Hot News

1.15.2008

By SEAN CLOUGHERTY
Associate Editor

HARRINGTON, Del. — Native bees may do more pollination than we give them credit for and by helping them thrive with plants and habitat, they could do more, taking some of the burden off over-stressed honeybees.
That was one of the overall messages at the pollination workshop at the Delaware State Fairgrounds last week, part of Delaware Agriculture Week.
“The stars of this show are bees — not only honey bees but other native pollinator bees,” said Faith Kuehn, plant industries administrator for the Delaware Department of Agriculture, who led off the presentations.
Speakers discussed several different species of native bees and ways to keep them working on the farm.
Native bees are responsible for about 20 percent of the pollination in an average field, said Mike Embrey, University of Maryland Extension apiculturist.
In other parts of the world, coffee in Indonesia for example, native bees take care of nearly all the pollination. In her study of small watermelon fields in New Jersey, Rachael Winfree, a researcher at Princeton University, found that native bees accounted for 91 percent of the pollination in 2006 and 88 percent in 2007.
She said that some growers relied only on native pollinators and most of the fields were less than three acres and close to a lot of natural vegetation where native bees usually nest.
“When you get into large fields and an extensive monoculture, you may find a different answer,” Winfree said.
While large growers may not feel comfortable relying solely on native bees to pollinate high value crops like watermelons and cucumbers, allowing more native bees to nest near the fields will have its benefits, experts said
“When there is a mixture of bees ... the crops fair better,” said Dewey Caron, University of Delaware Extension entomologist. “There’s something going on. One-plus-one is something more than two. What we need to do now is not become complacent” and encourage more native pollinators.
Bumble bees can carry larger pollen loads and since they are larger than honey bees it is easier for them to touch the flower’s parts to get pollen.
They are also more tolerant of bad weather than honeybees.
But bumble bees do not recruit more bees into pollinating like honeybees do, they form smaller colonies and have an annual life cycle, leaving only the queen to build a new colony the following year, according to Embrey.
He also said bumble bees also look for the plants where they can get the most nectar ,which may not always be the fruit or vegetable crop.
About 70 percent of native bees are ground nesters, Caron said, and that group includes species like squash bees, green bees and digger bees.
While many ground nesters are solitary bees, the squash bee groups together, making aggregate nests in the soil.
They are the “workhorse” of native pollinators, Caron said.
Roberta Glatz, a New York master beekeeper, said the squash bee only pollinates plants in the squash family — pumpkins, gourds and summer squash — and synchronizes its life cycle to that crop. She added the males cannot sting and the females rarely do, making it safe to check plants in the morning to get an idea of how many squash bees are working.
To encourage more ground nesters, Caron said to set aside areas around tree lines, sheds or buildings near fields that will grow vegetables and try not to disturb them with tillage or parking equipment there.
In 2006, the department began a sampling study of native bees, hoping to establish a baseline of the native species in the area and from there, research the species’ life history in Delaware.
By catching bees in cucumber, watermelon and pumpkin fields of about 30 growers and some natural areas, more than 6,500 bees and 80 different species have been recorded in the study — including six species that were not previously recorded in Delaware, according to Heather Harmon, department entomologist.
Harmon said plants like goldenrod and coneflower are known to attract native bees and pointed to a pollinator garden the plant industries team planted at the department headquarters in Dover, Del., as an example.
“It’s really a build-it-and-they-will come” situation, she said.