• Performance of Products for Management of Sclerotinia Leaf Drop of Lettuce in 2002

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002-08)
      Sclerotinia leaf drop in Arizona is caused by two soil-borne fungi, Sclerotinia minor and S. sclerotiorum. Moist soil and moderate temperature favor this disease. Some new products in development were evaluated for control of leaf drop on lettuce during the winter vegetable growing season of 2001-2002. Sclerotia of each pathogen were applied to plots after thinning and just before the first of two applications of test compounds. Significant reduction of Sclerotinia leaf drop caused by S. minor occurred in plots treated with Endura, whereas other products tested against this pathogen did not significantly reduce the level of disease compared to nontreated control plants. The highest level of disease reduction in plots infested by S. sclerotiorum was achieved by the fungicide Ronilan as well as the biological material Contans. Somewhat lower but still significant disease control was achieved with Endura on plots infested with S. sclerotiorum. In this field trial, Endura provided the best level of disease control in plots infested with S. minor, whereas Contans provided the best level of disease control in plots infested with S. sclerotiorum.
    • Population Growth of Lettuce, Nasonovia ribisnigris, on Resistant Butter and Head Lettuce Cultivars

      Palumbo, John C.; Hannan, Todd A.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002-08)
      Studies to examine lettuce aphid population growth on resistant head and butter lettuce cultivars were conducted in small filed plots at the Yuma Agricultural Center. By artificially infesting plants on several lettuce plantings during the spring, the influence of the resistant lettuce plants were evaluated for their capability of preventing lettuce aphid populations from colonizing plants. Results of five field trials showed that several varieties of head and butter lettuce have been developed that almost completely prevent lettuce aphids from surviving and reproducing on plants during the spring. Although the cultivars tested did not posses marketable characteristic for harvests, they do provide germplasm for breeding new varieties suited for desert production. In addition, these studies also support conclusions drawn from the past several seasons that suggest lettuce aphid population growth is greatest when ambient temperatures average between 65-70 °F.
    • Evaluation of New Preemergence Herbicides Alone and in Combinations for Weed Control in Melons

      Umeda, Kai; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002-08)
      Azafenidin (Milestone®, Dupont) and flumioxazin (Valor®, Valent)) caused cantaloupe injury that was very marginal between acceptable (<15%) and unacceptable (>15%). Flufenacet (Bayer), isoxaben (Gallery, DowAgroSciences), and thifensulfuron (Harmony®, Dupont) at the rates tested caused severe crop injury. Isoxaben provided very good weed control (>90%), azafenidin provided acceptable control of only lambsquarters at 88% and less than acceptable (85%) control of pigweeds, purslane, and grasses, and flumioxazin at the higher rate of 0.05 lb AI/A tended to offer slightly better weed control than the lower rate but overall it was marginally acceptable. Bensulide (Prefar®) combined with flumioxazin caused negligible crop phytotoxicity and better than 93% control for purslane, pigweeds, lambsquarters, and grasses. Combinations of herbicides offered slightly improved weed control compared to herbicides applied alone. Crop injury increased for combinations with dimethenamid (Outlook®, Frontier®, BASF) and s-metolachlor (Dual Magnum®, Syngenta).