Willy Gunther wondered what city workers were up to as they sprayed trees near his home last week.
When they told him they were spraying for aphids, Gunther was immediately concerned about his bees.
A worker phoned his supervisor and then told Gunther the insecticidal soap spray they use would neither hurt his bees, which unlike aphids have a hard-body shell, nor the purity of the honey the bees make with nectar from the linden trees.
But his worries persisted, so Gunther phoned his beekeeping buddy and Vancouver Courier columnist Allen Garr, who contacted Simon Fraser University biological sciences professor and bee expert Mark Winston.
“When they’re spraying there I’m supposed to keep my bees locked up,” Gunther said. “But how can I lock the bees up? They’re not a dog where I can lock it up for a day or so. The bees are free. Especially with that heat there, they’re outside. They’re hanging out in the front of the boxes because it’s too hot.”
Gunther wondered whether improper spraying could be contributing to the global disappearance of bees.
“Bees, not just honey bees, but bumblebees, mason bees, other tiny little insects, butterflies, hummingbirds, they pollinate close to two-thirds of our food,” beekeeper Sarah Common told the Courier earlier this month. “And urban landscapes have traditionally erased the foraging and the habitat of those pollinating insects.”
Winston said insecticidal soap spray is “not particularly toxic,” so it wouldn’t spoil honey.
“It’s quite safe for mammals,” he said.
“And once it dries, it’s not harmful to bees,” Winston said. “But when it’s wet, if the bees encounter it, it could cause them some trouble because any soap on an insect will make it difficult for them to breathe.”
Winston said wet soap could pose a risk for “at least a couple of hours” in hot weather.
“I wouldn’t recommend spraying that during the day,” he added.
The city sprays between 7 a.m. and 3 p.m.
“It’s usually never a good idea to spray anything in bloom when the bees are around,” Winston said.
Gunther said the linden trees near his block were in full bloom.
Sara Couper, a communications coordinator for the city, said workers spray between 7 a.m. and 3 p.m. in an attempt to hit an area when fewer residents are home.
Letters are hand-delivered informing residents of the date and time of the spray and include contact information, should residents have concerns.
“We have in the past, at the request of residents, avoided spraying certain trees,” Couper said. “We’ll make every effort to avoid that area and to minimize any of the spray drift off the actual street trees.”
Gunther didn’t receive a letter because he lives around the corner from the street trees that were sprayed.
The City of Vancouver has managed aphids on street trees since 1995 using ladybug releases and soap sprays. The city estimates more than 15,000 street trees are infested with aphids, to a mild or severe extent, on a yearly basis.