 of testing laboratories, but advertisements from companies that promise to eliminate them. Lawn-care companies have entered the lucrative business of mosquito control, and many other companies specialize in spraying for mosquitoes and ticks.
Some companies offer “all natural” yard treatments, but the chemicals most often used to kill mosquitoes are synthetic chemicals known as pyrethroids, not to be confused with pyrethrins, which are derived from a species of chrysanthemum.
Steven Alm, a professor of entomology at the University of Rhode Island, said pyrethroids will kill whatever insects they land on. A team of graduate students, led by Alm, recently found a single American bumblebee in Rhode Island — after about a decade of one not being observed here — but are keeping the location secret.
“Some of these mosquito products, for example, like the pyrethroids, yeah, if you hit the bees with them, and other beneficial insects, they’re going to be toxic to those as well,” he said.
Pyrethroids are safe to pollinators once the spray has dried and sunlight begins to break them down, so the number of non-target species killed by yard-spraying depends, to a large extent, on the skill and training of the applicator.
“If you’re not trained to avoid the flowers, for example, it could do some harm, especially to bees and parasitic wasps and lady beetles and things like that,” Alm said.
DEM requires certification for commercial applicators, but the agency also used to require formal training, which, DEM spokesperson Michael Healey said, is now optional.
“Since the inception of the pesticide safety program in the late 1970s, DEM did require training as a prerequisite for testing,” he said, “… someone challenged the requirement about five years ago … at which time DEM reviewed it and found it to be unenforceable because there was no statutory basis for us to require training. Since then, training has been voluntary.”
Alm said the lack of training is concerning.
“You know, you get these people that have not had training with pesticides at all to just go right out there — just hand them a book to study without any interaction with anybody,” Alm said. “I don’t think that’s the way to go.”
Spraying for mosquitoes and ticks and dousing lands with pesticides and herbicides isn’t limited to private yards. From 2010 to 2016, the Rhode Island Department of Transportation applied at least 43,959 gallons of herbicide to public lands across the state.
Pesticides are also applied at state parks, to the Statehouse grounds, and on other state-managed lands. Each of Rhode Island’s 39 cities and towns also apply poisons to eliminate unwanted plants and insects from public property.
DEM does require that commercial applicators pass an examination, which is based on federal regulations regarding the types of pesticides they will be using.
Healey said the state agency does require testing to demonstrate practical knowledge in the specific areas as outlined in federal law. He noted that from Oct. 1, 2020 to Sept. 30 of this year DEM administered 465 exams, of which 50 were retakes. Of the 415 first-attempt exams, 294 passed and 121 failed, for a success rate of 71 percent.
To maintain state certification, DEM requires private applicators take six hours of recertification training every five years. Commercial applicators must take eight hours of recertification training every five years.
A “shortsighted fix”
Mosquito spraying usually takes place during business hours, in other words, in daylight, when pollinators are active and most mosquitoes are not flying, but resting.
Aimee Code, pesticide program director for the Portland, Ore.-based Xerces Society for Invertebrate Conservation, noted yard spraying often misses the intended targets and kills beneficial species.
“There are some mosquitoes that are out during the day, but definitely, the vast majority of the chemical that’s being sprayed in your yard is not touching the mosquito — it’s not doing what it was meant to do — it’s just contaminating your yard,” she said, “and it potentially could be killing