Aerial spraying for mosquitoes Saturday, July 11, may also have taken a toll on beneficial insects, according to Clint Otto, a resident of Jamestown.
Otto is a researcher studying bees at Northern Prairie Wildlife Research Center although that research does not include the effects of insecticides on the insects. He said he based his comments and concerns strictly as a private citizen based on observations he made in his backyard shortly after the area was sprayed with permethrin from an aircraft.
"I knew the aerial application would impact the bee population," he said. "We went out after about a half hour. We could hear buzzing in the grass, not flying insects, presumably responding to the chemicals."
Otto checked the grass and captured several native bees, not commercial honey bees, that were "spasming" in the grass.
Dawn DeVillers, vector control officer for Jamestown, said the insecticide and the method used to apply it should have prevented damage to bees.
"The application rate used shouldn't have affected bees," she said.
DeVillers said the chemical used in Jamestown is approved for this type of application and used in many communities in the region.
Matt Solensky lives next door to Otto and is also a researcher at Northern Plains Wildlife Research Center. What he described as a "feral colony" of honey bees had taken up residence in hives he was storing in his backyard.
"About 15 or 20 minutes after the plane went over we went out," he said. "We were seeing honey bees on the ground squirming."
Solensky estimated two to three dozen honey bees died. He said those bees were probably outside the hive at the time of the spraying. Bees inside the hive were not affected and the hive was not destroyed, he said.
"I think (spraying) later at night would be better for at least the honey bees," he said, noting the bees return to the hive at night.
DeVillers said applications of insecticide are planned for the late evening to allow most bees to return to the hive. Also, aerial applicators avoid spraying any location where honey bee hives are registered with the North Dakota Department of Agriculture.
Spraying later wouldn't necessarily help the wild or native bee population, Otto said.
Otto said there are about 4,000 species of native bees in the United States and several hundred are native to North Dakota.
"A lot of bees are solitary and get together only to mate," he said. "They stay alone the rest of the time and aren't in hives."
Otto said both native and honey bee populations are important for pollinating crops. Statistically, the honey bee population has declined about 35% in recent years with a notable decline in native bees also seen, he said.
Human health concerns for diseases spread by mosquitoes are a concern, Otto said.
If mosquito numbers increase, another aerial application of insecticide would be considered, DeVillers said.
"We need to be aware of the unintended consequences," Otto said.