• Fungicides Evaluated for Control of Sclerotinia Leaf Drop of Lettuce in 1991 Field Test

      Pier, J. W.; Doerge, T. A.; McCreary, T.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Cauliflower Variety Trials 1990/1991

      Butler, Marvin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Effects of Insecticides on Leafminers, Liriomyza spp., and Associated Parasitoids on Spring Cantaloupes

      Palumbo, J. C.; Mullis, C. H. Jr.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      A study was conducted to determine the effects of repeated insecticide applications on leaf niner and parasitoid populations on spring melons. After four applications, none of the insecticides induced large build-ups of leafminer larvae. A new material, AC 303630, was very effective in maintaining low numbers of pupae. However, the results of this preliminary test indicate that all insecticides tested had a negative impact on the parasitoid population. In general, in the absence of insectcides, parasitoids were capable of maintaining L. sativae populations at low levels in the experimental plots.
    • 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.
    • Evaluation of Agri-Mek with Various Oils and Adjuvents for Control of Leafminers in Spring Head Lettuce

      Rethwisch, Michael D.; Meadows, Michael; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • 1991 Virus Survey of Cantaloupe in Yuma

      Butler, Marvin; Brooks, Dave; Watson, Mike; Oebker, Norman F.; University of Arizona; Pasquinelli Produce (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • UA Seedless Watermelton Cultivar Trial - 1991

      Oebker, M. F.; McCreary, T. W.; Roth, R. L.; Doerge, T. A.; Pier, J. W.; Gibson, R. D.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      Seedless watermelons have become an important commodity in Arizona. In 1991 16 cultivars were compared and evaluated at the Maricopa Agricultural Center. Tri-X 313 had overall good performance and remains the standard. Several other cultivars show promise.
    • Control of Thrips in Seed Onions and Resultant Seed Yields

      Rethwisch, Michael D.; Daily, Bill; Sanderson, David; McDaniel, Charles; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      Four insecticides were evaluated for their effect on onion seed production in Yuma County where two species on thrips (western flower and onion) were present in seed fields. Visual differences between treatments resultant from onion thrips damage was evident within 10 days after treatments were applied at flower opening. Lorsban, Ammo and Capture treatments provided control of onion thrips based on condition of seed heads. Only Ammo and Capture treatments increased seed yield as the Lorsban treatment was thought to repel bees which are needed for pollination. Pyrethroid treatments yielded 40% more than the untreated check. Damage from onion thrips to onion seed in Yuma County is conservatively calculated to currently be at least $1.1 million annually.
    • Experimental Use of Beescent® to Influence Honey Bee Visitation to Watermelon

      Loper, Gerald M.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      A commercial product called Beescent® containing a mixture of chemicals including chemicals used by honey bees as pheromones, was applied to watermelons in early bloom on Aug. 15, 1991. Honey bee visitation to treated, 18-row plots, were significantly higher than to untreated for only 2 days, the day of treatment and the next day. Watermelon yields were not effected. The daily high temperatures reached 86-88 °F, so that most of the chemical had volatilized away by the end of the first day.
    • Nitrogen Management in Drip Irrigated Leaf Lettuce, Spinach and Green Crops

      Doerge, Thomas A.; Pritchard, Kevin H.; McCreary, Ted W.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      Preliminary nitrogen (N) management experiments with spinach, leaf lettuce, romaine collard and mustard were conducted on a Casa Grande s.l. soil at the Maricopa Agricultural Center in the winter and spring of 1990-91. The purpose of this N rate experiment was to develop initial Best Management strategies for N fertilizer use for emerging high value crops grown in Arizona using subsurface drip irrigation. Three rates of urea, ammonium nitrate were applied to each cultivar to provide deficient (N1), adequate (N2) and supraoptimal real (N3) levels of N. All cultivars responded dramatically to the application of N. Fresh weight yields in the N1 and N2 treatments averaged 45 and 53% of the N3 treatment The average N3 yields recorded in these trials were 23.1, 12.8 and 21.8 tons of marketable produce per acre for greens, spinach and leaf lettuce/romaine crops, respectively. Preliminary plant tissue test results indicated that for all five crops, whole plant total N (TN) levels and midrib + petiole NO₃-N and leaf blade TN concentrations in the youngest mature leaf were responsive to differences in soil N supply and show promise as diagnostic N tissue test procedures. The midrib + petiole NO₃-N test appeared to be the best indicator of plant N status throughout the growing season for all five crops studied.
    • Dry Matter Partitioning of Cowpea (Vigna Unguiculata (L.) Walp.) Under Water Deficit Conditions

      Neto, Manoel C.; Bartels, Paul G.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      Water Stress caused reduction of seed yield in cowpea plants by decreasing total biomass and photosynthesis. The source leaf, pod and seed water potential of stressed cowpea were lower than water potential in non-stressed plants. No differences in water potential and turgor were observed between pod walls and seed of cowpea plants. Partitioning of the total above ground dry matter was similar for both stressed and nonstressed cowpea plants. Photosynthetic rates of single leaves from cowpea were greater for nonstressed than stressed plants. The duration of seed growth of cowpea was not different between stressed and nonstressed plants; however, rate of seed growth at the end of seed filling period was greater in nonstressed plants. Seed growth rate of both stressed and nonstressed cowpea plants declined at about the same time photosynthesis of the source leaf declined. Leaf area index was greatest in nonstressed cowpea.
    • Fungicides Evaluated for Control of Rhizoctonia Bottom Rot of Lettuce in 1991 Field Trials

      Matheron, M. E.; Leonard, R.; Major, G.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      Bottom rot of lettuce, caused by the soil -borne fungus Rhizoctonia solani, can cause economic losses on early season lettuce harvested in November. First evidence of the disease is the appearance of brown, sunken, necrotic areas on the midribs of leaves touching the soil. Under favorable environmental conditions, the pathogen grows from leaf to leaf inside the head. If the fungus invades the leaves of the marketable head it and all similarly infected heads are left in the field resulting in economic losses. Field trials were established to evaluate the potential level of disease control obtainable by applying Ronilan or Rovral to lettuce beds immediately after thinning. No significant reduction in loss of marketable heads was observed in these trials, although there was a trend toward lower levels of bottom rot when either fungicide was in place.
    • Evaluation of Oils and Insecticides for Leafminer Control in La Paz County Snap Beans

      Rethwisch, Michael D.; Meadows, Michael; Hood, Larry; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Effectiveness of Oils in Water for Leafminer Control in Fall Head Lettuce

      Rethwisch, Michael D.; Hood, Larry; Meadows, Mike; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Effects of Lettuce Insecticides Applied at Planting

      Rethwisch, Michael D.; Meadows, Michael; Hagerman, Shari; Thiessen, James; McGrady, John; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Fungicides Evaluated for Control of Powdery Mildew of Cantaloupe in 1991 Field Trial

      Matheron, M. E.; Matejka, J. C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      Leaf drop of lettuce, caused by the plant pathogenic fungi Sclerotinia sclerotiorum and S. minor. occurs every year in some lettuce fields in Arizona. When environmental conditions are favorable, disease incidence and resulting crop loss can be significant. During the 1990-1991 lettuce season in western Arizona, different fungicides and rates of materials were evaluated in the field for disease control. All tested materials increased yields compared to not using any fungicide for disease control.
    • Optimizing Nitrogen and Water Inputs for Trickle Irrigated Watermelons

      Pier, J. W.; Doerge, T. A.; McCreary, T.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      Rising water costs and concern for groundwater contamination are driving growers to improve irrigation and fertilization efficiency. A tentative Best Management Practice (BMP) for nitrogen fertilization of watermelon, a high water and nitrogen fertilizer use crop, has been developed, but needs further field verification. Information from tensiometers is used to schedule irrigations and watermelon petiole nitrate levels at critical growth stages are used to recommend rates of nitrogen fertilizer to apply with the objective of producing economic yields while limiting conditions which favor nitrate leaching to groundwater. In 1991, a field experiment consisting of a complete 3x4 factorial arrangement of soil moisture tensions, -12, -7 and -4 kPa, and 60, 214 315 and 500 kg N/ha, respectively, applied through a subsurface trickle irrigation system to watermelon was conducted on a Casa Grande sandy loam at the Maricopa Agricultural Center. Petioles were sampled from the youngest mature leaf beginning at the 3-4 leaf stage and then at major growth stages until first harvest. Harvested melons were weighed and soluble solids, dry matter and N uptake were determined on two representative melons from each experimental unit. An estimate of vine dry matter and N uptake was also determined. Soil samples were taken at 30 cm depth intervals to 1.2 m and analyzed for extractable N. A trench profile method was used to determine root distribution patterns for the three soil moisture treatments receiving optimum N. Petiole nitrate levels were highly responsive to N fertilizer treatments and accurately quantified visual observations of crop N status. Petiole nitrate results also indicated that the preliminary tissue nitrate test was adequate in assisting with a nitrogen management program though minor modifications were necessary. Marketable yield showed a tension x N interaction with a ridge of maximum yield occurring from high soil water tension and low N to low soil water tension and high N with yield reductions on either side of the ridge. Yield estimates along the ridge ranged from 101 Mg/ha (45.4 ton /ac) at -8 kPa tension and 280 kg N/ha to 105 Mg/ha (47.3 ton /ac) at -4.4 kPa tension and 376 kg N/ha. A cost return analysis determined that maximum economic returns were $12,059/ha when 311 kg N/ha were applied in conjunction with -6 kPa soil tension (145 cm water). Unaccounted for N, as determined by an N balance method indicated large amounts of N were unaccounted for when high rates of N were applied under wet soil conditions. N loss was concluded to be due to either leaching and/or denitrification under these conditions.
    • Comparison of Capture, Capture and Thiodan, Malathion and Pounce Insecticides for Control of Two Aphid Species on Broccoli Seed

      Rethwisch, Michael D.; McDaniel, Charles W.; Major, Gary; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Broccoli Variety Trials 1990/1991

      Butler, Marvin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Effect of Insecticides on Sweetpotato Whitefly Numbers and Growth of Broccoli

      Rethwisch, Michael D.; McDaniel, Charles W.; Shaw, Mary; Theissen, James; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
      Eleven treatments were applied for sweetpotato whitefly B- biotype control. Best control (62.4%) was evidenced by the Ambush + Thiodan treatment, which had fewest nymph numbers 8 days post treatment and had larger plant sizes (46.3%) 14 days post treatment than the untreated check. Plants in plots receiving treatments including Thiodan and/or Lorsban were also at least 20% larger than the untreated check. Fewest number of adult whiteflies two days post treatments were noted in the Thiodan + M-Pede treatment. Certain treatments increased whitefly numbers.