• Asparagus Response to Water and Nitrogen

      Roth, Robert L.; Gardner, Byrant R.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      The relationships of asparagus yields to varying levels of water and nitrogen were determined. Maxinuem yields of 345, 560 and 300 crates/acre were produced for asparagus crowns that were 3, 4 and 5 years old, respectively. A total seasonal water depletion rate of 98 inches was calculated for the fern growing season. Optimum nitrogen applications were estimated at approximately 350 -400 lb/ac.
    • Assessment of Virus Disease Incidence and Whitefly Population in an Isolated Agroecosystem in Central Arizona

      Brown, Judith K.; Easley, Jack R.; Poulos, Bonnie T.; Nelson, Merritt R.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      A survey study was undertaken to identify the plant viruses, to document the occurrence of virus diseases, and to document the seasonal population dynamics of insect vectors in a semi-isolated agricultural site in Central Arizona. A typical year-round cropping history at the site consists of cotton and seasonal sequences of vegetables. The most abundant insects caught using 24-hr exposures of yellow sticky traps were whiteflies (Trialeurodes abutilonea Haldeman and Bemisia tabaci Genn.) and the cotton (or melon) aphid (Aphis gossypii Glover). Of the three, only B. tabaci and A. gossvpii are recognized as virus vectors in Arizona. The most prevalent plant virus identified in vegetable crops and/or weeds was lettuce infectious yellows virus (LIYV), a whitefly-transmitted virus. The virus was detected in lettuce, (greenleaf, romaine, iceberg, red leaf) watermelon, cantaloupe, spinach, and cilantro. In addition, the watermelon curly mottle/squash leaf curl virus complex (WCMoV-SLCV), watermelon mosaic virus 2 (WMV-2) zucchini yellow mosaic virus (ZYMV), cucumber mosaic virus (CMV), and squash mosaic virus (SqMV) were identified in cucurbits at various times and locations throughout the season.
    • Bell Pepper Row Cover and Drip Irrigation Test

      Harper, Fred; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
    • Comparison of Two Sweet Corn Types for Field Quality Holding

      Oebker, Norman F.; White, Marcia; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
    • 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)
    • 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.
    • 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 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.
    • Enhanced Growth of Drip Irrigated Sweet Corn Using a Nitrification Inhibitor

      Doerge, Thomas A.; Tucker, Thomas C.; McCreary, Ted W.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      A field experiment using subsurface drip irrigation was conducted at the Maricopa Agricultural Center on a Casa Grande sandy loam to evaluate the effect of varying nitrogen rates on the growth and yield of 'Jubilee' sweet corn when applied with, and without the nitrification inhibitor, nitrapyrin (N-Serveᴿ). N treatments of 89, 134 and 2671bs. N/acre were applied as ammonium sulfate to one meter miniplots in three split applications between the V2 and the V10 growth stages. Individual N-Serveᴿ application rates were 0.5 lbs/acre. All solutions were applied through buried, perforated PVC tubing to simulate application through the buried drip irrigation system. The inclusion of N-Serveᴿ significantly increased dry matter accumulation, number of total ears and number of marketable ears /plant at all N levels. Plant tissue analysis suggested that enhanced uptake of ammonium -N as well as reduced leaching of nitrate-N contributed to this growth response to N- Serveᴿ.
    • Evaluation of Head Lettuce Varieties for Liriomyza trifolii Leafminer Populations

      Rethwisch, Michael D.; Butler, Marvin D.; Meadows, Mike; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
    • Honeydew Measles: A Potential Threat to Commercial Honeydew Production

      Brown, Paul; Gibson, Richard; Oebker, Norman; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      Measles of honeydew melons is not a common problem, but melon growers should be aware that it can cause severe economic damage, under the right environmental conditions. At least one Pinal County grower suffered significant loss during an outbreak of this disease in September 1987.
    • Improved Management Strategies from Basic Biology of Whiteflies

      Byrne, David N.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      A series of experiments has been conducted aimed at learning more about whitefly biology. We learned that: 1) whitefly eggs imbibe water from plant tissue; 2) the wax particles on exterior body surfaces may be antifungal; 3) mature lettuce is not a good host for whiteflies and; 4) there is a migrating morph. All these facts are of practical importance.
    • International Asparagus Cultivar Trial

      McGrady, John; Nelson, John; Nichols, Mike; Tilt, Phil; Hart, Garry; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
    • Leafminer Fly New to Arizona Spreads Across State, Causes Severe Damange to Lettuce

      Rethwisch, Michael D.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
    • Mid-fall Planted Lettuce Cultivar Trial at Yuma, 1988-89 Season

      Oebker, Norman F.; McGrady, John; Butler, Marvin; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
    • Nitrogen and Water Effects on the Growth, Yield and Quality of Drip Irrigated Sweet Corn

      Doerge, Thomas A.; Stroehlein, Jack L.; Tucker, Thomas C.; Fangmeier, Del D.; Oebker, Norman F.; McCreary, Ted W.; Husman, Steve H.; Lakatos, Eugene A.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      A complete factorial experiment using three nitrogen (44, 106 and 160 lbs N/acre) and three water rates (60, 100 and 130% consumptive use) examined the specific management criteria necessary for obtaining optimum yield and quality of drip -irrigated 'Jubilee' sweet coni. The crop was planted on I March and harvested on 10 June, with an 86 /50°F heat unit accumulation of 1738. When present, a nitrogen deficiency greatly decreased marketable yield, number of marketable ears/plant, mean ear weight, ear length and tip fill. Higher moisture rates generally had less effect on yield and quality than did N rates; however, increasing water rates significantly increased marketable yields and plant height, improved tip fill and lessened the occurrence of blank kernels. The effect of N and water rates on N and dry matter accumulation and on diagnostic plant tissue testing results for sweet corn are also presented. The maximum marketable yield obtained in this experiment was 7.8 tons per acre, using 160 lbs N/acre and 21.1 inches of irrigation water.
    • Oriental Vegetable Cultivar Trials

      McGrady, John; Tilt, Phil; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
    • Powdery Mildew of Cantaloupe -- Evaluation of New Fungicides for Disease Control

      Matheson, Michael E.; Matejka, Joseph C.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      Powdery mildew of cantaloupe, caused by Sphaerotheca fuliginea, is a perennial and often devastating disease in Arizona. During 1987 and 1984 potential new fungicides were evaluated in field trials for disease control. In 1987, Bayleton, Rally and Spotless provided significant disease control. In 1984, Rally and Spotless significantly reduced development of powdery mildew, while Bayleton and Tilt were less effective. Uneven development of powdery mildew within the plot may partially explain the apparent lack of significant disease control in 1988 by Bayleton and Tilt.
    • Resistance in Cultivated and Wild Lettuce to Lettuce Infectious Yellows Virus

      Ray, Dennis T.; McCreight, James D.; McGrady, John J.; Brown, Judith K.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      In 1988, Arizona's early- season lettuce crop was plagued by disease and insect problems, both intensified by unseasonably high temperatures. In the western Arizona production area, an epidemic of lettuce infectious yellows (LIY) resulted in serious economic losses to growers. The yellows disease is incited by the LIY virus (LIYV), a plant virus transmitted by the sweet potato whitefly [Bemisia tabaci (Gene.)]. Disease symptoms in lettuce include stunted growth, rolling yellowing and /or reddening of infected leaves; necrotic lesions appear at or near the leaf margins at latter stages of the disease. LIYV has a wide host range which increases the difficulty of isolating lettuce fields from LIYV infected or whitefly-infested fields; also, whiteflies are resistant to insecticides. Therefore, host-plant resistance appears to be the most promising means of reducing losses due to this disease. To initiate a breeding program, commercial lettuce cultivars and breeding lines (Lactuca sativa L.), and related, cross-breeding wild lettuce species (L. serriola L. and L. saligna L.) were screened for resistance to LIYV in the western Arizona production area using natural inoculation by residence whiteflies.
    • Sclerotinia Leaf Drop on Lettuce -- Evaluation of New Fungicides for Disease Control

      Matheson, Michael E.; Matejka, Joseph C.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
      Leaf drop of lettuce, caused by Sclerotinia sclerotiorum, is a sporadic, but destructive, disease in Arizona. Field trials were established during 1987 and 1988 to evaluate potential new fungicides for disease control. Ronilan and Rovral, the two materials currently registered for use on lettuce for Sclerotinia leaf drop, were consistently among the most effective fungicides for disease control. Levels of disease control equivalent to that provided by Rovral and Ronilan were observed with CGA-449, SC-0854 SDS-65311, Bay HWG 1608, and Spotless. These field tests have identified several potential new fungicides for control of leaf drop of lettuce caused by S. sclerotionan.