• Preemergence Herbicide Weed Control in Spinach

      Umeda, K.; Fredman, C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Two field studies were conducted to evaluate metolachlor (Dual®) for preemergence weed control in spinach to provide support to gain registration through the IR-4 program. Dual® at 1.0 to 1.5 lb a.i./A gave acceptable control of London rocket, black mustard, lambsquarters, and knotweed. Nettleleaf goosefoot, cheeseweed, and yellow sweetclover control was not acceptable. In one test, dimethenamid (Frontier® or SAN -582H, Sandoz) controlled London rocket, lambsquarters, knotweed, and goosefoot at 0.25 lb ai. /A and did not control cheeseweed or sweetclover. Spinach was not injured by Dual® or Frontier®.
    • Postemergence 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 0.125 to 0.25 lb. a.i./A applied postemergence (POST) to onions at the 3-leaf stage of growth effectively controlled London rocket, yellow sweetclover, and prostrate pigweed with marginal injury to onions. Earlier POST applications on 1- and 2-leaf onions caused injury and some stand reduction. Bromoxynil (Buctril®) herbicide at 0.25 lb. a.i./A applied early POST gave generally good weed control but did not adequately control sweetclover. Buctril® applied in clear weather did not injure 1-leaf onions but caused severe injury on 2- and 3-leaf onions when applied during cloudy weather conditions. Buctril® plus pendimethalin (Prowl®) tank-mix combination applied POST provided good control of London rocket, sweetclover, and prostrate pigweed; however, onion injury was severe due to applying Buctril® in cloudy weather. Buctril® and Goal® effectively controlled weeds present in the onions but timing of POST applications was critical with respect to onion size and weather conditions to minimize injury.
    • 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.
    • Imidacloprid Does Not Enhance Growth and Yield of Cantaloupe in the Absence of Whitefly

      Palumbo, J. C.; Sanchez, C. A.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Imidacloprid is a new, chloronicotinyl insecticide currently being used to control sweetpotato whitefly (Bemisia tabaci Genn, also known as silverleaf whitefly, Bemisia argentifolii Bellows and Perring). Large growth and yield increases of cantaloupes (Cucumis melo L.) following the use of imidacloprid have caused some to speculate that this compound may enhance growth and yield above that expected from insect control alone. Greenhouse and field studies were conducted to evaluate the growth and yield response of melons to imidacloprid in the presence and absence of whitefly pressure. In greenhouse cage studies, sweetpotato whiteflies developed very high densities of nymphs and eclosed pupal cases on plants not treated with imidacloprid, and significant increases in vegetative plant growth were inversely proportional to whitefly densities. Positive plant growth responses were absent when plants were treated with imidacloprid and insects were excluded. Results from a field study showed similar whitefly control and yield responses to imidacloprid and bifenthrin+ endosulfan applications. Hence, we conclude that growth and yield response to imidacloprid is associated with control of whiteflies and the subsequent prevention of damage, rather than a compensatory physiological promotion of plant growth processes.
    • Insectide Combinations for Whitefly Control in Broccoli

      Umeda, K.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Two pyrethroid insecticides, fenpropathrin (Danitol®) and bifenthrin (Capture®), were evaluated in several combinations with other insecticides for whitefly control in broccoli and demonstrated good efficacy to reduce eggs and immature stage insects. At one week after the second of three applications, Danitol® or Capture® plus methamidaphos (Monitor®), acephate (Orthene®), or endosulfan (Thiodan®) significantly reduced egg counts relative to the untreated check.
    • Cabbage Variety Trials 1994/1995

      Wilcox, Mark; Oebker, Norman F.; Yuma Valley Agricultural Center (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.
    • Mixed Lettuce and Romaine Variety Trials 1994/1995

      Wilcox, Mark; Oebker, Norman F.; Yuma Valley Agricultural Center (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
    • Identifying Short-Range Migration by the Sweet Potato Whitefly

      Byrne, David N.; Palumbo, John C.; Orum, T. V.; Rathman, Robin J.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Populations of the sweet potato whitefly, Bemisia tabaci, have been shown to consist of both migratory and trivial flying morphs. The behavior of these forms as part of the process of short-range migration needed to be examined under field conditions. Insects were marked in a field of cantaloupes using fluorescent dust. During the first growing season traps, used to collect living whiteflies, were placed along 16 equally spaced transects (22.5° apart) radiating out from the field to a distance of up to 0.6 miles. Wind out of the northeast consistently carried migrating whiteflies to traps placed along transects in the southwestern quadrant because cold air drainages dictate wind direction during early morning hours. For this reason, during the second season traps were laid out in a rectangular grid extending 3 miles to the southwest of the marked field. If dispersal was entirely passive or wind directed patterns could be described using a diffusion model. Statistical examination of the data, however, demonstrate that the distribution on all days was patchy. Traps in the immediate vicinity of the marked field caught more whiteflies than the daily median. Large numbers were also collected from around the periphery of the grid. Whiteflies were far less prevalent in the grid's center. As a result, the distribution of captured whiteflies can be described as bimodal. These patterns confirm behavior observed in the laboratory, i.e., a portion of the population are trivial fliers that do not engage in migration and are consequently captured in traps near the field and a portion initially ignore vegetative cues and fly for a period of time before landing in distant traps. This second population comprises the second peak in the model that appeared 1.6 miles from the marked field. On a localized level, 1.6 miles seems to be how far whiteflies move in a day. Earlier studies indicate that whiteflies only fly one day.
    • Soil-Applied Herbicides for Weed Control in Broccoli

      Umeda, K.; Gill, A.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Three commonly used herbicides for use in broccoli were effective when applied alone or in combinations as a preplant incorporated (PPI) or a preemergence (PE) application. DCPA (Dacthal®) at 10.0 lb product/A PE gave acceptable control of most weeds. Trifluralin (Treflan® SEC) at 1.0 pt/A and bensulide (Prefar® 4EC) PPI were also effective but mustard weeds were not adequately controlled. Combinations of the herbicides at lower rates did not provide any advantage in improving weed control efficacy.
    • 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.
    • 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.
    • New Insecticides for Potential Use for Whitefly Control in Cantaloupes

      Umeda, K.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Most experimental treatments effectively reduced Bemisia tabaci [sweetpotato whitefly (WF) also known as silverleaf WF, B. argentifolii] adults and eggs in cantaloupes relative to the untreated check at 6 days after treatment of each of five applications. Acephate (Orthene®), buprofezin (Applaud®), bifenthrin (Capture®), endosulfan, fenpropathrin (Danitol®), naled (Dibrom®), and pymetrozine(CGA -215944, Ciba) treatments had the fewest adults and eggs. Insect growth regulator (IGR) materials in combinations, pyriproxyfen (S-71639, Valent) and fenoxycarb (Ciba),were more effective in reducing WF relative to the untreated check than when applied alone. Registered products, Dibrom®, endosulfan, and methamidaphos (Monitor®) were effective in combinations or in alternating applications.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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)
    • Impact of Sweet Potato Whitefly Infestation on Yield and Quality of Cantaloupe

      Palumbo, J. C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      A range of population levels of sweet potato whitefly, Bemisia tabaci Gennadius was evaluated in three field experiments allowing measurement of the effect of whitefly numbers on melon quality and yield. An increase in total numbers of immature whitefly was associated with significant declines in harvested melon weight, a decline in number of boxes harvested, a decrease in fruit size, a decrease in percent sugars, and an increase in sooty mold. Regression analysis of individual whitefly life stages with yield parameters indicated that adult number was a more precise parameter and higher R2 values were obtained with increased range of whitefly population densities. Adults were sampled at the third leaf node in both locations. Nymph samples were taken at varying nodes from the base of the plant. Estimates of the mean adult whitefly density resulting in 5% and 15 % dollar yield loss were 3 and 10 adults per leaf Estimates of the mean total nymph density resulting in 5% and 15% dollar yield loss 0.5 and 2 (AZ) nymphs per cm² of leaf area, respectively.
    • 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.