Tag Archives: insecticide

Cockroaches may soon become unkillable due to pesticide immunity

Scientists have found that German cockroaches (Blattella germanica) are developing cross-resistance to different classes of insecticides. In other words, with each generation that survives the chemical onslaught, the roaches are becoming immume to the toxins that would have killed their ancestors. Soon enough, roaches may become nearly impossible to kill through chemical means.

A German cockroach feeds on insecticide. Credit: Purdue University.

It’s not just that the cockroaches are developing immunity to insecticide — what was shocking to witness was the rate at which cockroaches started developing this immunity. Sometimes, it was within a single generation.

“We didn’t have a clue that something like that could happen this fast,” said study co-author Michael Scharf, a professor and chair with the Department of Entomology at Purdue University in Indiana.

For their study, the researchers at Purdue tested the effectiveness of three different classes of insecticides sprayed onto roaches, which were let loose in apartment buildings in Danville, Illinois, and Indianapolis, Indiana, over a six-month period.

One group of roaches was sprayed with a single insecticide, a second population was exposed to two insecticide classes, and a third group was exposed to three insecticides in rotation (one per month for two-month cycles).

In order to track insecticide resistance across multiple generations, the researchers trapped live roaches in baby food jars and took them back to the lab.

The findings were concerning, with most roach populations either remaining stable or actually increasing. Surprisingly, the rotating pesticide trial was the most ineffective because it caused the most cross-resistance.

What happened was cockroach offspring would not only become resistant to a pesticide that their parents had encountered but also other classes of insecticides which hadn’t been encountered by previous generations.

The only successful experiment was the one that used a single pesticide. However, this occurred in a population of roaches that had almost no resistance to the toxin. In a subsequent experiment that introduced the pesticide to a population that had slightly higher resistance, the number of roaches actually increased — this time with a new generation of resistant survivors.

“If you have the ability to test the roaches first and pick an insecticide that has low resistance, that ups the odds,” Scharf said. “But even then, we had trouble controlling populations.”

The German cockroach is a remarkable survivor, beingly notoriously difficult to control. The problem lies in the fact that even a couple of individuals survive, they are quickly able to replenish the population and even return in stronger numbers. A single female can deliver up to 60 nymphs per birth and are even able to reproduce without males — what scientists term parthenogenetic reproduction or virgin births. Previously, a study found that it is equipped with large gene families responsible for the metabolization of toxic substances, including some chemicals found in insecticides.

The new findings reported in the journal Scientific Reports suggest insecticides will become increasingly ineffective at controlling roach populations. Instead, we’ll have to use a combination of alternative approaches, ranging from traps to improved sanitation.

“Some of these methods are more expensive than using only insecticides, but if those insecticides aren’t going to control or eliminate a population, you’re just throwing money away,” Scharf said. “Combining several methods will be the most effective way to eliminate cockroaches.”

German cockroach.

Bug bombs don’t kill the bugs, but they do expose you to pesticides

Bug bombs are really good — if you like having cockroaches for flatmates.

Orion insecticide.

Orion insecticide.
Image credits Tamorlan / Wikimedia.

New research from the North Carolina State University showed that total release foggers (commonly known as “bug bombs”) are ineffective at removing cockroaches from your home. The chemicals they release fail to reach the places that these insects tend to hang out in, such as the undersides of surfaces or inside cabinets.

Indiscriminate bombing

“There’s been a general assumption that bug bombs work to eliminate cockroaches indoors, but no one had conducted a formal assessment of their efficacy and any exposure risks,” said Zachary DeVries, an NC State postdoctoral researcher and the lead author of the study.

“We’ve done that simultaneously in this study.”

Besides not removing the majority of cockroaches, these devices also leave behind toxic residues — particularly in the center areas of floors and furniture. Cockroaches tend to avoid these areas, but they see heavy use by humans and pets.

The team tested four different commercially-available bug bombs that use various insecticide compounds in five apartment complexes. These complexes were chosen for their level of bug activity — all five had moderate to severe German cockroach (Blattella germanica) infestations. All the bombs used in the study contained pyrethroids, the team explains, a class of fast-acting insecticides. Some also contained other active substances, such as piperonyl butoxide, which prevents cockroaches’ bodies from metabolizing the insecticides.

German cockroach.

German cockroach, Blattella germanica.
Image credits Matt Bertone.

First, they estimated cockroach populations in 20 homes in these five complexes. Then, following the instructions on their labels to the letter, the team set up and set off the bombs. Cockroach populations were re-examined two weeks and one month after the bombs were used. Overall, these devices had no meaningful impact on the insects, the team finding no evidence of decline from their initial estimates.

“The bug-bomb products did absolutely nothing to control cockroach populations in these homes,” DeVries said.

The team also applied either commercially-available gel bait or a professional-grade gel bait in 10 additional homes. Gel bait is generally applied via a syringe to the areas where cockroaches hide. This bait was much more effective than the bug bombs both at the two- and four-week marks, the team notes, virtually eliminating cockroach populations in all of the 10 homes.

To help them better gauge the effectiveness of the bug bombs, the team placed roaches (some raised in the lab and others captured into the homes themselves) in cages on the floor and in upper cabinets of the homes involved in the study. The cages were greased so that the insects couldn’t escape. These cages were installed during the bug bomb testing phase of the study.

“The lab roaches, which are not hardy, had high mortality, as expected,” DeVries explains. “The roaches captured in the homes and then brought back, however, had far lower mortality rates than you would expect from direct exposure to bug bombs, confirming the ineffectiveness of these products when used for German cockroach control.”

Overall, then, the bug bombs had shown themselves ineffective in their intended role. With this in mind, the team set out to quantify their collateral effect — the risk of exposing people and pets to insecticides in their homes. The team swabbed floors, kitchen surfaces, walls, and cabinets in the homes prior to bug-bombing them. This preliminary analysis showed insecticide residue was already present in the homes used in the study, giving the team baseline concentrations to work with. These baseline levels can be explained by residents facing cockroach infestations — as was the case with the families involved in the study — using insecticides in an attempt to remove the pests. These residues were found in samples collected from the middle of floors and kitchen surfaces, DeVries explains, so the finding is “most disconcerting”.

The same areas were swabbed four to six hours after the bombs were deployed. The team reports that insecticide residue levels increased 600-fold on average across all horizontal surfaces. Swabbings performed one month after the study showed insecticide residue levels were still 34% higher than the baseline.

“Bug bombs are not killing cockroaches; they’re putting pesticides in places where the cockroaches aren’t; they’re not putting pesticides in places where cockroaches are and they’re increasing pesticide levels in the home,” DeVries said. “In a cost-benefit analysis, you’re getting all costs and no benefits.”

“This is of particular concern in low-income communities, where bug bombs are frequently used because professional pest control may be too expensive,” adds Coby Schal, Blanton J. Whitmire Distinguished Professor of Entomology at NC State and senior author of the paper.

Insecticides aren’t particularly healthy for you — by ‘particularly’ I mean ‘at all’. Pyrethroids, the same compounds used in this study, are preferred for household use due to their fast biodegradation/breakdown and relative low mammalian toxicity (except for cats) compared to other insecticides.  However, there is evidence that even pyrethroids have an adverse effect on the development of rats, causing behavioral changes that resemble Attention Deficit/Hyperactivity Disorders (ADHD) in humans. There have also been reported cases of anaphylactic shock after exposure to pyrethrum, although no link between pyrethroids and allergic reactions has so far been established in the scientific literature.

The paper “Exposure risks and ineffectiveness of total release foggers (TRFs) used for cockroach control in residential settings” has been published in the journal BMC Public Health.

An airplane spraying DDT over Baker County, Oregon as part of a spruce budworm control project, 1955. Credit: Wikimedia Commons.

DDT exposure in pregnant women linked to autism in offspring

An airplane spraying DDT over Baker County, Oregon as part of a spruce budworm control project, 1955. Credit: Wikimedia Commons.

An airplane spraying DDT over Baker County, Oregon as part of a spruce budworm control project, 1955. Credit: Wikimedia Commons.

A study that followed more than a million pregnancies in Finland found that elevated levels of a DDT (dichloro-diphenyl-trichloroethane) metabolite in the blood of pregnant women are associated with an increased risk for autism in newborns. DDT is an insecticide that was widely used around the world, including the United States, until it was banned.

DDT is one of the first modern synthetic insecticides — an organochlorine that was first synthesized in 1874. It soon proved to be highly effective for insect control in crop and livestock productions, but also around private homes and gardens. It also showed remarkable success in controlling malaria, typhus, and the other insect-borne human diseases. Through its use, the number of soldiers dying from malaria dropped from 400,000 in 1946 to less than 10 in 1950.

But insects quickly developed resistance, and people started spraying the environment with increased amounts of DDT to compensate.

Scientists would learn, however, that DDT provoked many long-lasting adverse effects on the environment and wildlife. In 1972, the EPA issued a cancellation order for DDT based on its adverse environmental effects, including potential human health risks.  Today, DDT is classified as a probable human carcinogen by U.S. and international authorities following animal studies that linked the insecticide to liver tumors. A 2014 study also found that British people with the highest levels of the chemical in their system were four times more likely to develop Alzheimer’s. 

One of the many environmental issues associated with DDT is that it persists for a very long time. Although it was banned more than three decades ago in Finland, people are still exposed to the chemical because it’s still in the soil where food is grown. Because chemicals can be transferred across the placenta, newborns also become contaminated with DDT.

In 2011, a study found that pregnant women exposed to the insecticide are much more likely to give birth prematurely, or to full-term but low birth weight babies. Now, researchers at Columbia University linked autism in offspring with DDT exposure in pregnant women.

The research team analyzed a dataset comprising a million pregnant Finnish women whose children were born between 1987 and 2005. Researchers identified 778 cases of childhood autism. Mothers with DDE levels — a metabolite of DDT —  in the top quartile were twice as likely to birth children with autism that have an intellectual disability than those in the bottom quartile. Overall, the rate of autism was one-third higher among offspring exposed to elevated levels of maternal DDE, the authors reported in the American Journal of Psychiatry.

“We think of these chemicals in the past tense, relegated to a long-gone era of dangerous 20th Century toxins,” says lead author Alan S. Brown, MD, MPH, professor of Epidemiology at Columbia University’s Mailman School of Public Health and of Psychiatry at Columbia University Medical Center.

“Unfortunately, they are still present in the environment and are in our blood and tissues. In pregnant women, they are passed along to the developing fetus. Along with genetic and other environmental factors, our findings suggest that prenatal exposure to the DDT toxin may be a trigger for autism.”

The researchers found no significant association between PCBs — another class of banned environmental pollutants — and autism.

One reason why maternal DDE exposure may increase the risk of autism in newborns is that the metabolite is associated with low birth weight, while PCB is not. Previously, a study on rats found that DDE inhibits androgen receptor binding, which might cause autism in the rat model. In contrast, PCBs increases androgen receptor transcription.

DDT is still manufactured and used to this day in some countries. However, it’s not employed for agricultural purposes. Some countries in Africa, Asia, and South America need the pesticide for mosquito control in order to reduce the risk of malaria.


Insecticides and low floral diversity are driving bumblebees into the ground

Bumblebee queens are finding it harder and harder to cope — and, as they go, so do their colonies.


Image credits Tim Hill.

It’s not easy being royalty, at least not if you’re a bumblebee. Every year after emerging from hibernation, bumblebee queens must prepare the nest, lay eggs, and rear larvae — all on their own. Needless to say, it’s a highly demanding job. And, if they fail to live up to it, there won’t be any colony. New research worryingly shows that we might be putting more on the plate of these single moms than they can shoulder.

Queen of an empty castle

The research team at the University of California Riverside reports that exposure to widely-used insecticide substances, along with poorer diets caused by reduced availability of flowers, are taking a toll on the queens. Since each must get the colony up and running by herself, the team is worried this effect will have drastic consequences on the bumblebees — a critical pollinator that’s already wavering.

Bumblebees play a key role in both natural and agricultural settings. They’re fuzzy and fast, meaning they can carry quite a lot of pollen around. They’re not picky, meaning they’ll pollinate virtually every flower they can get to. A lot of our crops today — from tomatoes to blueberries — heavily depend on bumblebees as the main pollinator species. However, unlike honey bees, bumblebee colonies need to be reset each year, starting from a single queen — making the species incredibly vulnerable during this phase.

“Queens are probably already a bottleneck for bumblebee population dynamics,” said Hollis Woodard, an assistant professor of entomology at the University of California Riverside and paper first author.

“If a queen dies because of exposure to humanmade stressors, then a nest full of hundreds of important pollinators simply won’t exist.”

Previous research has linked insecticide use — including neonicotinoids, one of the most widely-used of such compounds — with a decline in pollinator numbers. Neonicotinoids are usually applied to seeds, the team writes, but they can seep into the soil. And that’s where bumblebee queens hibernate. The compounds can also accumulate in the mature plant’s tissues, including its pollen and nectar.

Another factor that’s impacting bumblebees is declining floral diversity. This is mostly due to the use of land for agriculture and broader global changes that affect ecosystem integrity, such as climate change. According to the team, bumblebees “collect pollen from a wide variety of plant species,” and there is evidence that they need a mixed diet. Dining on pollen from a single species just doesn’t cut it for the fuzzy insects.

The team tested the effects of temporary and sustained exposure to imidacloprid — a neonicotinoid — on a queen’s mortality, activity, and ability to set-up a healthy nest. They also ran the test to see what effect a single source of pollen would have on those factors.

Their results showed that queens were significantly less active and six times more likely to die after sustained exposure to the pesticide (37 days). A shorter exposure (17 days) somewhat reduced these effects. More worryingly, even if the queens survived, they produced only a third of the eggs and a quarter of the larvae of untreated queens.

Monofloral pollen didn’t have such drastic effects, but it still noticeably influenced a queen’s activity levels and the size of its brood.

“Ours is the first study to explore the impact of multiple stressors on bumblebee queens during an understudied but important phase of their lives. It joins a small but growing body of research suggesting there are unique effects on queens that can have dramatic consequences for future generations,” Woodard said.

Woodard believes the findings are grounds for U.S. policymakers to reconsider the use of neonicotinoids. The EU has already set a ban on the use of these substances, to come into effect by the end of 2018.

Since bumblebees and pollinators on a whole are so immensely valuable to humanity, I hope Woodard’s warning is heeded.

The paper “Effects of neonicotinoid insecticide exposure and monofloral diet on nest-founding bumblebee queens” has been published in the journal Proceedings of the Royal Society B: Biological Sciences.

Insecticide is killing honeybees, causing colony collapse disorder

A Harvard study shows insecticides with neonicotionoids are devastating honeybee colonies, triggering colony collapse disorder.

Image via Wired.

Recently, we’ve written a lot about bees – because it’s a big deal. The National Agriculture Statistics Service reported that there were 2.44 million honey-producing hives in the United States as of February 2008, down from 4.5 million in 1980 – and it’s not much better in other parts of the world. Since three quarters of the world’s food require pollination, we’re talking about more than just bee populations. But it gets even worse: it’s also greatly affecting wild pollinators, and we still don’t know exactly why it’s happening (even though it’s pretty clear that we are the ones causing it, and there are some main suspects). Now, a new study from Harvard University claims to have figured out that problem, pointing to insecticides as the culprit.

“We demonstrated that neonicotinoids are highly likely to be responsible for triggering ‘colony collapse disorder’ in honeybee hives that were healthy prior to the arrival of winter,” said Chensheng Lu, an expert on environmental exposure biology at Harvard School of Public Health and who led the work.

Neonicotinoids are a class of neuro-active insecticides chemically similar to nicotine, and have been linked to damage caused to bees in insects for several years. Countries in the EU are already starting to ban the use of neonicotinoids, as the European Commission recommended a restriction of their use across the European Union but as usually, the US and Asia are lagging behind when it comes to environmental issues.

Connecting the dots

It was suspected for a long time that insecticides are directly connected with CCD, but due to the complexity of all the factors involved, it was pretty hard to directly connect the two. Now, researchers believe they’ve done that.

They monitored health of 18 bee colonies in three locations in central Massachusetts from October 2012 till April 2013. They treated two colonies with imidacloprid, two with clothianidin, and two were untreated control hives.

“Bees from six of the 12 neonicotinoid-treated colonies had abandoned their hives and were eventually dead with symptoms resembling CCD,” the team wrote. “However, we observed a complete opposite phenomenon in the control colonies.” Only one control colony was lost, the result of infection by the parasitic fungus Nosema and in this case the dead bees remained in the hive – this was not related to CCD.

This is a smoking gun for researchers, who were thrilled to report the findings.

“It is striking and perplexing to observe the empty neonicotinoid-treated colonies because honey bees normally do not abandon their hives during the winter,” the scientists wrote. “This observation may suggest the impairment of honey bee neurological functions, specifically memory, cognition, or behaviour, as the results from the chronic sub-lethal neonicotinoid exposure.”

So, the plan of action is simple (at least in the first stages) – stop using the damn neonicotinoid insecticides! They’re destroying bee populations. In European countries where this class of insecticides are banned, the cases of CCD have started to drop significantly, but in the UK, where the ban on neonicotinoids wasn’t implemented, CCD cases are peaking. The same goes for the US and China. After these substances are banned, we will probably see a stabilization of the bee (and wild pollinators) populations, and actually start thinking about how to regrow these populations. The solution is simple – we just have to do it.

Scientific Reference: Sub-lethal exposure to neonicotinoids impaired honey bees winterization before proceeding to colony collapse disorder.