Preliminary Evaluation of the “Next Generation” of Bt Cotton

The next generation of Bollgard cotton was evaluated for agronomic and insecticidal efficacy under central Arizona growing conditions. Two novel lines were compared with their recurrent parents, DP50 and DP50B. There were no seasonlong differences observed among the varieties in most plant development and insect parameters. However, DP50 had significantly lower emergence than the other lines tested (possibly related to seed quality). The lower plant population may have been responsible for greater whitefly abundance observed on two dates mid-season. During early-season ratings of secondary “pests” (15 DAP) (scaled on damage and/or presence), the two test lines received lower ratings for thrips and flea beetle when compared with DP50, DP50B and DP50Bu (untreated for Lepidoptera). However, these difference are likely as a result of the difference in seed treatments that the two test lines received (Gaucho) and the others did not. This seed treatment does have known activity against thrips and beetle pests. In mid-season, the two test lines received lower ratings for beet armyworm when compared to DP50, DP50B and DP50Bu (although, not significantly different from DP50B or DP50Bu). Efficacy against pink bollworm (PBW) was assessed one time at the end of the season (we were limited to this time, so as to not affect yield), and DP50 was the only variety in which PBW exit holes were observed and PBW larvae collected. However, the low Lepidoptera pressure experienced during the season limited assessments of the two novel lines’ efficacy toward PBW. There was no significant difference in yield (bale/A) among the varieties. Although, one of the test lines had a lower lint turnout than each other variety. The two novel Bollgard lines performed well under our growing conditions, but continued evaluations will be necessary under more conditions and more insect pressures before “varietal” performance and gene efficacy can be assessed adequately.