But Does It Work?
By Frank Carini / ecoRI News columnist
Mosquito Mary, Mosquito Mike, and Mosquito
Joe (I’ve yet to see a Mosquito Frank) are making bank killing insects we
depend on to pollinate the food we eat and the flowers we pick. The poisons
they spray don’t target just mosquitos and ticks; they can kill
indiscriminately, especially when applied improperly.
Market research shows the global mosquito
control market was valued at $793 million in 2021 and is projected to reach
$1.4 billion by 2027, according to a Georgia-based pest control franchise.
“Opening a mosquito-spraying business or adding it to your already established venture will let you join this growing market,” according to a GrassRoots’ promotional webpage. “Starting a mosquito-spraying business or adding a mosquito-spraying service to your existing business is a boon to both you and your customers.”
It’s not that for the natural world.
The ailments spread by ticks and mosquitos
— Lyme disease, anaplasmosis, babesiosis, powassan, ehrlichiosis, West Nile
virus, eastern equine encephalitis, and the Zika virus — can have grave heath
impacts and should be taken seriously, but so too should our relentless
spraying of poisons and our persistent use of toxic chemicals, such as per- and
polyfluorinated substances (PFAS). These human-made concoctions saturate the
planet, mixing with each other in ways we don’t understand.
The poisons used to kill ticks and
mosquitos are part of a cocktail of chemical pollution, including lawn-care pesticides
and fertilizers, that threaten the stability of global ecosystems upon which
humanity depends, according to a 2022 study.
And does the dumping of all this poison
even work? It depends on who is doing the applying and what is being sprayed,
when and where.
In mid-May, my wife and I received a
two-sided, glossy flier in the mail calling on us to “Stake your claim on
outdoor fun!”
The Mosquito Squad mailer said its
seasonally recurring service helps keep “those pesky mosquitoes and ticks away,
so you can spend more time enjoying your backyard.” A “highly trained”
technician would treat our yard every 21 days. The first treatment would cost
$49.
Mosquito Squad of Rhode Island claims
its most popular mosquito control treatment eliminates up to 90% of the
mosquito population in your yard. It claims its bug-killing formula provides
immediate and continuous 21-day protection.
A few weeks later, we received a Mosquito
Joe mailer telling us to “make memories without mosquitoes, ticks, and fleas.”
It featured a photo of a small dog, wearing a green Mosquito Joe shirt, flanked
by a young girl giving the smiling pet a kiss and a younger boy providing a
hug. They are all sitting on the lawn.
The glossy, two-sided flier claimed its
“customized treatments are built for your unique yard and will keep your family
and pets itch-free for 21 days.” The first treatment would cost $49.
Mosquito Shield, a
residential mosquito control company, says it, on average, sprays every 10 to
17 days, “a proven and effective approach that has us spraying 4-6 more times
than the industry average.”
In 2020, the 50-year-old lawn-care
franchise Weed Man expanded its service offerings and launched Mosquito
Hero.
Rhode Island’s foremost authority on ticks,
University of Rhode Island professor Thomas Mather, calls residential tick
control “kind of a Wild West show” filled with nonspecific answers about what
applicators are spraying and how often, and if natural control products even
work.
“People that use natural products don’t
really know if it works, as far as I’m concerned, because it’s not regulated,”
he said. “They don’t have to prove efficacy to say that they can do it.”
An acre test plot on the URI campus —
created to resemble a shady yard — is used by Mather and his student
researchers to test natural tick control products. He and his team have tested
nearly two dozen commercially available products. These natural products have
shown limited success in killing ticks.
“They all advertise that they kill ticks.
But when we did them in a single spray compared to a single spray of synthetic
pyrethroids, most of them didn’t achieve a very high kill of blacklegged
ticks,” Mather said. “Now, some of them argue that’s why we go five times,
well, by the fifth time if you go every other week, nature has already kind of
killed those ticks off. So it looks good, right?”
Mather said these companies often prey on
what people don’t understand about ticks. He noted cedar oil and garlic oil
don’t kill or keep ticks away.
“I know, as a tick biologist, you only have
to kill ticks once and then, you know, it’s not like mosquitoes that can fly
back in from outside. And if you kill the nymphs in the summer, they won’t be
there to turn into adults in the fall,” said Mather, who serves as director of
URI’s Center for Vector-Borne Disease and
its TickEncounter Resource Center.
He said in the first year a homeowner may
want to have a few treatments applied, but once you get started there is no
need to have multiple sprayings every year.
In fact, when it comes to what works best
in backyards to control ticks, it’s likely guesswork. Few if any of the
businesses that spray for ticks check first to see if any parasitic arachnids
are even present, if there are what species are they, and where are they on the
property, according to Mather, whose research focus is on tick ecology,
area-wide tick control strategies, tick-bite protection, and tickborne disease
prevention.
To find out what works and what doesn’t,
URI scientists, including Mather, are looking for Rhode
Island homeowners who will be doing some form of residential tick control this
spring or next — be it sprays, granules, or host-targeted control
professionally applied or do-it-yourself. The goal of the multiyear project is
to determine if the tick control homeowners apply is helping reduce the number
of ticks in their yards.
The home visits are held in June, the peak
season for tiny nymphal blacklegged ticks. Blacklegged ticks, or deer ticks,
are the carries of Lyme disease. Researchers will make property visits to check
for ticks — all species known for the area — and they will test those ticks for
pathogens. Investigators will also try to recruit neighbors during the visits
to compare treated and untreated yards in the neighborhood.
The URI project is part of partnership of
seven regional colleges and universities that has launched Project
ITCH (Is Tick Control Helping?) to determine best practices for
residential tick control in the six New England states.
The chemicals most often sprayed to kill
mosquitoes and ticks are synthetic poisons known as pyrethroids. More than
1,000 pyrethroids have been developed, but less than a dozen of them are
currently used in the United States, according to the Centers for Disease
Control and Prevention (CDC).
Mather has had pyrethroids sprayed on his
property to control ticks since he moved to Rhode Island in the mid-1980s.
Some companies do offer natural mosquito- and tick-killing treatments using a naturally occurring mixture of chemicals found in certain chrysanthemum flowers. Pyrethrum was first recognized as having insecticidal properties circa 1800 in Asia and was used to kill ticks, fleas, and mosquitos.
Six individual chemicals have active insecticidal
properties in the pyrethrum extract, and these compounds are called
pyrethrins. Pyrethrins can be
released naturally from chrysanthemum flowers, but these releases are tiny
compared with the amounts used as commercial insecticides.
Mosquito and tick killing products that are
organic will feature an Organic Materials Review Institute (OMRI)
seal. The Eugene, Ore.-based international nonprofit assures the suitability of
products for certified organic production, handling, and processing.
Pyrethroids — the
first one, allethrin, which is highly toxic to fish and aquatic invertebrates,
was invented in 1949 by the U.S. Department of Agriculture — are manufactured
chemicals that are similar in structure to pyrethrins, but are often more toxic
to insects, and mammals, and last longer in the environment than pyrethrins.
Concentrated pyrethrins and pyrethroids are
usually mixed with carriers or solvents to produce a commercial-grade
formulated product, according to the CDC. These formulated products contain
inert ingredients that can increase their toxicity.
By law, the active ingredient must be
identified by name on the pesticide label and its percentage must be provided.
Nonactive ingredients — sometimes called inert ingredients — don’t need to be
identified by name, just the percentage of nonactive ingredients must be
specified, so it can be difficult to determine what other chemicals are
included in the final formulated product.
In air, all six of the pyrethrins and many
of the pyrethroids are broken down or degraded rapidly by sunlight. Often, they
last only one or two days before being degraded, according to the CDC.
Steven Alm, a professor of entomology at
the University of Rhode Island, noted both synthetic pyrethroids and botanical
pyrethrins can be toxic to bees and other pollinators. They will kill whatever
insects they land on, he said.
They are both safe to pollinators once the
poison has dried and sunlight begins to break them down, so the number of
non-target species killed by spraying depends, to a large extent, on the
training and skill of the applicator.
Alm said if an applicator isn’t trained or
aware to avoid flowers, for instance, it could cause environmental harm,
especially to bees, lady beetles, and other beneficial insects.
Before any pesticide product the
Environmental Protection Agency hasn’t exempted from registration requirements
can be sold or distributed, the federal agency performs a scientific assessment that
results in a registration decision. Under this review, EPA evaluates the
product’s active ingredient(s), other constituent substances, including inert
ingredients, and the proposed use to ensure that, when the product is used
according to labeled directions, no unreasonable adverse effects on human
health or the environment will occur.
Once an EPA registration has been granted,
applicants then need to comply with the individual registration requirements
imposed by the states in which they wish to market their product.
The Rhode Island Department of
Environmental Management requires certification for commercial
applicators. The agency also used to require formal training, but that is now
optional. DEM does require that commercial applicators pass an examination,
which is based on federal regulations regarding
the types of pesticides they will be using.
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.
When DEM originally created the state’s
pesticide safety program in the late 1970s, training was required. But about
seven years ago someone challenged the requirement, and after reviewing the
matter, state officials found it to be unenforceable because there was no
statutory basis for the agency to require training, according to Michael
Healey, DEM’s chief public affairs officer.
Alm has noted this lack of training is
concerning.
Mather noted effective spraying for ticks
should be concentrated along a lawn’s edge, where leaf litter has collected. He
said ticks prefer moist, shady areas, like under ground-cover plants and around
stone walls and woodpiles, not sun-drenched lawns. Spraying flowers for ticks
is useless and harmful, he added.
Spraying leaf litter, however, can also
prove fatal for beneficial insects, especially decomposers such as beetles,
ants, and earwigs.
Mosquito and tick spraying typically
happens during business hours, say, 8 a.m. to 4 p.m., in daylight when
pollinators are active and most mosquitoes are resting.
“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 and it potentially could be
killing any number of beneficial insects that are in your yard, including bees,
butterflies, beneficial wasps, many insects that are actually eating and
killing pests in your yard,” Aimee Code, pesticide program director for the
Portland, Ore.-based Xerces Society for Invertebrate Conservation, told ecoRI News in 2021.
She noted another shortcoming of the
chemical approach is that when it comes to mosquitoes they are mobile, flying
into yards that have been sprayed and replacing those insects that were killed.
“Just because you’re spraying your yard,
mosquitoes can still move in after that chemical settles out and they’re going
to still bother you,” Code said. “It’s a very short-term, shortsighted fix.”
Alm said one of the best ways to control a
mosquito population in your yard is to make sure there is no standing water in
garden pots or in a decorative wheelbarrow. A bird bath or a rain barrel
without netting also offer mosquitos a place to reproduce.
Frank Carini can be reached
at frank@ecori.org. His opinions don’t reflect those of ecoRI News.