Natural Solutions for Boll Weevils

Cultural Controls

• Weed control often helps to keep boll weevil populations low. The most valuable thing you can do for your cotton, however, is to delay planting your fields for as long as possible. The earliest planted fields often act as trap crops for boll weevils; the latest planted fields can be virtually weevil free until after their crops are finished. Weevils without cotton fields to consume will die, ultimately reducing populations.

Predatory Wasps

• Catolaccus grandis is a parasitic wasp that primarily preys upon the boll weevil. Admittedly, these wasps are a scatter-shot solution, being difficult to contain and control, but if your fields are plagued with boll weevils, C. grandis will find them. They are not yet widely available, but these insects have been experimentally released in Weslaco, Texas with promising results.

Beauvaria Bassiana

• Beauvaria bassiana is a fungus that targets a variety of insects, including beneficial ones, so use it with care. This fungus is available commercially in the form of spores mixed with liquid to simplify application. Thorough application is necessary, since this fungus must come in contact with the boll weevils to properly infest them.

Pheromone Traps

• Traps baited with male scent markers called aggregation pheromones have shown great promise when used correctly to protect cotton fields. These hormones are excreted by male boll weevils when they find cotton fields in the spring, acting like a scented sign-post to alert other weevils to the presence of food. The most effective traps are painted yellow and placed along the edges of cotton fields in early spring. Many of the adult boll weevils are tricked into the traps where they cannot escape.

Bt Cotton

• Bacillus thuringiensis is a host specific bacteria that has become invaluable to organic gardeners. It is generally used for control of caterpillars, but one strain, Bt San Diego, is effective against boll weevils. Plant scientists have taken this knowledge one step further and developed a cotton plant that contains genes from this strain of B. thuringiensis. Bt cotton is a genetically modified plant, but one that shows great promise in reducing both the use of pesticides in the battle against boll weevils and the boll weevils themselves. The very act of ingesting the cotton leads to the demise of the weevil.