Johns Hopkins University researchers have presented unexpected new findings showing that the world’s most often used herbicide, glyphosate, can weaken the immune systems of bugs.
Glyphosate is a chemical compound. It’s the active ingredient in herbicides, like in the famous US brand of weed-killing products, “Roundup.” But the herbicide has been prevalently used in agriculture worldwide since the 1970s.
It kills unwanted plants by disrupting the shikimate pathway—a crucial metabolic process. Since the pathway is solely present in plants, people thought glyphosate was an ideal herbicide and harmless to everything but plants. However, recent concern over the chemical’s potentially hazardous effects on humans and the surrounding environment has led researchers to study glyphosate more closely.
The Hopkins team’s experiment involved mosquitos known to spread malaria and moths. Their findings suggest the chemical can increase the mosquito’s susceptibility to parasitic infection, perhaps increasing the risk of human disease transmission. This is very dangerous, especially for regions where malaria is endemic.
Arturo Casadevall, one of the study’s authors and a Bloomberg Distinguished Professor, said, “Our results show unexpected effects from a widely used herbicide and alert us to the fact that spreading these chemicals in the environment may have unintended consequences.”
The effects of glyphosate on bugs are still a source of much debate. Still, studies have found that the herbicide can disrupt insects’ gut bacteria, leading to physiological or behavioral changes. The new research suggests glyphosate could impair immunity in insects, which may lead to harmful consequences for human health.
The study authors said, “The finding that glyphosate appears to harm insects by interfering with their melanin production suggests the potential for a large-scale ecological impact, including impacts on human health.”
In 2001, Casadevall and colleagues studied the effect of glyphosate on fungi. They found that the chemical weakens the organism, inhibiting its production of melanin—a compound that facilitates pathogenic fungi’s resistance to the immune systems of animals they infect.
Melanin has its various functions within the animal kingdom. In humans, the molecule is commonly known as a light-absorbing pigment that shields the skin from ultraviolet radiation damage. In insects, it traps and kills invading bacteria, parasites, or fungal cells through a process called melanization—in which melanin molecules enclose the invading pathogen so other killer molecules can eradicate the invader.
The new study focused on examining the ill effects of disrupted melanin production in insects more closely. The team investigated the effects of glyphosate on two evolutionarily distant insect species: Galleria mellonella (the greater wax moth) and Anopheles gambiae (a type of African mosquito proven to carry malaria).
The scientists found glyphosate inhibited melanin production and made the bugs more prone to pathogenic disease in both models. But the mosquito investigations posed the most troubling findings. The mosquitoes became more vulnerable to infection by Plasmodium falciparum – a dangerous species of the malaria parasite. They found that glyphosate alters the composition of the fungal and bacterial population in the mosquito midgut (akin to the “gut microbiome” in humans), which helps regulate mosquito health.
Daniel Smith, one of the study’s co-authors and a Ph.D. candidate in Arturo Casadevall’s laboratory, said, “Mosquitoes exposed to glyphosate were less able to control Plasmodium infections they would have otherwise resisted, which hints that glyphosate exposure may make them better vectors for malaria. These results raise concerns about the increasing use of glyphosate in regions of the world where malaria is endemic.”
The results raise unease that glyphosate and possibly other phosphate-containing compounds are also harming insect populations. The idea that human items and tasks can accidentally disrupt everything in the surrounding ecosystem through the utilization of ordinary household or industrial chemicals that are widely accepted is frightful. Insects have many vital roles in the global ecosystem, and disrupting their populations could have significant adverse effects on people, agriculture, and the world of infectious diseases.
Therefore, the researchers are now studying the long-term, multi-generational after-effects of glyphosate on insect populations. More recently, a 2026 Virginia Tech study found that glyphosate also disrupts honeybee brain chemistry, cutting foraging activity by 13 percent and adding pollinators to the list of insects affected by the herbicide’s sublethal effects.
