--June 3, 2002 Version--

A Remedial Action Plan for Responding to Pink Bollworm Resistance to Bt Cotton in Arizona

Formulated by the Arizona Bt Cotton Working Group T.J. Dennehy, Chair

I. Definitions

Definition #1. Putative Resistance Event--A Cautionary Alert

A putative resistance event consists of any field of Bt cotton in which collections of 100 bolls yield 3% or more large larvae (3rd instar or later), pupae or PBW exit holes in bolls and a test indicates that bolls from which large larvae were recovered were expressing Bt. This is a cautionary alert and must not be construed to be a verified resistance event until: 1) the plants from which collections were made are confirmed to produce Bt toxin and, 2) bioassays are completed that confirm the reduced susceptibility of the pink bollworm surviving on Bt cotton.

Definition #2. A Verified Resistance Event.

A putative resistance event becomes verified if three conditions are met:

II. Remedial Action

A. Putative Resistance Event: Year of First Detection.

Once a putative resistance event occurs, alternative PBW controls should be implemented in that field. Measures should include one or more of the following:

B. Verified Resistance Event: Year of First Detection
  1. If resistance is verified in time to permit it, we strongly recommend that measures be taken to reduce the numbers of resistant pink bollworm that survive to the next season. These could include: adulticide treatments, early termination, and early plowdown, consisting of shredding of stalks followed by discing, and deep plowing (6" burial). Winter irrigation is also recommended to reduce survivorship of overwintering larvae.
  2. Bt fields in the immediate vicinity of a verified resistance event should be examined to detect unusual survivorship of PBW. Results should be used to delimit the size of the affected area and to define the ‘Bt remedial action zone.’ We suggest sampling 300 bolls from Bt fields located within each of the 8 sections of land (designated by © in the adjacent figure) that surround the section of land on which the verified event (VE) occurred. Bt cotton fields in addition to the original VE field, containing 3% or more bolls infested with PBW should be considered affected by resistance for the purpose of delimiting the remedial action zone.
    figure of 3 rows of 3 squares; center square as copyright sign in it to represent resistance event
  3. The ‘Bt remedial action zone’ should be delineated using GPS mapping technology currently in use at the ACRPC. This will ensure accurate records of locations of verified resistance. The remedial action zone should include all sections of land falling within 6 miles of the perimeter of the section(s) of land in which verified resistance events occurred (see figure below).
  4. At such time as fields with verified resistance are detected in >3 different townships within a particular cotton growing region, the entire region may be designated as a Bt resistance remedial action zone.

C. Verified Resistance Event: Next Year’s Actions.
  1. Only non-Bt cotton or GM cotton that kills resistant individuals should be planted in the remedial action zone in the year(s) immediately following verification of resistance. This measure should be maintained until such time as bioassays of PBW from the remedial action zone demonstrate that the frequency of resistant individuals has declined to acceptable levels. What will constitute levels of resistance acceptable for allowing resumption of use of Bt cotton will be determined on an ad hoc basis by our Working Group, based on research experience that members have obtained from studies of pink bollworm resistance to Cry1Ac.
  2. It is assumed that published University recommendations for monitoring and chemical control of pink bollworm will be followed within remedial action zones in order to limit survival of resistant pink bollworm. Additionally, timely crop termination (no production of bolls after Sept. 15) and early and thorough crop destruction, as detailed above, is strongly encouraged. The feasibility of releases of sterile pink bollworm should be investigated.
  3. The recommendations of our working group regarding 1) Bt refuge management and 2) remedial action for responding to PBW resistance in Arizona should be re-evaluated annually and modified to account for new findings. Educational programs and regulatory measures should be devised to promote a high level of producer compliance with recommendations.

III. Recommended Organizational Roles

  1. The Arizona Department of Agriculture within its organizational framework should serve a central role in implementing this plan, compiling statistics on use of Bt cotton, and promoting compliance with remedial action.
  2. A sampling team comprising personnel from relevant organizations (ACRPC, UA, USDA) will be formed. This team will be ready in August of every year to conduct the sampling required to delineate resistance problems (as detailed above). Similarly, facilities and personnel at EARML will be prepared to conduct bioassays of up to 20 different populations of PBW per season. Funding for these efforts must be sustained.
  3. Registrants should agree to suspend Bt cotton sales in remedial action zones until such time as either the frequency of resistant individuals is shown to have declined to levels deemed acceptable by our Working Group, or new Bt products free of cross-resistance are introduced, and the Arizona Bt Cotton Working Group has concluded that a modified resistance management strategy has been adopted that will adequately reduce the rate of development of further resistance to Bt cotton products.


picture of concentric circles around center of 8 squares with 3 containing resistance events. Concentric circles extend to diameter of 6 miles beyond the edge of the infected field

IV. Select Resistance References from the AZ Bt Cotton Working Group

Bartlett, A.C., T.J. Dennehy and Larry Antilla. 1997. An evaluation of resistance to B.t. toxins in native populations of the pink bollworm. Proc. 1997 Beltwide Cotton Conferences. pp. 918-921.

Simmons, A. L., T. J. Dennehy, B. E. Tabashnik, L. Antilla, A. Bartlett, D. Gouge, and R. Staten. 1998. Evaluation of B.t. cotton deployment strategies and efficacy against pink bollworm in Arizona. Proc. 1998 Beltwide Cotton Conf. 2: 1025-1030.

Liu, Y. B., B. E. Tabashnik, T. J. Dennehy, A. L. Patin, A. C. Bartlett. 1999. Development time and resistance to Bt crops. Nature 400: 519.

Patin, A. L., T. J. Dennehy, M. A. Sims, B. E. Tabashnik, Y. B. Liu, L. Antilla, D. Gouge, T. J. Henneberry and R. Staten. 1999. Status of pink bollworm susceptibility to B.t. in Arizona. Proc. 1999 Beltwide Cotton Conf. 2: 991-996.

Tabashnik, B. E., A. L. Patin, T. J. Dennehy, Y. B. Liu, E. Miller and R. Staten. 1999. Dispersal of pink bollworm (Lepidoptera: Gelechiidae) males in transgenic cotton that produces a Bacillus thuringiensis toxin. J. Econ. Entomol. 92: 772-780.

Walters, M., R. Staten, R. Sequeira, and T.J. Dennehy. 1999. Preliminary analysis of pink bollworm population distributions in a large acreage of genetically engineered cotton with regard to resistance management. Proc. 1999 Beltwide Cotton Conferences. pp.989-991.

Tabashnik, B. E., Y. B. Liu, R. A. deMaagd and T. J. Dennehy. 2000. Cross-resistance of pink bollworm (Pectinophora gossypiella) to Bacillus thuringiensis toxins. Appl. Environ. Microbiol. 66: 4582-4584.

Tabashnik, B. E., A. L. Patin, T. J. Dennehy, Y. B. Liu, Y. Carrière, M. A. Sims, and L. Antilla. 2000. Frequency of resistance to Bacillus thuringiensis in field populations of pink bollworm. Proc. Nat'l. Acad. Sci. USA 97: 12,980-12,984.

Tabashnik, B. E., R. T. Roush, E. D. Earle, A. M. Shelton. 2000. Resistance to Bt toxins. Science 287: 42.

Antilla, L., M. Whitlow, B. Tabashnik, T. Dennehy and Y. Carrière. 2001. Benefits of multi-level monitoring activities for a pink bollworm resistance management program in transgenic (Bt) cotton in Arizona. 2001 Proc. Beltwide Cotton Conf. 2: 1173-1175.

Carrière, Y., C. Ellers-Kirk, B. Pederson, S. Haller, and L. Antilla. 2001. Predicting spring moth emergence in the pink bollworm: implications for managing resistance to transgenic cotton. J. Econ. Entomol. 94: 1012-1021.

Carrière, Y., T. J. Dennehy, B. Pedersen, S. Haller, C. Ellers-Kirk, L. Antilla, S. Haller, Y. B. Liu, E. Willott and B. E. Tabashnik. 2001. Large-scale management of insect resistance to transgenic cotton in Arizona: can transgenic insecticidal crops be sustained? J. Econ. Entomol. 94: 315-325.

Carrière, Y., C. Ellers-Kirk, Y. B. Liu, M. A. Sims, A. L. Patin, S. Meyer, T. J. Dennehy and B. E. Tabashnik. 2001. Fitness costs and maternal effects associated with resistance to transgenic cotton in the pink bollworm (Lepidoptera: Gelechiidae). J. Econ. Entomol. 94: 1571-1576.

Carrière, Y., C. Ellers-Kirk, A. L. Patin, M. Sims, S. Meyer, Y. B. Liu, T. J. Dennehy and B. E. Tabashnik. 2001. Overwintering cost associated with resistance to transgenic cotton in the pink bollworm. J. Econ. Entomol. 94: 935-941.

Carrière, Y., and B. E. Tabashnik. 2001. Reversing insect adaptation to transgenic insecticidal plants. Proc. Roy. Soc. London B 268: 1475-1480.

Herrero, S., J. González-Cabrera, B. E. Tabashnik and J. Ferré. 2001. Shared binding sites in Lepidoptera for Bacillus thuringiensis Cry1Ja and Cry1A toxins. Appl. Environ. Microbiol. 67: 5729-5734.

Liu, Y. B., B. E. Tabashnik, S. K. Meyer, Y. Carrière and A. C. Bartlett. 2001. Genetics of pink bollworm resistance to Bacillus thuringiensis toxin Cry1Ac. J. Econ. Entomol. 94: 248-252.

Liu, Y. B., B. E. Tabashnik, S. K. Meyer, and N. Crickmore. 2001. Cross-resistance and stability of resistance to Bacillus thuringiensis toxin Cry1C in diamondback moth. Appl. Environ. Microbiol. 67: 3216-3219.

Liu, Y. B., B. E. Tabashnik, T. J. Dennehy, Y. Carrière , M. A. Sims and S. K. Meyer, and Y. Carrière. 2001. Effects of Bt cotton and Cry1Ac toxin on survival and development of pink bollworm (Lepidoptera: Gelechiidae). J. Econ. Entomol. 94: 1237-1242.

Meyer, S. K., B. E. Tabashnik, Y. B. Liu, M. C. Wirth and B. A. Federici. 2001. Cyt1A from Bacillus thuringiensis lacks toxicity to susceptible and resistant larvae of diamondback moth and pink bollworm. Appl. Environ. Microbiol. 67: 462-463.

Moulton, J.K. and T.J. Dennehy. 2001. Beet armyworm resistance to Cry1Ac. Proceedings Beltwide Cotton Conferences. National Cotton Council. pp. 989-991.

Sims, M. A., T. J. Dennehy, A. Patin, Y. Carrière, Y. B. Liu, B. E. Tabashnik, L. Antilla, and M. Whitlow. 2001. Arizona’s multi-agency resistance management program for Bt cotton: sustaining the susceptibility of pink bollworm. 2001 Proc. Beltwide Cotton Conf. 2: 1175-1179.

Tabashnik, B. E. 2001. Breaking the code of resistance. Nature Biotechnology 19: 922-924.

Tabashnik, B. E., T. J. Dennehy and Y. Carrière. 2001. Supporting a cautious approach to agricultural biotechnology. BioScience 51: 905-906.

Liu, Y. B., B. E. Tabashnik, T. J. Dennehy, Y. Carrière, M. A. Sims and S. K. Meyer. 2002. Oviposition on and mining in bolls of Bt and non-Bt cotton by resistant and susceptible pink bollworm (Lepidoptera: Gelechiidae). J. Econ. Entomol. 95: 143-148.

Sims, M. A., T. J. Dennehy, L. Shriver, D. Holley,Y. Carrière and B. E. Tabashnik. 2002. Susceptibility of Arizona pink bollworm to Cry1Ac. 2002. Proc. Beltwide Cotton Conf. National Cotton Council, Memphis, TN.

Tabashnik, B. E. T. J. Dennehy, Y. Carrière, Y. B. Liu, S. K. Meyer, A. Patin and M. A. Sims. 2002. Resistance management: slowing pest adaptation to transgenic crops. Acta Scandinavica, Section B, Soil and Plant Science: in press.

Tabashnik, B. E., Y. B. Liu, T. J. Dennehy, M. A. Sims, M. S. Sisterson, R. W. Biggs and Y. Carrière. 2002. Inheritance of resistance to Bt toxin Cry1Ac in a field-derived strain of pink bollworm (Lepidoptera: Gelechiidae). J. Econ. Entomol.: in press.

Tabashnik, B. E. 2002. Review of "Lords of the Harvest: Biotech, Big Money, and the Future of Food" by Daniel Charles. Quarterly Review of Biology. In press.

Tabashnik, B. E. 2002. Pesticide resistance. Pp. 880-883, In: M. Pagel (ed.), Encyclopedia of Evolution.


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Last update: September 13, 2003.