Parting the broad, fan-like leaves of one of the 420 Gladiator pumpkin plants spreading over the sun-baked field, Kimberly Stoner found what she was looking for.
“Oh, yes, there’s a female flower,” said Stoner, associate scientist at the Connecticut Agricultural Experiment Station, pointing out the distinguishing miniature fruit structure at the base of the flower, sterile until fertilized with male pollen. “Each plant will have male and female flowers, and usually the males emerge first. But pumpkins are absolutely dependent on bees for pollination.”
The quarter-acre field, planted in early June, is part of the research Stoner is leading to better understand the critical relationship between pumpkins and their squash-family kin and bees, without which there would no jack-o-lanterns, no pumpkin pie and no butternut squash at Thanksgiving.
Looking At Pesticides
A multifaceted, federally-funded project, the research is intended to trace whether pesticides commonly used on pumpkins and squash are showing up in bee pollen, to add to emerging science on the causes of bee colony collapse, which has been plaguing agriculture for the past half-dozen years. The project will also compare productivity from fields using different techniques to attract pollinators, and which types of wild bees share the fields with the managed honeybee hives.
Stoner stressed the importance of the wild bees in their research. There are two species of wild bees – a type of bumble bee and a squash bee – that show up on their own in squash fields, Stoner said. Through her research and other studies, she has determined that those wild bees do about 80 percent of the pollination in the squash fields.
“Practically nobody has looked at pathogens of squash bees, so it’s all new,” said Stoner. U.S. Department of Agriculture-funded research is part of the Specialty Crop Research Initiative also supporting studies of cranberries in Massachusetts, blueberries in Maine and apples in New York state.
Earlier this month, Stoner and Amelia Tatarian, seasonal research associate, visited the experiment station’s research farm off Shelton Road in Griswold to size up the pumpkin plants’ growth and, based on the numbers of male and female flower buds, determine when the bees are likely to arrive.
“I’ll probably be back in a week,” said Stoner, who is keeping tabs on similar plots in Hamden and Windsor, as well as at 20 commercial farm fields around the state.
As Stoner and Tatarian checked each plant, tallying their findings, some 125,000 honey bees buzzed around hives in a shady spot several fields away. The hives had been brought to the farm a few days earlier by Mark Creighton, state apiary inspector. The bees are spending their days pollinating wildflowers around the farm until the pumpkin flowers start opening.
“Bees are very specific,” Creighton said, crouching beside one of the hives to watch a bee fly into the opening, its underside bright with white pollen, after getting clearance from the “guard bees” hovering outside the hive. “If they decide they’re going to pollinate squash, they’ll stay until it’s all done. That’s how they’ve evolved.”
“If we didn’t have honey bees as pollinators we wouldn’t have a lot of the crops that we take for granted, like strawberries and peaches, apples and pumpkins,” he said. “Most people don’t realize how much we rely on these little miracle workers.”
Last winter, he said, more than one-third of the state’s commercial bee population died, most likely from a convergence of stressors including invasive mites, infections and pesticide exposures, forcing orchard owners and other farmers to hire out-of-state beekeepers to truck their hives into the state for pollination season. Like tiny migrant workers with wings, honeybees are unique among other pollinators – including other insects, birds and bats – for their ability to be moved from place to place when people need them.
“This was the first time we’ve had to bring bees in from out of state to do some of the pollination,” Creighton said.
When the pumpkins were planted, an insecticide called Imidacloprid was applied to the soil around the roots. As the plants grow, they are absorbing the insecticide so that anything that eats the leaves and stems also ingests the chemical, and dies. Sold in hardware stores for home use under the brand name GrubEx, the insecticide has been on the market for about 20 years and is now one of the most widely used in the world, Stoner said. It is a particularly potent protection against highly destructive squash beetles.
Not So Benign
Imidacloprid, Stoner added, was first developed as an alternative to organophosphate pesticides. After concerns about toxic exposures of workers applying those chemicals directly on the plants, Imidacloprid looked like a benign antidote, a “systemic” pesticide that could safely be applied to the soil without harming humans.
But it turned out that bees, when they gather pollen and nectar from the squash flowers, also end up ingesting some of the insecticide, Stoner said. While it may not kill them immediately, Stoner said, there is now concern that it is having cumulative effects that, in combination with other stressors, are proving lethal. In the European Union, she noted, it has been banned for some specific uses.
Some facets of this project will rely on old-fashioned field work, with workers deployed into the fields throughout the season to track and record the types of bees visiting the flowers at various times, and the size, number and weight of the fruits.
“I’m going to tell the summer workers that they need to make up maps now showing where each of the plants are,” Stoner told Durgy. True to their reputation, Durgy said, the pumpkin plants would soon start spreading well beyond their orderly rows with long, intertwining vines that would make it hard to distinguish where one plant begins and the next one ends.
The pesticide research part of the project, however, will involve some more complex techniques. Pollen from the bees will have to be tested and analyzed in a lab for traces of pesticide. To collect the pollen, Creighton will attach a kind of gate on the front door of each bee hive. As the bees try to reenter, they will end up depositing half of the pollen they’ve gathered into a collection basket.
“I’m going to put a pollen trap on the first hive in the next day or so,” Creighton told Stoner.
A Courant staff report was added to this story.