When an Abundance of Wasps is NOT a Problem
Mike has a timely conversation with You Bet Your Garden producer Alexis Landis about the recent massive kill-off of bumblebees in Portland…
Alexis: Mike, I know you had a different topic planned for this week's Question, but the recent mass killing of bumblebees in Portland, Oregon has a lot of people really upset. What can you tell us about what happened?
Mike: As soon as I heard about this (from a listener), I called Rich Hatfield, an Endangered Species Conservation Biologist for the Xerces Society, a group dedicated to protecting pollinators and other invertebrates. Their headquarters is in Portland, where the incident took place. It happened on a Saturday, and when Rich and his co-workers came into the office on Monday morning, there were several phone messages waiting from concerned citizens who had tried to reach them over the weekend.
A: What were they saying?
M: That bees were literally falling out of the trees in a local parking lot. Rich went to the scene and found thousands of dead bees on the ground, with more still falling out of the trees.
A: What did he do?
M: He immediately called the Oregon Department of Agriculture, whose response, he says, was really impressive. They came out right away, saw the carnage, tested some dead bees, and quickly identified the pesticide that was responsible. The trees were then covered with netting to try and prevent more bees from reaching them. Rich praised the Ag department's response; they clearly took the situation very seriously—as they should; this massive kill-off is near important agricultural areas that rely on the pollination these bees provide. Or at least used to provide….
A: What kind of trees were involved? And what exactly happened?
M: The parking lot contains around 55 lindens, which Jeff Meyer's "The Tree Book" (Scribner; 2004) describes as "an excellent shade tree with unique heart-shaped leaves" and an abundance of fragrant flowers that open in June and "attract a large following of honeybees." Beekeepers love having these trees around. Rich from the Xerces Society told me that a Portland beekeeper says he gets an astounding 50 to 100 pounds of honey from the bloom of a single mature linden tree!
A: That's amazing—and these wonderful trees are in a parking lot?
M: Yes. It's very ironic. Rich said that before the spraying, the landscaping around this store had been very beneficial for local pollinators and beneficial insects.
A: So someone sprayed the trees…
M: A landscaper hired by the company that manages the property sprayed the trees because they supposedly had aphids. Large numbers of aphids can secrete a sticky black honeydew that, one supposes, people were concerned about dripping onto nearby cars. But the store where this happened said that no one had complained to them about anything like that…
A: It's a Target store, right?
M: Yes, but Rich says they're not to blame. They lease the property, and someone representing the company they lease it from is the one who ordered the spraying.
A: What did they use?
M: The worst thing possible—an insecticide known as "Safari" (Dinotefuran), which is one of these "neonicotinoids"; pesticides that have a nicotine-like effect on insects, essentially exciting them to death. This is the exact same class of chemicals that's been heavily implicated in the Colony Collapse Disorder that's devastating honeybee populations. The label clearly says that it's toxic to bees and shouldn't be sprayed on plants in bloom—and yet it was sprayed into trees that were obviously covered with flowers and bees.
A: That's terrible!
M: Rich called it "a horrific scene". Right now, the death toll is estimated to be around 50,000 bumblebees, most of which were a specific species called the yellow faced bumblebee. There were also dead ladybugs—which, of course, had been helping naturally control the aphids—and some honeybees on the ground. And a local beekeeper recently told Rich that his hives—which are located about a half mile away—don't look too good.
A: If the aphids were a problem, what should they have used?
M: My first choice would have been pressure washers! A classic study found that sharp streams of water were more effective at aphid control that actual pesticides. The water blasts the nasty little sap-suckers off the plants so effectively, you get a 90 to 95% knockdown.
A: That's what you've been telling our listeners for years; if you have aphids on your roses, get a nozzle that delivers a sharp stream of water…
M: …And just blast them off! Water is often the best pesticide of all; you just have to know how to use it. Insecticidal soap sprays are also effective against aphids, as are light horticultural oils—and if you apply these treatments at night, when bees aren't feeding, there won't be any collateral damage, as soap and oil are only deadly when they coat and suffocate the pest insect. There's no poison involved, so bees that show up the next day aren't in any danger.
A: So many pesticides are toxic to bees, and bees are so important to our survival. Do you think this might be a wake-up call that will make people think more about the dangers of pesticides?
M: I hope so. Otherwise 50,000 bumblebees just died in vain. And you know the classic line: "no bees; no food".
And here's an exclusive Gardens Alive! extra…
I also asked "Common Sense Pest Control" expert Bill Quarles of the BIRC what he thought about all this. Here's his (sad) reply:
"Dear Mike: When this story first started making the rounds on the IPM Network, no one could believe it. Dinotefuran (Safari) is labeled for use against aphids on ornamental trees. But the label also reads 'This product is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees are visiting the treatment area.'
"Dinotefuran is also a persistent pesticide. Its soil half-life is 138 days, so it will continue to kill the bees if they can get to the leaves and flowers. Dinotefuran is soluble in water, so they could conceivably pressure wash it off. But then the parking lot would be contaminated, and it might run off into streams. A sad, sad day."