By Nicole Montesano • Staff Writer • 

Insecticides pose a dire bee danger

But bumblebees perform crucially important work. And like other pollinators, they are at risk from multiple threats.

So many people were shocked when they found tens of thousands of dead and dying bumblebees in the parking lot of a Target store in Wilsonville in late June after a landscaping company sprayed blooming linden trees there with an insecticide carrying a warning about the danger posed to bees.

The Portland-based Xerces Society for Invertebrate Conservation estimated the mass poisoning, the largest ever documented, affected more than 300 wild bumblebee colonies.

While many of the dead bees were of a common species that is currently doing well — the yellow-faced bumblebee — the Xerces Society is worried that others may have been from the endangered Western bumblebee species.

Rich Hatfield, an endangered species conservation biologist for the society, said area beekeepers also reported losses from their honeybee hives. “The ODA is looking into that,” he said.

In the wake of the devastating bee kill, and another of lesser dimension in Hillsboro, the Oregon Department of Agriculture restricted the use of 18 pesticides containing the active ingredient dinotefuran while it continues its investigation.

In the Wilsonville case, the company said that parking lot trees were sprayed for aphids to minimize sticky discharge onto shoppers’ cars below. Insecticides from the same family are used on ornamental plantings, fields of turf and farm crops.

The Oregon State University Master Gardeners Program immediately sent a notice out to its members, warning them not to recommend products containing dinotefuran for home use.

Dinotefuran and other insecticides in the neonicotinoid class are systemic rather than topical. That means they are absorbed by plants and come to permeate every part of them.

They are also extremely long-lasting, Hatfield said. He said their toxic effects can linger for years.

In addition, they are water soluble, and are coming into extremely widespread use, both in agriculture and ornamental applications.

In a press release issued in late June, the Xerces Society quoted a leading authority on bee health, Dr. Marla Spivak of the University of Minnesota, as saying, “If the Oregon event is an indication of what is happening more widely, we will begin to see catastrophic threats to food security and the pollination of wild plants.”

Fuzzy and rounded, bumblebees are charming, friendly looking creatures that run counter to most bee stereotypes. They don’t swarm or produce harvestable amounts of honey, and they seldom sting, absent a direct threat.

What they do is help to keep the plant world humming. In the process, they pollinate many of the food plants humans depend on.

Like honeybee species, some bumblebee species are kept commercially. They are most often used to pollinate greenhouse-grown tomatoes, strawberries, peppers and blueberries.

But the greater importance lies with wild, native bumblebees, which play a critical role in keeping ecosystems healthy.

“Especially in northern latitudes and high elevations, bumblebees are crucially important pollinators,” Hatfield said.

Unlike honeybees, he said, “They have the ability to thermo-regulate, so they can fly in temperatures just above freezing. They fly when it’s cloudy out, or when it’s raining. So in northern climates like Oregon, for huckleberries and a lot of plants like that, they are essential pollinators. They are out there pollinating the plants that our songbirds and animals, bears, other mammals, eat.”

He said, “For people, they are also incredibly important pollinators. For cranberries, blueberries, raspberries, apples – all those spring-blooming plants that, when it’s cold and rainy here in Oregon, and honeybees can’t fly, bumblebees are out there doing some of that work.”

Although there are some 4,000 species of bees in the United States, some of which perform redundant tasks, “Diversity is essential,” Hatfield said. Nature creates redundancies so crucial tasks get performed even when problems develop in one species.

He said specialization is also an important consideration. Losing one species often means losing the one best suited for a particular kind of work, he said.

Not all bees pollinate in the same way. Bumblebees will grab a flower and shake it to release pollen, a tactic that works especially well for tomatoes.

“Maintaining the general biodiversity for us is food security,” Hatfield said. “One out of every three bites of food we eat comes from food pollinated by bees.”

The Xerces Society encourages people to create safe habitat for bumblebees and other pollinators.

“There are three really important things you can do,” Hatfield said. Those are providing nesting areas, providing early spring through late fall blooms and avoiding the use of pesticides.

Good early-blooming plants include crabapples and redbud, he said, while good late-blooming choices include goldenrod and milk thistle. Nesting options include bunch grasses, unmowed areas and artificial nest boxes.

Avoiding pesticides is crucial, Hatfield said.

In both the Wilsonville and Hillsboro cases, he said, workers said they sprayed to control aphids, which drop honeydew on cars. But Hatfield noted that honeydew is simply a solution of sugar water that can easily be rinsed off.

“The cost of losing pollinators far outweighs any value of controlling aphids on ornamental plants,” said Mace Vaughan, Pollinator Conservation Director at the Xerces Society.

Jennifer Hopwood, the lead author of the Xerces Society’s report on the risks of neonicotinoids to bees, echoed that. She urges consumers not to spray neonicotinoids on plants or buy plants that have already been sprayed.

“When buying garden plants, people should ask the store if insecticides have been used on them,” she said. “If the staff can’t tell you, I would shop somewhere else.”

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