• Effect of Agronomix on Crisphead Lettuce at Yuma - 1992

      Oebker, N. F.; Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1994-09)
    • Evaluation of Foliar Applied Nutritional Mixes on Crisphead Lettuce for Yield, Quality and Incidence of Tipburn

      Wilcox, M.; Sanchez, C. A.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1994-09)
    • Field Testing of Potential New Fungicides for Control of Lettuce Diseases, 1993

      Matheron, M. E.; Matejka, J. C.; Porchas, M.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1994-09)
      Several diseases caused by plant pathogenic fungi can cause economic losses to lettuce growers in Arizona. Leaf drop of lettuce is caused by Sclerotinia minor and S. sclerotiorum, while downy and powdery mildew are caused by Bremia lactucae and Erysiphe cichoracearum, respectively. Cool and moist environmental conditions favor development of leaf drop and downy mildew, while warmer and dry weather is conducive for development of powdery mildew. Potential new fungicides were evaluated for control of these diseases during the winter of 1992-93. For leaf drop, two nonregistered materials, Fluazinam and Topsin M, controlled disease at least well as the standard registered fungicides. Fluazinam and Aliette provided equivalent control of downy mildew, while Fluazinam but not Aliene significantly reduced the severity of powdery mildew on lettuce.
    • The Response of Leaf Lettuce to Phosphorous Fertilizer Placement and Rate

      Pritchard, Kevin H.; Doerge, Thomas A.; McCreary, Ted W.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1994-09)
      A one-year field study was conducted at the Maricopa Agricultural Center in the winter and spring of 1991-92 with the purpose of comparing the response of leaf lettuce grown with subsurface drip irrigation to various broadcast and banded phosphorus (P) fertilizer applications and rates. Two rates of banded treble superphosphate, 250 lbs. (1X) and 125 lbs. (1/2X) of P2Osper acre, were applied immediately before planting in a concentrated strip 1 inch directly below the row to be seeded. One broadcast rate, 250 lbs. (1X) of P205 per acre of the same material, was applied and folded into the planting beds during listing. Control plots, in which zero P fertilizer was applied, were also maintained. Whole plant total P concentrations were higher in the first one-third of the growing season for the band treatments, though the differences in responses between band and broadcast applications were not statistically significant in the final third of the season. The 1X band treatment exhibited both greater plant heights and diameters than all other treatments during the first one-half of the growing season, and maintained greater height dimensions in the second half. The 1X broadcast and 1/2X band treatments exhibited similar growth throughout the season. By harvest there were not significant differences in head or plant size or in marketable yield among the three P treatments.