• An Action Threshold for Management of Sweet Potato Whitefly in Cantaloupe

      Palumbo, J. C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      A range of action thresholds for the control of sweet potato whitefly, Bemisia tabaci Gennadius were evaluated in field experiments with high population density of B. tabaci. Action thresholds for whitefly adults, based on seasonal whitefly averages that could result in 5% and 15 % dollar losses, of 3 and 10 adults per leaf, respectively, were tested. All thresholds were compared to weekly insecticide treatments and an untreated check The resulting best threshold treatment was 3 adults per leaf area which provided a 170% increase in net return over the untreated check. The 3 adult per leaf threshold resulted in 6 applications of insecticide, compared with 10 applications used in the weekly regime.
    • Admire® Insecticide Use and Influence on Cantaloupe Growth

      Umeda, K.; Fredman, C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Cantaloupe growth was influenced by using imidacloprid (Admire®) insecticide to control, suppress, or reduce whiteflies. The growth rate of cantaloupe was evaluated at regular intervals after crop emergence and a rate response was observed with greater growth with respect to increase in Admire® rate. Following at planting time applications, at 3 and 4 weeks after treatment (WAT) cantaloupe plants had more foliar growth and a greater number of leaves with increasing Admire® rate. At 5 to 8 WAT, cantaloupe vines exhibited greater growth with increasing rates of Admire®.
    • Basal Crop Coefficients for Vegetables in Central Arizona

      Martin, E. C.; Slack, D. C.; Pegelow, E. J.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      The world supply of quality water for irrigation of crops is being depleted. Growers in the arid and semi-arid regions of the world, where irrigation is a requirement for crop production, are looking for ways to conserve their water use and increase their irrigation efficiency. One tool that has been useful in helping growers reduce their irrigation water inputs is computerized irrigation scheduling programs. This study is part of a joint project between the government of Egypt (National Agricultural Research Project), USA1D and The University of Arizona. Working together, researchers from Egypt and Arizona are developing water management tools that will help both countries better use their scarce water resources in arid environments. The main thrust of this segment of the project is to develop water use data on vegetables grown in both regions. These data will then be used to develop crop coefficient data to be used in AZSCHED, a computerized irrigation scheduling program developed at the University of Arizona. Using a subsurface drip irrigation (SDI) system, carrots, cauliflower, head lettuce, and tomatoes were grown to determine water use patterns and develop basal crop coefficients. Water use data were collected using a neutron moisture gauge and a time domain reflectometer (TDR). Soil water data were collected 1 day following an irrigation and just prior to the next irrigation. Additionally, three different watering regimens were employed using available water content in the rootzone as a trigger to initiate irrigation (20 %, 30% and 40% depletion). The carrots, cauliflower and lettuce were planted in early October, 1993, using a randomized block design. Yield data showed no significant differences between treatments for any of the vegetables. Also, the soil moisture data did not indicate water stress in the treatments. In March of 1994, tomato transplants were planted and the irrigation treatments were altered to 30 %, 40% and 50% depletion, in an attempt to get significant differences between treatments. The results for all four vegetables showed high variability in soil water data between replications, although an initial determination of basal crop coefficients was possible. Additional data will be required to better refine the crop coefficients.
    • Broccoli Variety Trials 1994/1995

      Wilson, Mark; Oebker, Norman F.; The Barkley Company (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
    • Cabbage Variety Trials 1994/1995

      Wilcox, Mark; Oebker, Norman F.; Yuma Valley Agricultural Center (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
    • Cauliflower Variety Trials 1994/1995

      Wilcox, Mark; Cuming, Jim; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
    • Comparative Efficacy of B.t. Insecticides Against Lepidopterous Pests in Cabbage

      Umeda, K.; Fredman, C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Several commercial formulations of Bacillus thuringiensis (Al) insecticides were applied on cabbage and lepidopterous pests including Tricoplusia it (cabbage looper, CL), Spodoptera exigua (beet armyworm, BAW), and Plutella xvlostella (diamondback moth, DBM) were effectively reduced in population. The ten commercial products did not appear to vary significantly in controlling CL, the dominant species present in the cabbage.
    • 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)
    • Dacthal® Herbicide Rate Comparison for Preemergence Weed Control in Onions

      Umeda, K.; Fredman, C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      DCPA (Dacthal®) herbicide was applied preemergence (PE) to the soil surface after onion planting and no crop injury was observed for rates of 5.3, 7.5, and 10.5 lb. a.i. /A at one of two locations. Dacthal® gave good control of London rocket and cheeseweed (90 -94 %) at one location and marginal control at the second location (79 -85 %). Dacthal® did not exhibit a rate response to control the two weeds common to both locations. The lower rate of Dacthal® did not differ in efficacy compared to higher rates to completely control lambsquarters and nettleleaf goosefoot. All rates of Dacthal® marginally controlled yellow sweetclover and other mustard weeds present. Dacthal® provided adequate weed control to allow onion stand establishment.
    • Dry Bulb Onion Variety Trial

      Umeda, K.; Fredman, C.; McGrath, B.; Pettigrew, T.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Forty-five different dry bulb onion varieties were grown and evaluated to provide a comparison of varietal characteristics including firmness, size, shape, and maturity.
    • Early Postemergence Herbicide Weed Control in Onions

      Umeda, K.; Fredman, C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Oxyfluorfen (Goal®) herbicide at 0.25 lb. ai./A and bromoxynil (Buctril®) at 0.38 lb.a.i. /A applied early postemergence (POST) to onions at the 1- to 2-leaf stage of growth gave near complete control ( >98 %) of lambsquarters, knotweed, cheeseweed, London rocket, and good control ( -90 %) of shepherd's purse. Buctril® did not control annual bluegrass and Goal® only slightly reduced some of the heavy population. Both herbicides caused marginally unacceptable onion injury at 17-20 %. Buctril® plus pendimethalin (Prowl®) tank-mix combination applied POST also gave very good broadleaaved weed control but annual bluegrass was reduced only 50 %. Similar onion injury was observed for the combination treatment as Buctril® alone. Buctril® caused onion injury when it was applied during cloudy weather. Buctril® and Goal® were effective for broadspectrum broadleaved weed control but onions were sensitive when treated before reaching the full 2-leaf stage of growth. Cloudy weather during applications also intensified the onion injury by Buctril® treatments.
    • Efficacy and Temporal Mortality of Selective Insecticides on Beet Armyworm Larvae in Lettuce

      Palumbo, J. C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
    • Efficacy of Biorational Insecticides to Beet Armyworm and Cabbage Looper on Iceberg Lettuce

      Kerns, David L.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Four tests were conducted evaluating biorational insecticides for control of beet armyworm (BAW) and cabbage looper (CL) on iceberg lettuce. Treatment means for BAW were difficult to separate due to low population densities. The new formulation of Javelin appeared to be the most efficacious Bt overall. However, when Bts were compared on a equal cost/A basis, there were no significant derences among products for CL control. All Bts were comparable to Lannate for CL control. The neem oil extract Align, provided adequate BAW and CL control, and its efficacy at low rates seemed to be slightly enhanced by the addition of Sunspray Ultrafine Oil. Larvin at lower than label recommended rates gave good BAW and CL control as did Javelin. The tank-mix of these two products did not enhance worm control over that of the products used alone. Mustang gave good control of CL but appeared to be slightly weak against BAW.
    • Efficacy of Insecticides to Green Peach Aphid on Iceberg Lettuce

      Kerns, David L.; Palumbo, John C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Three tests were conducted evaluating foliar and soil applied aphicides for efficacy to green peach aphid infesting iceberg lettuce. Aphid population densites were low in all three studies and differences among treatments were difficult to discern. At low aphid populations we could not detect whether or not soil applications of Admire enhanced or inhibited the activity of subsequent foliar applications of other aphicides. Although when used alone, some products did offer statistically significant aphid control. However, in a commercial setting these differences would probably not be significant. At low aphid populations none of the pyrethroid tank mixes evaluated gave significantly better aphid control than the products used alone. All of the experimental aphicides evaluated appeared to have some degree of efficacy to green peach aphid.
    • Evaluation of Admire Soil Treatments on Colonization of Green Peach Aphid and Marketability of Lettuce

      Palumbo, John; Kerns, David; Hannan, Todd; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Admire (imidacloprid), applied as a soil treatment, protected lettuce plants from developing infestations of green peach aphid, Myzus persicae (Sulzer), for 60-100 d after planting based on two small plot and two commercial field trials. Admire applied 7.6 cm sub-seed furrow provided longer and more consistent protection from green peach aphid than treatments applied to the soil surface, as a side-dress, or 15.2 cm sub-seed furrow. Surface band applications of Admire provided inconsistent control probably because of inadequate hydrological incorporation into the soil. In small plot trials, effective control of aphids by Admire applied 7.6 cm sub seed furrow resulted in greater than 90.0% marketable heads while the untreated plots contained 20.0% marketable heads. When used in a commercial setting, Admire applied 7.6 cm sub-seed furrow on leaf lettuce prevented aphid colonization (<3 aphids per plant) for approximately 100 d after planting, while the untreated and commercial standard treated areas contained 30.7 and 26.8 aphids per plant respectively at 100 d after planting. In addition, marketability of lettuce was greater in Admire treated plots. As a sub-seed furrow treatment, Admire provides a more suitable approach to aphid control than is currently available with foliar insecticides.
    • Field Evaluation of Potential New Fungicides for Control of Downy Mildew of Broccoli in 1994 and 1995

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Downy mildew of broccoli is caused by the plant pathogenic fungus Peronospora parasitica. Cool damp weather with high humidity is highly favorable for sporulation, dissemination of spores, and infection by this pathogen. The severity of disease is affected by the duration of weather conditions favorable for disease development. Potential new fungicides were evaluated for disease control in field trials conducted during 1994 and 1995. Downy mildew did not occur in the 1994 trial. In 1995, disease was moderate and all tested fungicides provided significant disease control compared to no treatment at all. Three new fungicides, Fluazinam, Dimethomorph, and ICIA-5504, show promise as potential new materials for control of downy mildew on broccoli.
    • Field Evaluation of Potential New Fungicides for Control of Lettuce Downey and Powdery Mildew in 1994 and 1995

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      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 control of these diseases during 1994 and 1995. In 1994, downy mildew did not occur in the test plots; however, powdery mildew was severe and was controlled most effectively by Microthiol. In the 1995 study, both downy and powdery mildew developed in the test plots. The highest level of downy mildew control was achieved with three experimental compounds, Fluazinam, Dimethomorph, and BAS-490. The most effective fungicides for control of powdery mildew in 1995 were BAS-490 and Microthiol.
    • Field Evaluation of Potential New Fungicides for Control of Powdery Mildew of Cantaloupe in 1994

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Powdery mildew of cantaloupe in Arizona is caused by the plant pathogenic fungus Sphaerotheca fuliginea. The disease is found in melon fields each year; however, the incidence and severity of the disease is quite variable. Disease development is favored by low relative humidity, moderate temperatures, and succulent plant growth. Potential new fungicides were evaluated for disease control in a field trial conducted in the spring of 1994. In this study, Rally and Reach provided the highest level of disease control and highest percentages of marketable fruit when compared to untreated cantaloupe plants.
    • Field Evaluation of Potential New Fungicides for Control of Sclerotinia Leaf Drop of Lettuce in 1994 and 1995

      Matheron, Michael E.; Misaghi, Iraj J.; Porchas, Martin; DeCianne, Dominic; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Leaf drop of lettuce is caused by the plant pathogenic fungi Sclerotinia minor and S. sclerotiorum. Cool and moist environmental conditions favor disease development. Potential new fungicides were evaluated in field trials for control of this disease in 1994 and 1995. In the 1994 trial, Fluazinam and Topsin M provided significant decrease of disease and significant increase inmarketable yield compared to no treatment in plots infested with Sclerotinia minor or S. sclerotiorum. In 1995, Fluazinam, Topsin M, and two compounds from Ciba significantly reduced disease caused by Sclerotinia minor and increased marketable yield of treated lettuce when compared to nontreated plots.
    • Herbicide Weed Control in Cantaloupes

      Umeda, K.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Preemergence herbicide treatments metolachlor (Dual®) and pendimethalin (Prowl®) gave better than acceptable weed control ( >85 %) of prostrate and tumble pigweeds, puncturevine, common purslane, and groundcherry in cantaloupes. Preplant incorporated treatments provided less than adequate control of pigweeds and groundcherry. Bentazon (Basagran®) applied postemergence gave good control of pigweeds but groundcherry control was marginal. Napropamide (Devrinol®), trifluralin (Treflan®), and DCPA (Dacthal (D) caused cantaloupe stand reduction and injury. Bensulide (Prefar®) and Basagran® were safe when applied on cantaloupes.