Submitted to: Southwest Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 1996
Publication Date: N/A
Interpretive Summary: Genetically modified cotton plants containing a gene for control of moth pests (BollgardTM gene, Monsanto Co.) will be commercially available to growers during the 1996 season. Seed for sale in 1996 was produced by growers under contract in Arizona in 1995. We examined bolls from these contract fields for infestation by the pink bollworm, a key cotton pest throughout the world. Our objectives were to see how effective the incorporated gene was and to provide baseline data for future comparisons of effectiveness. In this study we examined a total of 78,240 cotton bolls collected from 15 fields each of the genetically modified cotton and its unmodified parental stock. We found a total of 4711 pink bollworm larvae in the unmodified cotton bolls and 11 larvae in the genetically modified cotton bolls. This level of control is unattainable under conventional insecticidal control practices. Whether the pink bollworm is able to overcome the effects of the gene and become resistant to its effects will be determined from comparisons of this data and data from subsequent years.
Bolls from transgenic cotton, NuCOTN 33 (Delta and Pine Land Co.) containing the BollgardTM gene (Monsanto Co.) and from the parental cultivar DPL-5415 were examined for fourth (last) instar larvae of the pink bollworm (78,240 total bolls). Bolls from five paired fields were collected in the Queen Creek, Buckeye, and Gila Bend, AZ areas and a composite of 10 fields of each cultivar were collected in the Paloma Ranch area near Gila Bend, AZ. Collections of 100 or 80 bolls per field were made weekly from July through November, 1995. Numbers of pink bollworm larvae were very low in all fields through August and thereafter increased steadily in the control fields. Numbers of fourth instar larvae found in transgenic cotton were extremely low or non-existent throughout the season, even in fields which were adjacent to heavily infested control fields. These results show that NuCOTN 33 retained a high degree of efficacy for preventing the development of fourth instar pink bollworm larvae late in the season into diapause. Most important, these data provide baseline information against which efficacy in subsequent years can be compared.