The pesticide treadmill is a self-reinforcing cycle in which pests develop resistance to chemicals, forcing farmers to apply more pesticides or switch to stronger ones, which in turn breeds more resistance. The term was popularized by entomologist Robert van den Bosch in the 1970s, and the pattern he described has only accelerated since. As of 2024, 632 arthropod species have developed resistance to 364 different chemical compounds, accounting for nearly 19,000 documented resistance cases worldwide.
How the Cycle Works
The treadmill begins with a straightforward decision: a farmer sprays a pesticide to kill a damaging insect. The chemical works well at first, wiping out most of the population. But a small percentage of individuals in any pest population carry genetic traits that let them survive the exposure. Some can break down the toxic compound in their bodies. Others have subtle differences in the biological target the pesticide is designed to hit. A few simply change their behavior, avoiding treated surfaces or feeding at different times.
These survivors reproduce, and because the less-resistant individuals have been killed off, the next generation has a higher proportion of resistant pests. Species that breed multiple times per year accelerate this process dramatically, since each generation is another round of selection. Within a few seasons, the pesticide that once controlled the problem stops working.
At the same time, broad-spectrum pesticides don’t just kill the target pest. They also wipe out natural predators, parasites, and other beneficial insects that were keeping multiple pest species in check. With those biological controls gone, secondary pests that were never a problem before can suddenly explode in number. The farmer now has a new pest to deal with and reaches for another chemical, widening the cycle.
The Herbicide Version
The treadmill isn’t limited to insecticides. The same pattern plays out with weeds and herbicides. When genetically engineered crops resistant to glyphosate (the active ingredient in Roundup) became widespread, farmers could spray entire fields and kill every weed without harming the crop. It was remarkably effective, until weeds evolved glyphosate resistance. To combat these so-called “superweeds,” new crops were engineered to tolerate a different herbicide called dicamba. The dramatic increase in dicamba use has now led to dicamba-resistant weeds, plus widespread drift damage to neighboring farms growing susceptible crops. Meanwhile, total herbicide applied to soybeans has nearly doubled since 2006. Each new “silver bullet” becomes another step on the treadmill.
Rising Costs, Diminishing Returns
Global pesticide use in agriculture hit 3.7 million tonnes of active ingredients in 2022, double what it was in 1990. The amount applied per unit of cropland increased by 94 percent over that same period. In the United States, farm spending on pesticides rose from $33 million in the early 1930s to roughly $8.4 billion by the late 1990s. The cost per pound of active ingredient nearly doubled in just two decades, climbing from about $4.84 in the mid-1970s to $8.99 by the mid-1990s. Pesticides went from representing about 0.5 percent of total farm production costs after World War II to 4.6 percent by the late 1990s.
For individual farmers, the financial pressure is intense. Cotton farmers in India were spraying their crops 10 to 12 times per growing season to fight the American bollworm, which had developed resistance to cheap, widely used insecticides. Some sprayed as many as 14 times. The cost of all that chemical input, combined with diminishing effectiveness, pushed many into debt.
Collateral Damage to Ecosystems
A large-scale analysis integrating over 20,000 estimates from 1,705 experimental studies found that pesticides negatively affect a wide range of non-target organisms, not just the species they’re designed to kill. Insecticides, fungicides, and herbicides all reduced growth, reproduction, and survival in animals, plants, and soil microorganisms across both land and water systems. The researchers documented effects on more than 830 species, including invertebrates, amphibians, birds, and mammals.
Some of the consequences are counterintuitive. Insecticides designed to target crop-eating bugs also cause long-term declines in pollinators that visit mass-flowering crops. Fungicides reduce populations of beneficial soil fungi that help plants absorb nutrients. Herbicides can impair pollen viability in non-target plants. Each of these knock-on effects weakens the broader ecosystem that healthy agriculture depends on, creating yet another reason to spray more.
What Breaking the Cycle Looks Like
Integrated Pest Management, or IPM, is the most well-studied alternative. Rather than spraying on a fixed schedule, IPM monitors pest populations and only treats when damage is approaching an economically meaningful threshold. A three-year experiment across multiple farm sites found that IPM reduced insecticide applications by 95 percent compared to conventional management. Over 15 site-year growing seasons, IPM fields required just four total insecticide sprays, while conventionally managed fields received 77. Crop yields were maintained or improved, partly because wild pollinators recovered in the less-sprayed environment.
Regenerative agriculture takes the idea further by redesigning the farm itself. Instead of monocultures that are inherently vulnerable to pest outbreaks, regenerative systems use diverse plantings, cover crops, and practices that build soil biology. The results are striking: in comparative studies, insect pest populations were more than 10 times higher on insecticide-treated conventional farms than on insecticide-free regenerative farms. Regenerative fields did produce about 29 percent less grain per acre, but because input costs dropped so sharply, profits were 70 to 78 percent higher than on conventional operations.
The Indian cotton farmers who adopted IPM-style approaches saw similar results. One farmer who had been spraying 14 times per season cut back to once or twice and returned to profitability. Across the program, insecticide use dropped by 50 percent. These examples don’t eliminate pesticides entirely, but they break the core dynamic of the treadmill: the assumption that more chemistry is always the answer to a failing chemical approach.