• Biochemical Studies of Rib Discoloration and Pink Rib of Lettuce

      Sharples, G. C. (College of Agriculture, University of Arizona (Tucson, AZ), 1965-08)
    • Characteristics of Harvested Lettuce Heads

      Oebker, N. F.; Hariott, B. L.; Page, Carmy G.; Foerman, B. R.; Grounds, R. E. (College of Agriculture, University of Arizona (Tucson, AZ), 1965-08)
      A study was made of the characteristics of harvested lettuce heads in Arizona during the 1964-65 season. Information on size, weight, firmness and number of wrapper leaves of each head sampled was collected and set up for analysis. No results were available at the time of this progress report.
    • Commercial Evaluation of Confirm for Control of Lepidopterous Pests of Lettuce using Various Applications Techniques

      Kerns, David L.; Tellez, Tony; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Confirm was evaluated in head lettuce for control of lepidopterous pests when applied by air, and when applied by ground at 4, 8 and 12 mph. By air Confirm may not provide commercially acceptable control when used alone. Confirm must be ingested to exhibit activity and aerial applications may not provide adequate spray coverage. When used by ground, applicators should avoid exceeding 8 mph, again because good spray coverage may be compromised.
    • Commercial Evaluation of Proclaim for Control of Lepidopterous Pests of Lettuce

      Tellez, Tony; Kerns, David L.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Proclaim 1.6 was evaluated in head lettuce in side-by-side large plot aerial and ground application demonstrations compared to commercial standard treatments. Proclaim consistently provided excellent control of beet armyworm and cabbage looper larvae. Worm control by Proclaim was equivalent to, or better than the commercial standards.
    • Commercial Field Performance of Confirm and Success on Head Lettuce and Broccoli

      Palumbo, John C.; Hannan, Todd A.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1999-02)
      Field trials were conducted in the Yuma and Gila Valleys to assess the commercial field performance of Confirm and Success insecticides against beet armyworm and cabbage looper larvae. Ten lettuce and five broccoli fields were treated with combinations of Confirm, Success, and standard insecticides on various stages of plant growth. Success provided quick knockdown of larvae, but ultimately Confirm provided equitable control. Cabbage looper control with Confirm appeared to be influence by application volume and plant size. Addition of pyrethroid to Confirm did not provide additional efficacy. Success provided good suppression of leafminer adults and thrips. Both products provided control equal to conventional standards and will become valuable components of future lettuce pest management programs in Arizona.
    • Comparative Effectiveness of Bacillus thuringiensis Formulations Against Lepidopterous Pests of Fall Lettuce

      Palumbo, J. C.; Mullis, C. H. Jr.; Reyes, F. J.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      A field study was conducted at Yuma in 1991 to examine the relative effectiveness of several formulations of Bacillus thuringiensis on beet armyworm and cabbage looper on seedling and pre-cupping lettuce. Several applications were made before and after thinning. Results of the study suggest that most formulations are capable of controlling small larvae. However, because of the inherent variation in beet armyworm dispersion, it was difficult to statistically attribute differences in pest levels due to insecticide efficacy.
    • Comparison of Alternative Management Approaches for Lepidopterous Larvae in Fall Lettuce

      Palumbo, John; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1999-02)
      For the second year, a large block experiment was conducted at the Yuma Ag Center to compare the field performance of three lettuce management programs for control of lepidopterous larvae. Conventional, experimental and biorational insecticides were sprayed to control beet armyworm, cabbage looper and Heliothis species throughout the growing season. Differences in populations of total larvae among the four treatments, relative to insecticide treatments and timing of application were observed throughout the season. In general, the standard and experimental treatments provided the most consistent control of lepidopterous larvae following each application. Harvest data showed that the spray regimes had a significant influence of head lettuce yield or quality. Maturity and quality were significantly reduced in the untreated control. An economic analysis shows that net returns varied widely among the management programs at different market prices. In conclusion, this study provides preliminary data to support the need for more development of experimental and biorational insecticide products as alternatives to conventional management programs in desert lettuce production.
    • Control of Liriomyza trifolii in Head Lettuce

      Rethwisch, Michael D.; Oebker, Norman F.; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1990-05)
    • Control of Liriomyza trifolii Larvae in Head Lettuce

      Rethwisch, Michael D.; Winans, S. Sherwood; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
    • Crisphead Lettuce Variety Trials 1994/1995

      Wilcox, Mark; Oebker, Norman F.; Yuma Valley Agricultural Center (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
    • Crisphead Lettuce Variety Trials 1995/96

      Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
    • Cultural Alternative for Avoidance of Lettuce Infectious Yellows Virus (LIYV)

      McGrady, John; Rubatzky, Vince; Oebker, Norm; Hartz, Tim; Butler, Marvin; Tilt, Phil; Hagerman, Sherry; Oebker, Norman F.; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1991-05)
    • Detection of Lettuce Infectious Yellow Virus (LIYV) in Greenhouse and Field Inoculated Plots Using an Indirect Enzyme-linked Immunosorbent Assay (Indirect ELISA)

      Brown, Judith K.; Poulos, Bonnie T.; Costa, Heather S.; Nelson, Merritt R.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      Lettuce infectious yellows virus (LIYV), a recently recognized plant virus, causes dramatic yellowing symptoms and severe diseases in a wide range of vegetable crops in Arizona, adjacent southwestern states and Mexico. Until now, the only available diagnostic method was a time-consuming bioassay that used the insect vector to transmit the virus, with subsequent manipulation of indicator plants. A rapid, sensitive diagnostic technique (termed an indirect enzyme-linked immunoassay, called indirect ELISA) system was developed to detect lettuce infectious yellows virus (LIYV) in infected plant material. A virus specific antibody was made to viral capsid protein which was purified by polyacrylamide gel electrophoresis. The indirect ELISA system was optimized and used to detect viral antigen in greenhouse-inoculated melons. The system was subsequently adapted to detect LIYV in symptomatic and asymptomatic weed and cultivated plant species collected from infected fields near Yuma and in central Arizona. The indirect ELISA system described here allows for the detection of approximately 100 ng of virus per well. The LIYV was detectable in symptomatic (but not in asymptomatic) leaves of melon plants infected with the virus. In contrast, the virus could be detected in both symptomatic and symptomless cheeseweed plants collected in the field. The optical density readings for infected weed species were generally lower than those for cultivated species, such as melons, lettuce, and spinach, suggesting that there is less virus in the weed hosts tested than in infected, cultivated hosts.
    • Downy and Powdery Mildew of Lettuce: Comparison of Chemical Management Tools in 1997

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Downy and powdery mildew are caused by the plant pathogenic fungi Bremia lactucae and Erysiphe cichoracearum, respectively. Cool and moist environmental conditions favor development of downy mildew, while warmer and dry weather is conducive for development of powdery mildew. Potential new fungicides were evaluated for management of these diseases in 1997. A very low level of downy mildew occurred during this trial; however, all treatments significantly reduced the number of leaf lesions compared to nontreated lettuce plants. Powdery mildew was quite intense at crop maturity and was significantly lower, compared to nontreated lettuce, on plants treated with Microthiol Special, BAS 490 + Bravo Weather Stik, Quadris, and two additional treatments not usually found to reduce this disease.
    • Early Fall Lettuce Cultivar Trials in Western Arizona, 1988

      Oebker, Norman F.; Winans, Sherwood; Butler, Marvin; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
    • 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)
    • Effect of Fertilizers on Yield, Quality and Nutrient Uptake by Lettuce

      Strohlein, J. L.; Tucker, T. C. (College of Agriculture, University of Arizona (Tucson, AZ), 1965-08)
      A series of studies on lettuce fertilization have been carried out over the past few years. Fertilizer applications increased yield through increased head size and did not affect the number or quality of harvested heads. The lower rates used were as effective as the higher rates. Nitrogen and phosphorus fertilization generally increased the nitrate and phosphorus content of the various plant parts selected for analysis.
    • Effect of Fungicides Applied at Different Rates on Control of Sclerotinia Leaf Drop of Lettuce -- 1990 Field Test

      Matheron, M. E.; Matejka, J. C.; Oebker, Norman F.; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1991-05)
      Leaf drop of lettuce, caused by the plant pathogenic fungi Sclerotinia sclerotiorum and S. minor, is found every year in some lettuce fields in Arizona. When environmental conditions are favorable, disease incidence and resulting crop loss can be significant. During the 1989 -90 lettuce season in western Arizona, different fungicides and rates of materials were evaluated in the field for disease control Ronilan and Rovral, the two fungicides currently registered for use on lettuce for control of Sclerotinia leaf drop, provided significant disease suppression and increased yields at all rates tested. Bravo and Botran did not control the disease.
    • Effect of Gypsum on Lettuce in Marana, 1988

      Thacker, Gary W.; Doerge, Thomas A.; Oebker, Norman P.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      Gypsum was applied preplant on spring lettuce at rates of zero, 2 tons per acre, and 4 tons per acre. There were no significant differences in carton yields or in carton weights. Postharvest soil analyses showed that the application of four tons of gypsum per acre significantly increased the calcium and magnesium levels in the saturated paste solution. There were no significant effects of gypsum application on ESP and SAR values, nor in pH or sodium concentrations.
    • Effect of Oil Treatments on Head Lettuce Photosynthesis and Growth

      Rethwisch, Michael D.; McGrady, John; Main, Greg; Coates, Wayne; Meadows, Mike; McDaniel, Charles; Shaw, Mary; Thiessen, James; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)