09
May
Researchers Delve into Role of Gut Bacteria in Insect Resistance to Pesticides
(Beyond Pesticides, May 9, 2018) An insect’s gut microbiome plays an important role in conferring pesticide resistance, according to a new review published in the Annals of the Entomological Society of America. “Whether you’re looking at agricultural pests, household pests like cockroaches, or medical pests like disease-carrying mosquitoes, insects are great at adapting to whatever we throw at them, especially when it comes to different chemicals,†said lead author Jose Pietri, Ph.D to Entomology Today. The review adds to the numerous ways pests can evade the effects of chemical agriculture, reinforcing calls from recent studies showing that the best method of addressing this issue is to simply stop using synthetic pesticides and employ alternative pest management practices.
The authors identify two overarching methods through which microbes help confer resistance to toxic pesticides. The first involves the pest accepting a physiological trade-off, where a pest is able to better withstand an insecticide at the cost of losing its ability to regulate certain gut bacterium. For instance, diamondback moths resistant to fipronil and chlorpyrifos are found to contain higher levels of Lactobacillales, Pseudomonadales, and Xanthomonadales bacteria than non-resistant moths. While this trade-off affects the fitness of the organism, alterations of the bacterial community the pest is exposed to can reinforce and strengthen the pest. For example, culex mosquitoes that contain resistant genes can increase the likelihood that they will survive to adulthood through infection of a certain fungal parasite called Vavraia culicis.
The second method through which microbes could assist in conferring resistance to pests is directly through the bacterium. “There are several possible ways they can directly help insects deal with the toxins in insecticides, and one is a very direct mechanism whereby a toxin comes into the gut of an insect and, through enzymatic means, the microbes break it down and render it ineffective,†said Dr. Pietri. A specific example cited by authors was the development of fenitrothion (an organophosphate insecticide) resistance in bean bugs. During the nymph stage of the pest, the bugs pick up a soil bacterium called Burkholderia. Although generally uncommon, certain strains of Burkholderia have the ability to break down fenitrothion. However, when the chemical is continuously sprayed onto soil, fenitrothion-resistant Burkholderia become more common, leading to a greater number of bean bugs picking up the resistant strain of the bacterium.
This review underscores the variety of means insects can take advantage of in their environment to rapidly adapt to changing environmental factors. A 2013 study underscores this ability, finding that the common practice of “stacking†two or more Bacillus thuringiensis (Bt) toxins in genetically engineered plants did not work. Researchers assumed that pests resistant to the first Bt toxin would survive on the one-toxin plants, but die when consuming two-toxin plants because they had not yet developed resistance to the new formulation. However, pests selected for resistance to one toxin survived significantly better than caterpillars from a susceptible strain.
In the field, whether insect or weed, pests develop resistance because those that don’t die from toxic pesticide use develop some method to stop the chemical from causing it harm. A study published earlier this year in the journal Nature Ecology and Evolution found that the only tried and true method to reduce weed resistance was to eliminate the use of pesticides sprayed on target weeds.
While this study may lead to attempts to halt resistance to chemical pesticides, investigations of how microbes interact with insect detoxification could provide insight into new methods of bioremediation, or ways to model how humans may respond to changes in gut bacterial composition. There is already amble evidence that pesticide use alters the diversity of microflora in the human mouth and gut.
For more information about how chemical pesticides affect the human microbiome, see Beyond Pesticides’ Pesticides and You article on Monsanto’s Roundup, and the transcription of David Montgomery’s Talk at the 35th National Pesticide Forum titled Sustaining Life: From Soil Microbiota to the Gut Microbiome. Beyond Pesticides and the Organic Consumers Association have been given the green light from a Washington, DC Superior Court judge to sue Monsanto based on the argument that glyphosate (Roundup) has adverse impact on the gut biome and resulting adverse health effects. And to read more about pest and weed resistance, see visit our Genetic Engineering webpage.
 All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Annals of the Entomological Society of America, Entomology Today









(Beyond Pesticides, May 8, 2018) U.S. Environmental Protection Agency Administrator Scott Pruitt’s controversial
(Beyond Pesticides, May 7, 2018) Beyond Pesticides and The Organic Consumers Association (OCA) today responded to a federal judge’s ruling against Monsanto Co.’s motion to dismiss the groups’
(Beyond Pesticides, May 6, 2018) The Washington State Department of Ecology (Ecology)
(Beyond Pesticides, May 4, 2018)Â
(Beyond Pesticides, May 3, 2018) Hawaii’s bill to ban the dangerous, neurotoxic pesticide, chlorpyrifos, passed its final hurdle this week in the state legislature. Governor David Ige is expected to readily sign
(Beyond Pesticides, May 2, 2018) Granola, cereal, and wheat crackers all contain “a fair amount†of glyphosate, the herbicide in Monsanto’s popular Roundup, according to internal emails from the Food and Drug Administration (FDA). Although the results of these tests have not been formally released, FDA had stated it will be conducting tests for glyphosate in food. Previous reports have detailed the presence of glyphosate, the chemical classified as a “probable carcinogen,†in a wide range of foods and in people’s bodies.
(Beyond Pesticides, May 1, 2018) On April 27, 2018, European Union (EU) member states backed a proposal to further restrict uses of bee-toxic neonicotinoids finding the pesticides’ outdoor uses harm bees. These restrictions go beyond those already put in place in 2013, and now all outdoor uses of clothianidin, imidacloprid, and thiamethoxam will be banned. Uses will only be allowed in permanent greenhouses where contact with bees is not expected. This historic move in Europe comes as the U.S. Environmental Protection Agency (EPA) still drags its feet on finding neonicotinoids are too toxic for bees and other organisms and bans their use.
(Beyond Pesticides, April 27, 2018)Â Â After more than five years of intensive negotiations, European Members of Parliament (MEP) overwhelmingly passed the long-anticipated, new
(Beyond Pesticides, April 26, 2018)Â Each year, the
(Beyond Pesticides, April 25, 2018)Â A class-action lawsuit against two manufacturers of neonicotinoid insecticides is moving ahead in Quebec, Canada after an appeal to block the case by the Canadian government and the chemical companies, Bayer and Syngenta, was dismissed. In February 2018, the case, brought by a beekeeper, was allowed to proceed to trial by the Quebec Superior Court.
(Beyond Pesticides, April, 24, 2018) On April 19, 2018, an Appellate Court in California sided with the State of California, affirming that Monsanto’s glyphosate can be listed as a probable carcinogen under the state’s Proposition 65 and rejecting Monsanto’s challenge to law. The state will not only move ahead with warning labels on products that contain glyphosate but also prohibit discharge of the pesticide into public waterways.
(Beyond Pesticides, April 20, 2018) There is an extraordinary attack on local community rights to protect people and the environment from pesticides in the Republican Farm Bill, passed by the Agriculture Committee in the U.S. House of Representatives on April 18 on a straight party line vote. The language inserted in the Farm Bill amends the federal pesticide law with a provision that prohibits local governments from restricting pesticide use on private property within their jurisdictions. Local laws in two states, Maine and Maryland, will be overturned with final passage of this law in the U.S. House and Senate. In those 43 states that forbid local pesticide laws by state law, future reconsideration of this prohibition, pushed by the chemical and pest management industry, will be foreclosed. Local laws protecting the environment and public health have historically emerged out of local governments, with laws related to recycling, smoking, pet waste, building codes, and zoning.
(Beyond Pesticides, April 19, 2018)Â With the passage yesterday of the Republican amendments to the 2018 Farm Bill,Â
(Beyond Pesticides, April 18, 2018)Â
(Beyond Pesticides, April 17, 2018) In a case that appalled the nation, the U.S. Justice Department finally last week secured an indictment against an applicator who illegally applied a fumigant at a U.S. Virgin Island resort,
(Beyond Pesticides, April 16, 2018) Ethics scandals pile up regarding Environmental Protection Agency Administrator Scott Pruitt’s failure to do his job, leading to the
(Beyond Pesticides, April 13, 2018) Hawaii is poised to become the first state in the nation to prohibit the use of pesticides containing the developmental neurotoxicant, chlorpyrifos.
(Beyond Pesticides, April 12, 2018) The Justice Department will allow two notorious agrichemical corporations, Bayer and Monsanto, to merge, according to reports published earlier this week. Despite
(Beyond Pesticides, April 10, 2018) Current strategies aimed at managing herbicide resistant weeds in agriculture are not effective and may exacerbate weed problems, according to 
