Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2001
Publication Date: July 1, 2001
Technical Abstract: Studies were conducted in Phoenix, AZ cotton plots to evaluate the efficacy of NuCOTN 33B (Bt) (Monsanto Co., St. Louis, MO) for pink bollworm (PBW), Pectinophora gossypiella (Saunders), control in the field and to define the relationship between numbers of days of PBW larval feeding on bolls and mortality. We also determined, in the laboratory, larval mortality of cabbage looper, Trichoplusia ni (Hubner), beet armyworm, Spodoptera exigua (Hubner), and tobacco budworm, Heliothis virescens (F.) feeding on Bt cotton. For PBW, over 80 and 2 percent of DPL 5415 and Bt cotton bolls, respectively, were found with live PBW larvae after artificial egg infestations. Less than 0.02 of the live larvae per Bt boll developed to the last instar compared to 2.7 larvae per boll developing to the last instar for DPL 5415 bolls. In another experiment, no first instar PBW survived after feeding for more than 48 h on Bt bolls compared to an average of 1.5 larvae per boll surviving in DPL 5415 for feeding periods o 8 days. Tobacco budworm larvae were highly susceptible to Bt cotton; none survived greater than 3-day feeding periods on Bt cotton leaves. Beet armyworm and cabbage looper were less susceptible with 84, 68 and 47% of the beet armyworm and 100, 38, and 0% of the cabbage looper larvae, respectively, surviving 3, 6, or 9 days feeding on Bt leaves.