The boll weevil (Anthonomus grandis) is a small beetle that originated in Central America and Mexico, first crossing into the United States near Brownsville, Texas, around 1892. It is an agricultural pest that exclusively targets cotton plants, feeding on the buds and flowers. Its arrival and subsequent spread throughout the U.S. cotton-growing regions established it as one of the most destructive agricultural pests in North American history, causing billions of dollars in crop losses.
Identifying the Boll Weevil
The adult boll weevil is a snout beetle (family Curculionidae). It measures less than 8 millimeters (about one-quarter inch) in length. The color of the adult insect can vary from a light yellowish-brown in younger weevils to a brownish-gray or almost black as they mature.
The most distinctive physical feature is its long, slender, and slightly curved snout, known as a rostrum, which is often about half the length of its body. This rostrum is used for puncturing the cotton plant’s fruiting structures for both feeding and egg-laying. It is also distinguished by two spurs located on the front femur of each leg.
The Cotton Connection: Life Cycle and Damage
The boll weevil’s existence is tied to the cotton plant, its sole host. The adult female uses her snout to chew a hole into an immature cotton square (the young flower bud) or a developing cotton boll. She then deposits a single egg inside this cavity, sealing the entry hole with a plug of frass (excrement).
The life cycle from egg to adult can be completed in two to three weeks, allowing up to ten generations per growing season. The most significant damage is inflicted by the larva, a legless, white grub that hatches inside the cotton structure and feeds internally on the tissue. This internal feeding causes the infested squares to drop off the plant prematurely (“flaring”), or it ruins the cotton fibers inside the boll, making them unsuitable for harvest.
Historical Significance and Economic Impact
The boll weevil’s rapid spread after its 1892 arrival in Texas was relentless, advancing an average of 70 miles each year until it infested all U.S. cotton-growing areas by the early 1920s. This infestation delivered a massive economic shock to the Southern United States, which had long relied on cotton monoculture. Crop losses in newly infested areas often ranged between 30 and 50 percent, costing cotton producers an estimated $22 billion in lost yields and control expenses since its arrival.
The devastation forced a shift in Southern agriculture, prompting farmers to diversify away from cotton production. For example, Georgia’s annual cotton production plummeted from 2.8 million bales in 1914 to just 600,000 bales ten years later. The widespread farm failures and economic hardship contributed to the Great Migration, as hundreds of thousands of African Americans and poor white farmers moved out of the rural South in search of better economic opportunities.
Modern Control and Eradication Efforts
Initial attempts to control the pest relied heavily on broad-spectrum chemical insecticides; at one time, one-third of all U.S. insecticides were applied to cotton to fight the weevil. This ineffective and environmentally damaging approach was replaced by the cooperative Boll Weevil Eradication Program (BWEP), which was officially launched in 1978. The BWEP utilizes an integrated pest management strategy that focuses on three main components.
Pheromone traps, which use a synthetic version of the male weevil’s aggregation scent, are deployed for monitoring and detection. When a weevil is detected, targeted applications of insecticides, such as malathion, are used to suppress the population. Cultural practices, including the rapid destruction of cotton stalks after harvest, eliminate the weevil’s food source and overwintering habitat before they enter a dormant state called diapause.
The program has been highly successful, eradicating the pest from more than 99 percent of U.S. cotton acreage and allowing farmers to significantly reduce their overall pesticide use. Today, eradication efforts are primarily focused on maintaining control along the border with Mexico, particularly in Texas, where re-infestation remains a constant threat.