• Looking for Functional Non-Target Differences Between Transgenic and Conventional Cottons: Implications for Biological Control

      Naranjo, Steven E.; Ellsworth, Peter C.; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ; University of Arizona, Maricopa, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2002-06)
      Evaluations of the non-target effects of transgenic cotton, modified to express the insecticidal proteins of Bacillus thuringiensis (Bt), have been underway in Arizona since 1999. Here we provide a preliminary report of replicated field studies conducted from 1999 to 2001 to examine comparative affects of Bt cotton on natural enemy abundance, overall arthropod diversity, and natural enemy function. Analyses completed to date indicate that natural enemy abundance and overall arthropod diversity are affected by use of additional insecticides for other pests, but not directly by transgenic cottons in comparison with non-transgenic cottons. Further studies suggest that natural enemy function, measured as rates of predation and parasitism on two key pests (Pectinophora gossypiella (Saunders) and Bemisia tabaci (Gennadius)) of cotton in the western U.S., is unaffected in Bt cotton. Our preliminary results suggest that use of transgenic cotton may not have any unintended effects and represents an extremely selective pest control method that could facilitate the broader use of biological control and IPM in an agricultural system long dominated by the use of broad-spectrum insecticides.
    • Pink Bollworm and Cabbage Looper Motalities and NuCOTN 33B (Bt) Cry1Ac Contents in Cotton Fruiting Forms and Leaves on Increasing Numbers of Days after Planning

      Henneberry, T. J.; Forlow Jech, L.; de la Torre, T.; Maurer, J.; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2002-06)
      Studies were conducted to follow seasonal susceptibility of feral pink bollworm (PBW), Pectinophora gossypiella (Saunders) larvae to NuCOTN 33B (Bt) and Deltapine (DPL) 5414 in furrow and furrow plus supplementary drip-irrigated cotton field plots. Laboratory bioassays of laboratory - reared PBW larvae to flower buds and bolls and cabbage looper (CL), Trichoplusia ni (Hübner), larval mortality feeding on DPL 5415 and Bt cottons leaves were also conducted. Cry1Ac insect toxic protein contents in the different plant tissue were determined by Enzyme Linked ImmunoSorbent Assay (ELISA) throughout the season to compare in relation to PBW and CL mortality data. Irrigation type had no effect on PBW or CL larval mortality parameters measured. DPL 5415 bolls had 0.15 feral live larvae per boll and no dead larvae per boll compared with no live and 0.12 dead feral larvae per Bt boll. Whole plant samples showed 0.5 to 8.6% live larvae boll infestations compared to no live PBW life stages and no exit holes for Bt bolls. No PBW larvae survived on day four following bioassay infestation of one-third grown Bt flower buds with PBW neonate larvae as compared to 90% larval survival on DPL 5415 flower buds. Immature bolls harvested in the field and artificially infested with PBW larvae in the laboratory showed averages of 3 to 52% live larvae per boll, all in fourth instar of development, for DPL 5415 bolls compared to no live larvae, no development beyond the first instar, and no exit holes for Bt bolls. Cry1Ac protein level in flower buds were 0.11 to 0.16 ppm and 0.14, 0.11 and 0.05 ppm, in each case, per wet weight gram of boll tissue in bolls during the season. For CL leaf bioassays, larval mortalities after 7 days feeding on Bt leaves were variable ranging from 82 to 94% from node 8 on 61 and 82 days after planting (DAP) to 32, 38 and 7% on leaves from node 16 on 82, 117, and 159 DAP, respectively, and 28 and 6% on leaves from node 24 on 117 and 159 DAP. Cry1Ac amounts were 0.96 and 0.85 ppm (wet wgt per g of Bt leaf tissue), from leaves from node 8 (61 and 82 DAP), 0.53, 0.50 and 0.22 ppm (node 16, 82, 117, and 159 DAP) and 0.44 and 0.18 ppm (node 24, 117 and 159 DAP). Numbers of cotton bolls, lint and seed per acre were significantly greater from plots that were furrow plus drip irrigated as compared to furrow irrigated alone. DPL 5415 and Bt cotton yields were not significantly different.
    • Pink Bollworm: Diapause Larval Exit from Harvested Immature Cotton Bolls and Percentages Surviving to Moth Emergence

      Henneberry, T. J.; Forlow Jech, L.; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2002-06)
      Pink bollworm (PBW), Pectinophora gossypiella (Saunders), diapause larval exit from immature green bolls and larval and pupal mortality after exiting bolls, were studied at Phoenix, AZ in the insectary. Diapause larvae exited immature bolls sporadically during January, February, and early March. Thereafter, exit from the bolls was more consistent and highest numbers emerged in late April, May or early June. Larval and pupal mortality were high during January to early February and March, decreased in mid-March through early June, and increased again in mid-June to early August. Larvae remained in immature bolls as long as 319 days after harvest. Moth emergence was significantly correlated to accumulated heat units (12.8 and 30.6°C lower and upper developmental thresholds).
    • Sweetpotato Whitefly Nymph Mortality and Adult and Nymph Honeydew Production Following Treatment with Applaud or Knack

      Henneberry, T. J.; Forlow Jech, L.; Hendrix, D. L.; de la Torre, T.; Maurer, J.; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2002-06)
      Cotton lint contamination from honeydew excreted by sweetpotato whiteflies, Bemisia tabaci (Gennadius), is a serious problem in the textile industry resulting in reduced lint processing efficiency. The insect growth regulators, Applaud® and Knack®, provide effective control of sweetpotato whiteflies on cotton by interfering with their reproduction and development. Protection from honeydew lint contamination is attributed to reduced sweetpotato whitefly populations. We investigated the potential direct effect of Applaud and Knack on sweetpotato whitefly honeydew production. In the field, amounts of the major sugar components of honeydew produced by adults and nymphs collected on day six following Applaud or Knack applications to cotton field plots were not significantly different compared to amounts produced by those collected from untreated plots. In the laboratory, adult mortality and amounts of honeydew sugars produced by adults were not affected by confinement for 48 h on Applaud or Knack residues from cotton leaf dips or following nebulizer contact spray applications. In contrast, mortality of first and second instar nymphs on leaves was higher on day six following leaf dips in Applaud solutions compared with leaf dips in Knack or water solutions. Nymph mortality on day six following leaf dips in Knack solutions was higher than mortality of nymphs following leaf dips in water. Honeydew collected during the period between two to 50 h after leaf dip treatment had reduced amounts of glucose, fructose and trehalulose, but not sucrose and melezitose per nymph compared with honeydew from nymphs on leaves dipped in water. Results were more variable for sugars in honeydew collected 96 to 144 h after leaf dip treatment. Nebulizer sprays of Applaud and Knack to nymphs on cotton leaves also resulted in reduced amounts of sugars in honeydew and nymph mortality following treatments.