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Insect Resistance Management Fact Sheet for Bacillus thuringiensis (Bt) Cotton Products

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Bt Cotton IRM Program

Specific Structured Refuge Requirements For Bollgard (Cry1Ac) (all regions), Bollgard II (Cry1Ac/Cry2Ab2) (Arizona, California, New Mexico, and west Texas only), and WideStrike (Cry1Ac/Cry1F) (Arizona, California, New Mexico, and west Texas only) Bt Cotton

All growers of Bt cotton must employ one of the following structured refuge options:

  1. 5% External, Unsprayed Refuge
    Growers must ensure that at least 5 acres of non-Bt cotton (refuge cotton) is planted for every 95 acres of Bt cotton. The size of the refuge must be at least 150 feet wide, but preferably 300 feet wide. This refuge may not be treated with sterile insects, pheromone, or any insecticide (except listed below) labeled for the control of tobacco budworm, cotton bollworm, or pink bollworm. At the pre-squaring cotton stage only, the refuge may be treated with any lepidopteran insecticide to control foliage feeding caterpillars. The refuge may be treated with acephate or methyl parathion at rates which will not control tobacco budworm or the cotton bollworm (equal to or less than 0.5 lbs active ingredient per acre). The variety of cotton planted in the refuge must be comparable to the Bt cotton variety, especially in the maturity date, and the refuge must be managed similarly to Bt cotton (e.g., planting time, use of fertilizer, weed control, irrigation, termination, and management of other pests). Growers must ensure that a non-Bt cotton refuge is maintained within at least ˝ linear mile (preferably adjacent to or within 1/4 mile or closer) from the Bt cotton fields.


  2. 20% External Sprayed Refuge
    Growers must ensure that at least 20 acres of non-Bt cotton are planted as a refuge for every 80 acres of Bt cotton (total of 100A). The variety of cotton planted in the refuge must be comparable to the Bt cotton variety, especially in the maturity date, and the refuge must be managed similarly to Bt cotton (e.g., planting time, use of fertilizer, weed control, irrigation, termination, and management of other pests). The non-Bt cotton variety may be treated with sterile insects, insecticides (excluding foliar Bacillus thuringiensis subsp. kurstaki (Btk) products), or pheromones labeled for control of the tobacco budworm, cotton bollworm, or pink bollworm. Growers must ensure that a non-Bt cotton refuge is maintained within at least 1 linear mile (preferably within ˝ mile or closer) from the Bt cotton fields.


  3. 5% Embedded Refuge
    Growers must plant at least 5 acres of non-Bt cotton (refuge cotton) for every 95 acres of Bt cotton. The refuge cotton must be embedded as a contiguous block within the Bt cotton field, but not at one edge of the field (i.e., refuge block(s) surrounded by Bt cotton). For very large fields, multiple blocks across the field may be used. For small or irregularly shaped fields, neighboring fields farmed by the same grower can be grouped into blocks to represent a larger field unit, provided the block exists within one mile squared of the Bt cotton fields and the block is at least 150 feet wide, but preferably 300 feet wide. Within the larger field unit, one of the smaller fields planted to non-Bt cotton may be utilized as the embedded refuge. The variety of cotton planted in the refuge must be comparable to the Bt cotton variety, especially in the maturity date, and the refuge must be managed similarly to Bt cotton (e.g., planting time, use of fertilizer, weed control, irrigation, and management of other pests). This refuge may be treated with sterile insects, any insecticide (excluding foliar Btk products), or pheromone labeled for the control of tobacco budworm, cotton bollworm, or pink bollworm whenever the entire field is treated. The refuge may not be treated independently of the surrounding Bt cotton field in which it is embedded (or fields within a field unit), except only at the pre-squaring cotton stage, when the refuge may be treated with any lepidopteran insecticide to control foliage feeding caterpillars.


  4. Embedded Refuge for Pink Bollworm Only
    Plant the refuge cotton as at least one single non-Bt cotton row for every six to ten rows of Bt cotton. The refuge may be treated with sterile insects, any insecticide (excluding foliar Btk products), or pheromone labeled for the control of pink bollworm whenever the entire field is treated. The in-field refuge rows may not be treated independently of the surrounding Bt cotton field in which it is embedded. The refuge must be managed (fertilizer, weed control, etc.) identically to the Bt cotton. There is no field unit option.

Natural Refuge for Bollgard II

Growers of Bollgard II and WideStrike Bt cotton in the southeastern U.S. may utilize a natural refuge instead of structrued refuge for insect resistance managment. Natural refuge consists of weeds, wild hosts, or other planted crops that can serve as alternate plant hosts for tobacco budworm and cotton bollworm. This type of refuge does not need to be managed by growers.

Natural refuge may be used only in the following states in the southeastern U.S.: Alabama, Arkansas, Florida, Georgia, Kansas, Kentucky, Louisiana, Maryland, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas (excluding the following counties: Brewster, Crane, Crockett, Culberson, El Paso, Hudspeth, Jeff Davis, Loving, Pecos, Presidio, Reeves, Terrell, Val Verde, Ward, and Winkler), and Virginia. Growers not in these areas must use one of the structured refuge options described in the previous section.

For specific information on the Bt cotton IRM programs, go the following websites

For further informathion contact:

Ombudsman, Biopesticides and Pollution Prevention Division (7511P)
Office of Pesticide Programs
Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, D.C. 20460

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