honeybees are not allowed because of fire blight, and streptomycin can't be used.

"This bee has been used in Japan for over 80 years for almost all of the apple pollination," said Biddinger. "They were brought to the U.S. about 25 years ago by USDA-ARS and have become established in orchards. They like diversified farms - they come out a couple weeks before apple bloom and move through apricots, peaches and cherries, then peak during apple bloom."

Unlike honeybees, Osmia produce just one generation and will stay in a concentrated area within the orchard. "When you put a honeybee hive in the middle of an apple block, about 10 to 20 percent of the pollen is actually from apples," said Biddinger. "They'll bring in pesticides from outside the orchard, because they're generalists. When you put Osmia in an orchard, at least 90 percent of the pollen is from that crop, whether it's pear, apple or peaches. Japanese research showed that a single Osmia does the work of up to 100 honeybees. Each visit results in complete pollination - they carry pollen on their entire body."

The Japanese proved that a honeybee sets only 50 apple blossoms in one day, while an Osmia bee visits over 2,500 apple blossoms in a single day. "They're little workhorses," said Biddinger. "It's like watching hummingbirds on caffeine - they hit 15 flowers in a minute." Utah research showed that Osmia can double the yield of cherries and set more seeds in fruit.

Although some research is aimed at establishing mass production of Osmia, much of the current work is aimed at preserving wild Osmia populations.

The author is a frequent contributor and freelance writer who farms and raises Great Pyrenees in south-central Pennsylvania. Comment or question? Visit www.farmingforumsite.com and join in the discussions.