Seasonal pink bollworm, Pectinophora gossypiella (Saunders), infestations of transgenic and non-transgenic cottons

The susceptibility of pink bollworm (PBW), Pectinophora gossypiella (Saunders), larvae to NuCOTN 33B(infinity) (Bt) and Delta and Pineland (DPL) 5415 cotton, Gossypium hirsutum L., bells developing on early- and late-season plant nodes was studied. Bells were artificially infested with PEW eggs from a laboratory colony or exposed to feral PBW populations in the field. For artificial egg infestations, PEW entrance holes in Bt and DPL 5415 bells averaged 19.0 +/- 2.2 and 14.4 +/- 1.2 per bell, respectively, over seven sampling dates. No larval exit holes were found in Bt cotton bells, and an average of 1.8 +/- 0.2 exit holes per bell occurred in DPL 5415 cotton bells. Larval survival as percentages of the numbers of entrance holes were 21.5 for DPL 5415 and < 0.1 For Bt. The extremely low larval survival in Dt cotton from more that 11,000 entrance holes suggests, at least for the laboratory strain in this study, a high level of Bt susceptibility. Live and dead first instars in Bt bells ranged From < 0.1 to 2.1 per bell. No living or dead second- or third-instar larvae occurred. Seven surviving PEW (living fourth instars or pupae in bell boxes) were found in Bt bells over all sampling dates. All Fl larvae obtained fr om survivors in the putative Bt bulls died on Bt bulls, but 50% boil infestation with 0.6 larvae per boil occurred following release on DPL 5415 bells. No tests were conducted with Bt bells to verify the presence of Cry1Ac toxic protein bur the complete mortality of the Fl larvae suggests that the surviving larvae were from non-Bt bells. In contrast to Bt bells, no dead first instars, 0.0 to 0.1 live second instar, 0. 1 to 0.2 live third instar, and 0.6 to 5.5 live fourth instars were found per DPL 5415 boil Immature Bt cotton bells developing on plants 180 days after planting (DAP) were as toxic to PEW larvae as immature bells developing on plants 83 DAP. Random bull sampling in plots showed an average of 31 and < 1% bell infestations in DPL 5415 and Bt cottons, respectively. Average numbers of entrance holes per DPL 5415 and Bt cotton boil were 1.5 and 1.0, respectively. Percentages of surviving larvae were 21.2% for DPL 5415 and 0.7% for Bt. Whole cotton plant sampling showed PEW infestations of 17.2% of the open mature and 10.5% of the immature green bells For DPL 5415, and 0.0% of the open Bt bells infested Bt and 1.7% infested immature green bells. Briefly, our study showed that the Bt toxic protein technology continues to be outstanding in season-long effectiveness for PEW control. There were no indications of reduced efficacy for late-season bells.