Plant Biotechnology: Current and Potential Impact For Improving Pest Management In U.S. Agriculture An Analysis of 40 Case Studies June 2002 Insect Resistant Cotton (2) Leonard P. Gianessi Cressida S. Silvers Sujatha Sankula Janet E. Carpenter National Center for Food and Agricultural Policy 1616 P Street, NW Washington, DC 20036 Phone: (202) 328-5048 Fax: (202) 328-5133 E-mail: ncfap@ncfap.org Website: www.ncfap.org Financial support for this study was provided by the Rockefeller Foundation, Monsanto, The Biotechnology Industry Organization, The Council for Biotechnology Information, Grocery Manufacturers of America, and CropLife America.
33. Cotton Insect Resistant (2) Production In the US, just over seventeen million bales of cotton (8.2 billion pounds) were harvested from 13 million cotton acres in 2000. This acreage is consistent with 1999 cotton acreage and production and represents an increase from the 14 million bales produced on 10.6 million acres in 1998 [23]. Total cotton crop value in 2000 was $4.8 billion. The vast majority of the cotton is upland varieties with a minority of higher value, extra long staple cotton produced in CA, AZ, NM and TX. Currently, seventeen states contribute to US production (see Table 33.1). Lepidopteran Insect Pests The fall armyworm, soybean looper and the beet armyworm are destructive migratory pests of many crops in the southeastern US. Loopers and armyworms overwinter south of the freeze line-in Florida and coastal areas. Large populations also migrate from Central and South America and the Caribbean islands. In California, the beet armyworm overwinters in the soil as a pupa. Primary damage caused by fall armyworms on cotton is from their feeding on the fruit. The larger, more mature larvae may completely devour squares. They feed extensively on blooms and severely damage bolls by eating the interior portions [27]. When compared to the defoliation pattern of other foliage feeding caterpillars, the defoliation pattern of soybean loopers is unusual: soybean loopers feed from the inside out on plant canopy. In a heavy soybean looper population, the outer canopy will appear undamaged until all the lower leaves on the plant are almost destroyed. Once loopers begin feeding on the outer canopy, they can completely defoliate the plant in 36 to 48 hours [28]. Young beet armyworm larvae feed together and gradually disperse as they grow. They skelotenize leaves. Older larvae chew irregular pieces from leaves and may also feed on squares, flowers, and small bolls [29]. 2
Large populations of beet armyworms occur in years with dry summers. During these years many of the parasites (wasps and diseases) that help keep beet armyworm populations in check are reduced [30]. Populations of armyworms often increase following the application of insecticides for other pests, which in turn reduce the natural enemy populations [31]. In recent years beet armyworms have become a greater problem in California cotton due to increased planting nearby of other susceptible hosts such as tomatoes [32]. Table 33.2 tracks estimates of infestation levels of beet armyworm/fall armyworm/soybean looper in cotton by state 1990-2001. Years with higher than normal infestations in Texas, Oklahoma, and New Mexico are generally the result of drought conditions. In the drought year of 2000 beet armyworms were at their highest level in Texas since 1980 [26]. Some growers sprayed four times to control BAW. In other states such as North Carolina, infestation levels of BAW are dependent on how far north the pest migrates during the season [26]. These migratory pests advance farther in years with higher than normal early season temperatures. There is some concern that Boll Weevil Eradication Program sprays may contribute to outbreaks of beet armyworms, but there is no definitive data to support that possibility [26]. Bt Cotton I Transgenic Bt cotton, expressing the Cry1Ac insecticidal d-endotoxin of Bacillus thuringiensis Berliner, has been commercially available in the United States since 1996. Table 33.3 delineates Bt cotton adoption by state in 2000. Since then, B. thuringiensis (Bt) cotton has demonstrated remarkable control of some lepidopteran pests, particularly the tobacco budworm and the pink bollworm. Since its release into commercial markets, Bt cotton seldom, if ever, has required supplemental insecticide control for these two pests [3]. Control of the bollworm has been less dependable, and economically damaging 3
infestations of this pest can occur on Bt cotton, particularly after plants have begun flowering and when insecticides have disrupted populations of predators and parasites. The bollworm is inherently more tolerant than tobacco budworm to the Cry1Ac d- endotoxin expressed in currently available Bt cultivars. Additionally, low expression of the toxin in some plant parts, such as in pollen and petals, has been implicated in increased survival of the bollworms on Bt cotton [3]. Other common lepidopteran pests such as fall armyworms, beet armyworms and soybean loopers are even more tolerant than bollworms to Cry1Ac. Bollgard cottons in North Carolina frequently require supplemental bollworm control with insecticides. The major bollworm flight to cotton occurs in North Carolina in late July to early August. The invasion period coincides with the observed drop in average levels of Cry1Ac in cotton fruit [17]. Supplemental foliar insecticide applications (e.g., pyrethroids) have been used in many Bt cotton fields to control economically damaging populations of fall armyworms, beet armyworms, soybean loopers and especially bollworms [2]. Table 33.4 lists the insecticides recommended for budworm/bollworm control. The average use rate for these insecticides is.25 lb AI/A. Table 33.5 displays estimates of current Bt cotton acreage treated with insecticides specifically for supplemental bollworm control. Approximately 36% of current Bt cotton acreage is treated (1.9 million acres) with 527700 pounds of chemical active ingredients. Cotton yield losses to bollworms are occurring on current Bt acreage even with the supplemental sprays. In addition, some Bt cotton acreage is not receiving a supplemental spray, and losses are occurring. Table 33.6 delineates cotton losses to bollworms on Bt cotton acreage by state. Approximately 65000 bales valued at $19 million were lost to bollworms on Bt cotton acreage in 2000. Table 33.7 lists the insecticides recommended for fall armyworm/beet armyworm/soybean looper control. The average use rate for these insecticides is.423 lb AI/A. Table 33.8 displays estimates of current Bt cotton acreage treated with insecticides specifically for beet armyworm/fall armyworm/soybean looper control. Approximately 21% of current Bt cotton acreage is treated with 458955 pounds of chemical active 4
ingredients. Cotton yield losses to loopers and armyworms are occurring on current Bt acreage even with the supplemental sprays. In addition, some Bt cotton acreage is not receiving a supplemental spray, and losses are occurring. Table 33.9 delineates cotton losses to loopers and armyworms on Bt cotton acreage by state. Approximately 12000 bales valued at $3.6 million were lost to loopers/armyworms on Bt cotton acreage in 2000. Table 33.10 summarizes the losses in production volume and value and the costs and amounts of sprays due to bollworms/armyworms/loopers on Bt cotton acreage in 2000. Bt Cotton II Unacceptable control of bollworms and other lepidopteran pests such as beet armyworms, fall armyworms and soybean loopers, prompted the development of a new genetically modified cotton that contains two separate crystalline proteins [4]. Bollgard II cotton was developed by incorporating the Cry2Ab protein from Bacillus thuringiensis into a commercially available Bollgard cotton cultivar, Deltapine 50B, which contains the Cry1Ac protein. Bollgard II was produced by particle bombardment, transforming DP50B and adding the Cry2Ab gene [16]. Cloned plants regenerated from the transformed tissue expressed both the Cry1Ac protein and the Cry2Ab protein. These genes also segregated independently [19]. The Cry2Ab protein was added to provide greater insecticidal activity against target pests and broaden the spectrum of total pests controlled. A three-to-six-fold increase was observed in bioactivity of Bollgard II compared with Bollgard against tobacco budworm [4]. Plant expression of Cry2Ab is approximately 10-times higher than for Cry1Ac resulting in an efficacy contribution that is equal to or greater than Cry1Ac on the important lepidopteran insects in US cotton production [14]. The addition of Cry2Ab protein expressed in Bollgard II cotton provides satisfactory control of beet armyworms, fall armyworms, and soybean loopers [2]. Also, efficacy of Bollgard II was improved over Bollgard against bollworms. Field studies indicate that 5
Bollgard II cottons will consistently provide satisfactory bollworm control [4]. Researchers observed improved bollworm control in Bollgard II cotton compared with Bollgard cotton during 1999. These initial data indicate that Bollgard II will be beneficial in areas where multiple lepidopteran pest species reach economically damaging levels during most years [4]. The dual-toxin cultivars, expressing Cry1Ac and Cry2Ab, may not require supplemental insecticide applications for these pests [3]. Supplemental applications of insecticide may only be necessary for other pests (aphids, sucking bugs, etc.) that are not impacted by proteins in Bollgard II genotypes [7]. In Texas and Arizona, beet armyworm per acre averaged across three sites were 389 for Bollgard II, 11,621 for Bollgard and 24,682 for conventional cotton. Soybean looper larvae numbers and foliage damage was significantly lower for Bollgard II compared to conventional and Bollgard varieties [5]. Very few fall armyworms were found in Bollgard II plots compared to Bollgard or conventional cotton [6]. For fall armyworm, plots containing dual-toxin cotton reduced larvae by 96% over both non-bt and single-toxin cotton in 1999 and 2000. Populations of soybean looper were also significantly reduced in plots containing dual-toxin cotton [8]. Reports from field and greenhouse trials conducted in North Carolina demonstrated that Bollgard II genotypes significantly reduced numbers of susceptible and Cry1Ac-tolerant bollworm larvae below that of the Bollgard cottons. These greenhouse data and those from field studies suggest that the commercialization of the dual-gene construct would reduce bollworm damage over that experienced by Bollgard varieties, as well as eliminate the need for supplemental insecticide applications for bollworm control [9]. The data collected in research studies shows that the dual Bt varieties were protected from beet armyworm, tobacco budworm, soybean looper and cabbage looper (see Table 33.11) [12] [11] [6]. 6
Bollgard II cotton was evaluated in over 40 small plot field trials across the southeastern states of Alabama, Florida, Georgia, South Carolina, North Carolina and Virginia during the field season of 2000. Bollgard II consistently decreased the amount of square and boll damage compared to Bollgard or conventional cotton [13]. In one test, bollworm, beet armyworm and cabbage looper appeared in the field very late in the season. All counts in the Bollgard II were zero and statistically different from Bollgard and DPL 50 [15]. The dual-toxin Bt cultivars will give better control of bollworms than those expressing only Cry1Ac. The control of a large and naturally occurring population of soybean looper by the dual-toxin cultivars was very good (>90%), and it seems unlikely that dualtoxin cultivars (expressing Cry2Ab) would require treatment for this pest [18]. Several field tests on Bollgard II varieties were conducted during the 1999 season in South Carolina. No supplemental treatments were required for Bollgard II cotton genotypes. In conventional cotton, applications were required for bollworm control. Bollgard II cottons show considerable promise of controlling major lepidopterous pests with little need for applications to supplement their control [20]. Data suggest that dual-toxin Bt (Bollgard II) cottons will provide substantially better control of lepidopteran pests compared with the existing, single-toxin Bt cultivars. The superiority of these dual-toxin cultivars will probably be most apparent for soybean looper, beet armyworm and fall armyworm because these species are affected less than bollworm by the existing, single-toxin cultivars [18]. However, control of bollworm populations should also be improved. Estimated Impacts Bollgard cotton will likely be phased out and completely replaced with Bollgard II; a process that will take several years [14]. 7
It is estimated that Bt cotton II will be adopted on the same acreage that is currently planted with Bt cotton I at an increased cost of $2/A. The major impact of Bt cotton II would be an elimination of current losses and spraying costs due to bollworms/loopers/armyworms on Bt cotton acreage. These impact estimates are shown in Table 33.12. It is estimated that Bt cotton would increase cotton production by 37 million pounds with a value of $22 million and reduce pesticide use by 986000 pounds. Adoption rates for Bt cotton II may actually be higher than Bt cotton I in California and Texas due to the more widespread infestation of beet armyworms in those states. 8
Table 33.1 Cotton Production By State: 2000 Harvested Yield (lbs/a) Production Value (million $) Acres (000) (000 bales/yr.) Alabama 530 489 540 141 Arizona 284 1302 770 222 Arkansas 950 733 1450 395 California 914 1339 2550 897 Florida 106 453 100 27 Georgia 1350 583 1640 453 Kansas 37 298 23 6 Louisiana 695 628 910 236 Mississippi 1280 649 1730 416 Missouri 388 668 540 152 New Mexico 90 736 137 37 North Carolina 925 747 1440 422 Oklahoma 170 438 155 42 South Carolina 290 629 380 115 Tennessee 565 607 715 187 Texas 4416 433 3980 987 Virginia 108 707 159 47 Total 13098 631 17219 4782 480 pound bales Source [23] [24] Table 33.2 Acres Infested with Fall Armyworm/Beet Armyworm/Soybean Looper 90 91 92 93 94 95 96 97 98 99 00 01 AL 95 100 100 100 100 100 84 98 100 29 5 1 AZ 22 24 98 80 80 75 92 100 76 54 61 15 AR 5 0 1 64 39 35 27 11 42 0 75 20 CA 35 10 14 6 0 10 8 38 25 39 31 80 FL 100 100 5 100 27 100 25 65 100 10 40 7 GA 92 56 55 100 28 48 63 100 100 3 6 2 LA 30 16 9 100 90 100 66 65 100 61 100 69 MS 27 100 100 100 86 100 57 71 100 64 100 32 MO 0 4 0 52 14 55 0 3 66 10 12 0 NM 11 27 12 13 28 51 2 1 80 0 53 0 NC 91 2 53 46 25 100 0 34 80 25 12 3 OK 17 0 <1 13 13 40 19 0 75 5 25 2 SC 78 72 100 100 23 79 26 36 62 5 2 <1 TN 5 2 <1 33 6 11 <1 1 60 5 94 34 TX 6 10 10 5 14 82 31 18 78 33 79 51 VA 0 0 0 0 0 0 0 0 <1 0 0 0 Source: [21] 9
Table 33.3 Adoption of Bt Cotton by State (2000) Harvested Acres (000) % Bt 1 Bt Acres (000) AL 530 65 344 AZ 284 57 162 AR 950 60 570 CA 914 6 46 FL 106 75 80 GA 1350 48 648 LA 695 81 563 MS 1280 75 1024 MO 388 5 85 NM 90 36 25 NC 925 41 379 OK 170 55 94 SC 290 71 209 TN 565 76 429 TX 4416 10 442 VA 108 41 44 Total 13061 39 5144 1 Source: [25] Table 33.4 Insecticides Recommended for Budworm/Bollworm Control (lb/ai A) Acephate 1.00 Bifenthrin 0.06 Cyfluthrin 0.04 Cypermethrin 0.05 Deltamethrin 0.02 Esfenvalerate 0.04 Indoxacarb 0.11 Lambdacyhalothrin 0.03 Methomyl 0.45 Profenofos 1.00 Spinosad 0.08 Thiodicarb 0.60 Tralomethrin 0.02 Zetamethrin 0.04 Average 0.25 Source: [22] 10
Table 33.5 Bt Cotton Acreage Sprayed for Bollworms (2000) Bt Acres (000) % Sprayed 1 Bt Acres Sprayed (000) # of Sprays/A $/Spray $/yr. (000) Lbs AI/yr 2 AL 344 1.5 5 1.0 9.07 45 1250 AZ 162 1.1 2 1.0 16.37 33 500 AR 570 71.4 407 1.0 13.00 5291 101750 CA 46 1.1 1 1.0 16.37 16 250 FL 80 2.4 2 1.0 9.00 18 500 GA 648 25.0 162 1.0 10.00 1620 40500 LA 563 45.7 257 1.5 7.04 2714 96375 MS 1024 34.1 349 1.1 13.20 5067 95975 MO 85 1.3 1 1.0 8.34 8 250 NM 25 16.7 4 1.0 18.00 72 1000 NC 379 70.0 265 1.0 8.25 2186 66250 OK 94 3.6 3 1.0 12.75 38 750 SC 209 82.2 172 1.5 8.75 2257 64500 TN 429 29.6 127 1.0 11.32 1437 31750 TX 442 12.2 54 1.0 10.74 580 13500 VA 44 95.0 42 1.2 11.00 554 12600 Total 5144 36.0 1853 21936 527700 1 [21] Data for 2000 (NC for 2001). California Assigned AZ data 2 Calculated at.25lb AI/A multiplied by the number of sprays per acre. 11
Table 33.6 Cotton Losses to Bollworms on Bt Cotton Acreage (2000) Bt Acres (000) Bales Lost 1 per Bt A Total Bales Lost Total Loss 2 ($ 000) AL 344.0111 3818 1099 AZ 162.0053 859 247 AR 570.0111 6327 1822 CA 46.0053 244 70 FL 80.0111 888 256 GA 648.0111 7193 2072 LA 563.0111 6249 1799 MS 1024.0111 11366 3273 MO 85.0162 1377 396 NM 25.0053 132 38 NC 379.0271 10271 2958 OK 94.0053 498 143 SC 209.0271 5664 1631 TN 429.0162 6950 2001 TX 442.0053 2343 675 VA 44.0271 1192 343 Total 5144 65371 18823 1 Derived from [21] for AZ, LA, NC and TN. Assigned to neighboring states. 2 Calculated at $288/Bale. 12
Table 33.7 Insecticides Recommended for Soybean Looper, Beet Armyworm, Fall Armyworm (Lb. AI/A) Acephate 1.00 Chlorpyrifos 0.62 Diflubenzuron 0.09 Indoxacarb 0.10 Methomyl 0.40 Profenofos 0.90 Spinosad 0.08 Thiodicarb 0.75 Methoxyfenozide 0.11 Tebufenozide 0.18 Avg. 0.423 Source: [22] 13
Table 33.8 Bt Cotton Acreage Sprayed for Fall Armyworm/ Beet Armyworm/Soybean Looper (2000) Bt Acres (000) % Sprayed 1 Bt Acres Sprayed (000) $/Spray Spray Cost $/yr. (000) Lbs AI/yr 2 AL 344 2 7 14.92 103 2961 AZ 162 5 8 6.50 53 3384 AR 570 26 148 13.00 1927 62604 CA 46 5 2 6.50 13 846 FL 80 0 - - - - GA 648 4 26 12.00 311 10998 LA 563 80 450 9.03 4067 190350 MS 1024 23 235 11.73 2763 99405 MO 85 4 3 11.00 33 1269 NM 25 6 2 21.00 32 846 NC 379 0 - - - - OK 94 5 5 16.50 78 2115 SC 209 0-16.00 - - TN 429 0 - - - - TX 442 45 199 14.48 2880 84177 VA 44 0 - - - - Total 5144 21 1085 11.29 12260 458955 1 Derived from [21]. Estimates for AZ, LA, NC and TN are specific for Bt acreage. Estimates for other states are derived from statewide data. Data for 2000 except TN (1999) and NC (2001). California estimates assigned from AZ. 2 Calculated at.423lb AI/A 14
Table 33.9 Cotton Losses to BAW/FAW/SL on Bt Cotton Acreage (2000) Bt Acres (000) Bales Lost Per Bt A 1 Total Bales Lost Total Loss 2 ($ 000/yr) AL 344 0 0 0 AZ 162 0 0 0 AR 570.0047 2679 772 CA 46 0 0 0 FL 80 0 0 0 GA 648 0 0 0 LA 563.0047 2646 762 MS 1024.0047 4813 1386 MO 85 0 0 0 NM 25 0 0 0 NC 379 0 0 0 OK 94.0047 442 127 SC 209 0 0 0 TN 429 0 0 0 TX 442.0047 2077 598 VA 44 0 0 0 Total 5144 12657 3645 1 Derived from [21] for AZ, LA, NC and TN. Assigned to neighboring states. 2 Calculated at $288/bale. 15
Table 33.10 Summary of Current Losses and Costs on Bt Cotton Acreage (BW/FAW/BAW/SL) BW (bales) Production Volume FAW/BAW/SL Total (bales) (000lbs) Production Value (000 $/yr.) BW FAW/BAW/SL Total AL 3818 0 1833 1099 0 1099 AZ 859 0 412 247 0 247 AR 6327 2679 4323 1822 772 2594 CA 244 0 117 70 0 70 FL 888 0 426 256 0 256 GA 7193 0 3453 2072 0 2072 LA 6249 2646 4270 1799 762 2561 MS 11366 4813 7766 3273 1386 4659 MO 1377 0 661 396 0 396 NM 132 0 63 38 0 38 NC 10271 0 4930 2958 0 2958 OK 498 442 451 143 127 270 SC 5664 0 2719 1631 0 1631 TN 6950 0 3336 2001 0 2001 TX 2343 2077 2122 675 598 1273 VA 1192 0 572 343 0 343 BW Sprays Spray Costs (000$) FAW/BAW/SL Sprays Pesticide Use (lbs. AI/yr) Total BW Sprays FAW/BAW/SL Sprays Total AL 45 103 148 1250 2961 4211 AZ 33 53 86 500 3384 3884 AR 5291 1927 7218 101750 62604 164354 CA 16 13 29 250 846 1096 FL 18-18 500-500 GA 1620 311 1931 40500 10998 51498 LA 2714 4067 6781 96375 190350 286725 MS 5067 2763 7830 95975 99405 195380 MO 8 33 41 250 1269 1519 NM 72 32 104 1000 846 1846 NC 2186-2186 66250-66250 OK 38 78 116 750 2115 2865 SC 2257-2257 64500-64500 TN 1437-1437 31750-31750 TX 580 2880 3460 13500 84177 97677 VA 554-554 12600-12600 16
Table 33.11 % Reduction of Larvae by Bt Cottons Bt Cotton I Bt Cotton II Bollworm 57.0 86.0 Tobacco Budworm 99.9 99.9 Soybean Looper 0 99.9 Fall Armyworm 20.0 87.0 Beet Armyworm 30.0 86.0 Source: [6]. Reductions are measured from the number of larvae found in a conventional cotton variety. Table 33.12 Potential Impacts of Adoption of Bt Cotton II 2 Bt Acres (000) Volume (000lbs) Value (000$) Production Sprays (000$) Costs Bt II 1 (000$) Net (000$) Net Income (000$) Pesticide Use Reduction (lbs/yr.) AL 344 1833 1099 148 688 +540 559 4211 AZ 162 412 247 86 324 +238 9 3884 AR 570 4323 2594 7218 1140-6078 8672 164354 CA 46 117 70 29 92 +63 7 1096 FL 80 426 256 18 160 +142 114 500 GA 648 3453 2072 1931 1296-635 2707 51498 LA 563 4270 2561 6781 1126-5655 8216 286725 MS 1024 7766 4659 7830 2048-5782 10441 195380 MO 85 661 396 41 170 +129 267 1519 NM 25 63 38 104 50-54 92 1846 NC 379 4930 2958 2186 758-1428 4386 66250 OK 94 451 270 116 188 +72 198 2865 SC 209 2719 1631 2257 418-1839 3470 64500 TN 429 3336 2001 1437 858-579 2580 31750 TX 442 2122 1273 3460 884-2576 3849 97677 VA 44 572 343 554 88-466 809 12600 Total 5144 37454 22468 34196 10288-23908 46376 986655 1 Calculated at $2.00/A 2 Data from Table 33.10 17
References: 1. Adamczyk, J. J., et al., Susceptibility of Conventional and Transgenic Cotton Bolls Expressing the Bacillus thuringiensis Cry1A(c) d-endotoxin to Fall Armyworm (Lepidoptera: Noctuidae) and Beet Armyworm (Lepidoptera: Noctuidae) Injury, Journal of Agricultural Entomology, 15(3): 163-171, July 1998. 2. Adamczyk, J. J., et al., Field Efficacy and Seasonal Expression Profiles for Terminal Leaves of Single and Double Bacillus thuringiensis Toxin Cotton Genotypes, Journal of Economic Entomology, 94(6): 1589-1593, 2001. 3. Stewart, S. D., et al., Impact of Bt Cottons Expressing One or Two Insecticidal Proteins of Bacillus thuringiensis Berliner on Growth and Survival of Noctuid (Lepidoptera) Larvae, Journal of Economic Entomology, 94(3): 752-760, 2001. 4. Gore, J., et al., Bollworm (Lepidoptera: Noctuidae) Survival on Bollgard and Bollgard II Cotton Flower Bud and Flower Components, Journal of Economic Entomology, 94(6): 1445-1451, 2001. 5. Jost, D. J., Bollgard II Cotton Efficacy Summary Southwest, 2001 Beltwide Cotton Conferences. 6. Adamczyk, J. J., et al., Evaluation of Bollgard II (CV. DP50BII) in the Mississippi Delta: Field Efficacy Against Various Lepidoptera While Profiling Season-Long Expression of Cry1A(c) and Cry2A(b), 2001 Beltwide Cotton Conferences. 7. Ridge, Rebecca, et al., Efficacy of Bollgard II as a Lepidopterous Larvicide in Cotton, 2001 Beltwide Cotton Conferences. 8. Akin, D. S., et al., Field Efficacy of Cotton Expressing Two Insecticidal Proteins of Bacillus thuringiensis, 2001 Beltwide Cotton Conferences. 9. Jackson, R. E., et al., Efficacy of Bollgard and Bollgard II Cottons Against Bollworm, Helicoverpa Zea (Boddie) in Field and Greenhouse Studies, 2001 Beltwide Cotton Conferences. 10. Marsh, B. H., et al., Bollgard II in the Southern San Joaquin Valley, 2001 Beltwide Cotton Conferences. 11. Lorenz, Gus, et al., Bollgard II Performance in Arkansas, 2001 Beltwide Cotton Conferences. 18
12. Allen, Charles T. and Marwan S. Karboutli, Effectiveness of Bollgard II Cotton Varieties Against Foliage and Fruit Feeding Caterpillars in Arkansas, 2000 Beltwide Cotton Conferences. 13. Pitts, D. L., Bollgard II Cotton Efficacy Summary Southeast, 2001 Beltwide Cotton Conferences. 14. Voth, R. D., Bollgard II Cotton Technical Review, 2001 Beltwide Cotton Conferences. 15. Norman, John W., et al., Performance of Bollgard II Cotton Against Lepidopterous Pests in the Lower Rio Grande Valley of Texas, 2001 Beltwide Cotton Conferences. 16. Rahn, P. R., et al., Efficacy and Agronomic Performance of Bollgard II, 2001 Beltwide Cotton Conferences. 17. Jackson, R. E., et al., Field and Greenhouse Performance of Bollworm on Bollgard II Cotton Genotypes, 2000 Beltwide Cotton Conferences. 18. Stewart, S. D. and K. S. Knighten, Efficacy of Bt Cotton Expressing Two Insecticidl Proteins of Bacillus thuringiensis Berliner on Selected Caterpillar Pests, 2000 Beltwide Cotton Conferences. 19. Greenplate, J. T., et al., Bollgard II Efficacy: Quantification of Total Lepidopteran Activity in a 2-Gene Product, 2000 Beltwide Cotton Conferences. 20. Ridge, R. L., et al., Field Comparison of Genetically-Modified Cottons Containing One Strain (Bollgard) and Two Strains (Bollgard II) of Bacillus thuringiensis kurstaki, 2000 Beltwide Cotton Conferences. 21. Williams, Michael R., Cotton Insect Losses, Beltwide Cotton Conferences, 1990-2001. 22. 2001 Alabama Pest Management Handbook, Extension Service, Clemson University. 23. USDA, Crop Production 2000 Summary, National Agricultural Statistics Service, January 2001. 24. USDA, Crop Values 2000 Summary, National Agricultural Statistics Service, February 2001. 19
25. USDA, Cotton Varieties Planted (Annual 1995-2000), Agricultural Marketing Service-Cotton Program, Memphis Tennessee. 26. Hardee, D. D., et al, Annual Conference Report on Cotton Insect Research and Control, Beltwide Cotton Conferences, 1995-2001. 27. Smith, H. and Barry L. Freeman, Fall Armyworms: Consistent Cotton Pests, Agricultural & Natural Resources Entomology, circular ANR-892. 28. Smith, Ronald H., Soybean Loopers: Late Season Foliage Feeders on Cotton, Alabama Cooperative Extension Service, June 1994. 29. Integrated Pest Management for Cotton in the Western Region of the United States, University of California, Division of Agriculture and Natural Resources, Publication 3305, 1984. 30. Smith, R. H., et al, Diseases, Parasites Help Control Beet Armyworms in Cotton, Highlights of Agricultural Research, Alabama Agricultural Experiment Station, Summer 1989. 31. Moulton, J. K., et al, Studies of Resistance of Beet Armyworm (Spodoptera Exigua) to Spinosad in Field Populations from the Southern USA and Southeast Asia, 1999 Beltwide Cotton Conferences. 32. A New Look at the Beet Armyworm, California-Arizona-Texas Cotton Magazine, April 1999. 20