In his research field, Zachary DeVries Urban entomologists have seen plenty of German cockroach infestations. Inevitably, when they enter homes infested with the spindly pests, they also see something else: insecticide sprays in cans and bottles that can be bought at basically any hardware or grocery store across the country. “We saw these products everywhere, we saw people using them, and yet we continued to see people continue to deal with these pests,” says DeVries, the assistant professor at the University of Kentucky. Popular Science.
The infestations continued because people weren’t using the sprays correctly, or maybe the products just didn’t work. Over the course of more than a decade of research into better understanding and eradicating cockroach infestations, DeVries began to wonder: “Do consumer bug sprays actually work?” New research from DeVries and his colleagues gives that question a resounding answer: no.
Common consumer insecticide sprays and aerosols are not effective against German cockroach infestations. the study Released on August 14th Journal of Economic Entomology. The findings have major implications for the management of one of the most insidious household pests, as well as the way pesticides are regulated and sold.
“This is really important work.” Michael Scharfis a retired urban entomologist and insect toxicologist who studied insecticide resistance in cockroaches for many years at the University of Florida and Purdue University.German cockroach Evolved alongside human settlements thousand yearsWhile other cockroach species, such as the larger American cockroach, can invade indoor spaces and become a nuisance, the German cockroach lives exclusively in human buildings and is the most prolific and troublesome household pest. Not only are they unsightly and annoying, A major public health concern Cockroaches live in cities around the world. Their saliva, droppings and body parts can cause allergies and respiratory diseases, and these insects Key drivers Unbalanced High rates of asthma It was observed in children living in urban areas and in public housing.
Bankby
In past studies, Repeatedly proven The majority of the free-ranging German cockroach population Advanced Resistance Pyrethroid insecticides Most commonly seen Consumer pest control products contain a number of sprays that claim to kill cockroaches. But the new study is notable because it actually evaluated commercial sprays and thoroughly assessed their residual effects under a variety of exposure conditions, Scharf says. “Typically, studies are paid for by the manufacturers,” he notes, and as such, publications that portray specific products negatively are rare. But this new study is different: it was funded by the federal Department of Housing and Urban Development, and it names the specific sprays it analyzed, Scharf says. That means the findings can be used to directly advise households struggling with cockroach infestations.
DeVries and his co-authors tested four consumer products for various applications — Raid Ant & Roach Killer 26, Hot Shot Ant, Roach & Spider Killer, Ortho Home Defense Insect Killer for Indoor & Perimeter, and Spectracide Bug Stop Home Barrier — and found that while all the sprays easily killed susceptible lab strains of German cockroaches that don’t carry insecticide resistance genes, they were completely ineffective at controlling infestations in field-collected insects from three different free-living populations.
Naturally, spraying directly on insects The usual University of Florida entomologist and lead author of the study, Jonnalyn Gordon, said the insecticides don’t kill their targets. But worryingly, some insects survived direct application of certain sprays. And, crucially, all four products had weak residual effects, meaning cockroaches exposed to surfaces sprayed with the insecticide typically survived. Residual effects — an insecticide’s ability to kill insects even when you’re not looking directly at them — are key to pest control, Gordon said.
“It’s nearly impossible to spray insecticides directly on every cockroach in your home,” she explains. Most cockroaches hide and can’t always be reached. For a product to be effective, it has to kill any roaches it comes into contact with during its journey and hang on for a long time. Gordon and DeVries’ research shows that these sprays don’t do that.
“If you find a bug that you can spray, you can hit it with a hammer,” says DeVries. In short, there’s no benefit to either using timely bug spray or wearing shoes.
Entomologists sprayed each product on three different common household materials: stainless steel, ceramic tile, and painted drywall. They then exposed 10 cockroaches to each surface/spray combination for 30 minutes, after which they moved the cockroaches to an insecticide-free environment. After 24 hours, fewer than a quarter of the cockroaches were dead in all test conditions. Painted drywall, the most porous surface, had the least deadly outcomes. But even steel and tile had instances where not a single cockroach died after 30 minutes of insecticide exposure in the experimental scenario. This is despite marketing materials for all four sprays touting long-term residual efficacy and pest protection lasting from four weeks to 12 months.
The goal of the experiment was to mimic the short-term exposure that cockroaches might encounter in a house sprayed with pesticides, Gordon says, but this is an idealized exposure scenario that likely doesn’t occur in most homes. Previous researchGordon points out that German cockroaches don’t stay on surfaces coated with pyrethroids for long: The chemicals irritate the insects, so they avoid them. In most cases, a cockroach probably won’t crawl around in the insecticide for more than 30 minutes.
In additional tests, the researchers tried to find out how long that would last. Probably. They looked at how long it took for the insecticides to kill 100% of the cockroaches. They found that cockroaches needed to remain in contact with the treated surface for anywhere between eight and 24 hours to die, down to the last one. “That’s a long time,” DeVries said, noting that it’s “highly unlikely” that such a situation would occur outside of a laboratory environment. “Everything we tested was totally ineffective. It didn’t kill the roaches,” he added.
Disadvantages of insecticides
Moreover, they carry potential risks when used inside the home. Compared to other insecticides, pyrethroids are Relatively safe When used as directed, pyrethroids are non-toxic and have not been associated with an increased risk of cancer, for example. However, long-term or repeated exposure can still lead to health problems. One study showed that exposure to pyrethroids during childhood: May have adverse effects Cognitive development, another related pyrethroid level Teenage Hearing LossOn the other hand, another study showed that high levels of pyrethroid metabolites Increased risk of death Deaths from all causes and deaths from heart disease. In one case study, Examples of facial paralysis Infants exposed to pyrethroids. Misuse, such as overuse, ingestion, or inhalation, poses more immediate risks.
“In our field, we always have cost-benefit discussions,” DeVries says. While pesticides are almost always necessary to deal with serious insect infestations, the risks must be considered and balanced with the benefits, he explains. “If you put pesticides in your home, the risks may be very small, but the benefits still have to outweigh the potential harm. In this case, there are no risks, just costs.”
Popular Science The manufacturers of each of the four products tested were contacted for comment, but Scotts Miracle-Gro, the parent company of Ortho, and Spectrum Brands, the parent company of Spectracide and Hot Shot, did not respond as of press time. Raid had not issued a statement as of publication time.
Regulatory changes
In the United States, all consumer insecticides are regulated by the Environmental Protection Agency, which issues guidelines for testing and labeling products. All of the sprays studied met EPA requirements to be marketed as effective against cockroaches. However, the new study highlights that the EPA allows the approval of insecticides for cockroach control only after testing on susceptible laboratory strains of cockroaches that have not developed resistance to pyrethroids.
“This is a flaw in testing,” Gordon says. “If resistant populations were included as a testing requirement for product registration, it would raise standards across the board,” she adds. She and DeVries hope that their study will help prompt regulatory changes similar to those currently being made. It’s already happened For bedbug pesticides, the agency requires companies to report test results on the strains of insects they collect in the field.
Alternative attacks
The repeated purchase of ineffective products, combined with the difficulty of combating cockroach infestations in apartment buildings, leads many people to feel like cockroaches are an unsolvable problem. “It can create a situation of hopelessness,” Scharf said.
But cockroach infestations are not insurmountable, and there are things people can do. Taking out the trash daily, cleaning up and safely storing pet food, sealing entry points, and fixing water leaks are great early steps to minimize resources available to cockroaches, Scharf says. Consumer insecticide products are also worth trying; avoid “bug sprays” and full-release sprayers. Doesn’t workDeVries points out that insecticide resistance is high, which comes with a significant risk of pesticide exposure. A better strategy is to buy gels or other bait products that are meant to be ingested by pests. These target the delivery of the insecticide, minimize the risk of exposure to humans and pets, and are generally more effective, DeVries points out. If one bait stops working, he recommends trying another to combat insecticide resistance.
German cockroaches are a uniquely adaptable species. As an evolutionary weapon in their arsenal to evade pesticides, they’ve evolved “Swiss Army” detoxifying enzymes that can break down multiple types of pesticides, Scharf says. With enough time and exposure, cockroach populations are likely to become substantially resistant to the pesticides humans apply. That’s where the experts come in. Integrated pest management and the careful rotation of different pesticide treatments, an industry-wide practice, DeVries notes, can prevent resistance from building up and eradicate infestations altogether. In most states, homeowners and building managers can: Legally required Ensuring a pest-free environment often requires hiring a professional pest control service.
We’re locked in a millennium-long arms race with the German cockroach. Luckily, a winning strategy exists, but it doesn’t come in a spray can.
