How U.S. Cotton Growers Successfully Eradicated Pink Bollworm.

The pink bollworm, first recorded in the United States in the fall of 1917 near Hearne, Texas by entomologist Ivan Shiller, emerged as one of the most devastating cotton pests. Named for the distinctive pink hue of its larvae, the insect infiltrates cotton bolls, where its larvae consume seeds and fibers for approximately two weeks before crawling out to pupate. Once moths, they mate and perpetuate the cycle. With up to six generations each year and each female laying between 100 and 200 eggs per boll, pink bollworms are notoriously resilient—protected within bolls from many sprays—and winter larvae simply restart infestations in spring. Peter Ellsworth, an entomologist at the University of Arizona, summarized: “It’s such a difficult animal to control.”

By the mid-1960s, the pink bollworm had entrenched itself across New Mexico, Arizona, and California. By the year 2000, it was costing farmers approximately $32 million annually in both lost yield and pest control expenses.

Efforts beginning in the early 20th century—including insecticide applications, quarantines, delayed planting, and field sanitation—kept infestations at bay but never eliminated them. A particularly wet autumn in 1951 delayed harvest and right-in-field stalk destruction, which fueled a pink bollworm explosion in 1952 and spurred the formation of coordinated response teams, including USDA researchers, the National Cotton Council, and state agencies.

Among the breakthroughs was the sterile insect technique, first demonstrated in 1968. Entomologists Edward Knipling and Raymond Bushland pioneered the method: mass-rearing male bollworm moths, sterilizing them via precisely calibrated radiation that preserved mating ability, and releasing them to compete with wild males. Daily releases over 24 years in California’s San Joaquin Valley—a geographically contained cotton region with no active infestation—successfully prevented establishment of local pink bollworm populations. However, in infested desert regions, reliance on insecticide remained the norm, often proving ineffective and hazardous.

“Not only was pink bollworm spraying not very efficient, but it was hazardous,” recalled Ellsworth, who described the era as “existential” for U.S. cotton agriculture—unless a new solution emerged.

In the 1980s, an alternative emerged: genetically engineered Bt cotton. By inserting the cry1Ac gene from Bacillus thuringiensis, a bacterium producing insecticidal proteins, researchers created cotton plants that synthesized their own protection against lepidopterans—including pink bollworm. Tests showed remarkable results; aerial imagery revealed Bt cotton fields thriving amid decimated wild cotton.

In 1995, the EPA approved the first Bt cotton variety, and by 1996 it was planted on 12 percent of U.S. cotton acreage. Usage soared: by 1997, more than 60 percent of Arizona’s cotton crop was Bt. While environmental and health impacts from insecticides dropped significantly, pink bollworms remained a threat—notably capable of evolving resistance, which had already been documented in other pests.

To mitigate resistance, federal regulations required “structured refuges”—portions of fields planted with non-Bt cotton to maintain a population of insects susceptible to Bt. The strategy exploited recessive inheritance of resistance in pink bollworms: with refuges constituting 37 percent of acreage alongside 63 percent Bt cotton, resistant moths were overwhelmingly outnumbered and mated with susceptible counterparts, ensuring their offspring remained vulnerable to Bt toxins.

Though refuges delayed resistance, they also sustained low-level pink bollworm populations, making eradication impossible. In 2006, USDA-APHIS, growers, and the National Cotton Council launched an integrated pest management (IPM) eradication plan. This ambitious strategy phased out refuges entirely—replacing them with aggressive sterile-moth releases, mandatory 100 percent Bt cotton planting, pheromone-based mating disruption, cultural controls, and synchronised planting and harvest dates.

Bruce Tabashnik’s population models validated the plan: with enough sterile moths released, even resistant individuals would be overwhelmed. The EPA approved the strategy, and from 2006 to 2014, more than 11 billion sterile moths were released in Arizona alone. Farmers contributed 80 percent of program costs; in California, they collectively funded a moth facility in Phoenix, with USDA covering the remainder. Technologists optimized rearing, sterilization, and release methodology—down to low-altitude, slow-flying planes dropping live moths over fields.

The results were swift and dramatic. Before sterile releases began, Arizona faced more than 2 billion pink bollworms in 2005. One year later, sterile males outnumbered wild moths by vast margins, causing populations to crash. By 2010, none had been found in Arizona fields; by 2013, no wild moths were ever trapped. The USDA officially declared pink bollworm eradicated from U.S. cotton-growing regions in 2018, following a cautious five-year surveillance period with zero detected specimens.

Experts called the achievement “rare and hard to accomplish”—a testament to combined scientific innovation, dedicated grower participation, and unwavering regulatory support. As Ellsworth reflected, “We’ve created an extraordinary [integrated pest management] outcome that is safe to the environment and to the people… and preserved a crop and a culture and a rural economy that may have disappeared otherwise.”

Although eradication was certified, vigilance continues. Farmers and agencies maintain intensive monitoring systems to guard against resurgence. The pink bollworm saga stands as one of the most significant wins in modern agricultural pest management—an extraordinary demonstration of how integrated science, policy, and practice can overcome entrenched challenges.

Source:https://www.the-scientist.com/how-america-s-cotton-farmers-eradicated-the-pink-bollworm-73039

This is non-financial/medical advice and made using AI so could be wrong.