• Effect of a Plant Growth Regulator on Green Beans Grown for Processing

      Rethwisch, Michael D.; Beckstead, Dick; Parker, Larry; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Three rates of the plant growth regulator Foliar Triggrr were applied to green beans grown for processing at 5% bloom. The 6 oz rate increased yields of size 1 and 2 beans compared to all other treatments and the untreated check and had the fewest size 3 beans (which would be culls). The 11 oz rate was similar to the untreated check while the 16 oz rate decreased yields. Total bean numbers per plant were similar. Although treatment differences in this experiment were not statistically significant, a yield increase of 10.2% for the 6 oz rate compared with the untreated check may well result in increased economic returns.
    • Crisphead Lettuce Variety Trials 1995/96

      Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
    • Management of Downy Mildew on Broccoli: Efficacy of Fungicides in 1996 Field Trial

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      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 management in a field trial conducted in 1996. Disease pressure was moderate and all tested fungicides except Ridomil MZ 72 and one Ciba G + Mancozeb treatment significantly reduced the number of downy mildew lesions on leaves compared to plants not treated with a fungicide. The level of disease reduction provided by all chemical treatments was equivalent to that given by Aliette and Bravo, two fungicides currently available for control of downy mildew on broccoli.
    • Management of Downy and Powdery Mildew on Lettuce: Efficacy of Fungicides in 1996 Field Trial

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Downy and powdery mildew are caused by the plant pathogenic fungi Bremia lactucae and Erysiphe cichoracearum, respectively. Cool and moist environmental conditions favor development ofdowny mildew, while warmer and dry weather is conducive for development of powdery mildew. Potential new fungicides were evaluated for management of these diseases in 1996. Both downy and powdery mildew developed in the test plots. All tested materials significantly reduced the severity of downy mildew compared to plants not treated with a fungicide. Compared to nontreated control plants as well as some tested materials and rates, significant reduction of powdery mildew was achieved with Azoxystrobin 80WDG + Latron B-1956, BAS 490 02F, Ciba G /MZ + Mancozeb 75DF, Dithane 75DF + Latron CS-7, Propamocarb 6EC (high rate), R11-7281 2F + Larron CS-7, and Microthiol 80WDG.
    • Management of Sclerotinia Leaf Drop on Lettuce: Efficacy of Fungicides in 1996 Field Trial

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      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 a field trial for management of this disease in 1996. For plots containing Sclerotinia minor, all compounds and rates tested significantly reduced the number of diseased heads compared to plots not treated with a fungicide. All treatments except Ronilan at the 0.5 lb. a. i./A rate yielded a significantly higher number of marketable heads compared to nontreated plots infested with S. minor. For plots containing S. sclerotiorum, all materials except the Ciba compound at the low and high rates decreased the number of diseased heads and increased the number of marketable heads compared to nontreated plots.
    • Temporal Activity of New Insecticde Chemistries Against Beet Armyworm in Lettuce

      Palumbo, John C.; Kerns, David L.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Three new insecticide chemistries (Alert, Spinosad and Confirm) were evaluated and compared with standard chemistries for temporal mortality of beet armyworm in lettuce. Field assessment and lab bioassay were conducted at the thinning, heading, and harvest stage of lettuce. Results from both the field and laboratory indicated similar trends for the temporal activity of the products. Alert appears to be have the most rapid "knockdown activity" with 100% mortality consistently occurring by 2 DAT. Spiniest, a naturalyte insecticide, has activity similar to Larvin. Both require 2-3 days to achieve complete larval mortality. Confirm, a new IGR selective for lepidoptera, requires significantly more time to achieve complete mortality (4-5 DAT). It can be compared with Bt (Xentari) activity in that it has initially slow activity. However, unlike Bt, it can effectively cause complete beet armyworm mortality. The results of this study are consistent with similar studies we conducted in 1994 and 1995 and provide basic guidelines concerning the activity and assessment of the performance of these materials in the field. However, PCAs and growers will ultimately be able to develop specific use patterns for these materials within their individual lettuce pest management programs.
    • Insecticides for Whitefly Control in Cantaloupes

      Umeda, K.; Fredman, C.; Fredman, R.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Several experimental insecticide treatment combinations were evaluated and demonstrated very good efficacy against Bemisia argentifolii [silverleaf whitefly (WF) also known as sweetpotato WF, B. tabaci]. Adults and immatures were most effectively reduced compared to the untreated check by pyriproxyfen (S-71639, Valent) treatments and fenpropathrin (Danitol®) plus acephate (Orthene®). CGA-215944 (Ciba) plus fenoxycarb (Ciba) treatments compared favorably with many of the pyrethroid combination treatments. Registered products esfenvalerate (Asana®), endosulfan (Thiodan®), cypermethrin (Ammo®), naled (Dibrom®), and oxydemeton-methyl (Metasystox-R®) complemented many of the combination treatments to reduce WF relative to the untreated check
    • Timing and Frequency of Provado® Applications for Management of Aphid Populations in Head Lettuce

      Palumbo, John; Mullis, Clayton Jr.; Reyes, Francisco; Amaya, Andreas; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Provado insecticide (imidacloprid) was compared to Admire and other standard insecticides for management of aphids in head lettuce in Yuma 1995 and 1996. Foliar applications of Provado appear to provide an alternative method of controlling aphids on lettuce comparable to prophylactic applications of Admire. The prevention of aphid colonization in lettuce heads with Provado may depend greatly on the timing and frequency of applications before harvest occurs. These studies and other studies on spinach suggest that more than one application of Provado will be necessary to adequately suppress aphid contamination in heads. The label suggests that applications be timed 5-7 apart. Our data tends to support this recommendation. Furthermore, timing applications should be based on days to harvest, level of aphid colonization and duration of aphid migration.
    • Mulching Cantaloupes with Plastic at Yuma 1996

      Oebker, N. F.; Sanchez, C. A.; Wilcox, Mark; Palumbo, J. C.; Matheron, M. E.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Six mulches were compared to no mulch on cantaloupes at Yuma in the Spring of 1996. The IRT film and black mulches caused "Mission" cantaloupes to produce significantly higher early yields than white mulch or no mulch. Silver mulch gave good early and total yields. All mulches seemed to favor total production but in this test differences for total yields between mulched and non-mulched plots were not significant.
    • Residual Activity of New Insecticide Chemistries Against Beet Armyworm in Lettuce

      Kerns, David L.; Palumbo, John C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Three new insecticide chemistries (Alert, Success and Confirm) were evaluated and compared with standard chemistries for residual activity to beet armyworm in lettuce. Lettuce was treated in the field with the insecticides and left for 0, 3, 5 and 7 days. Leaves from treated plants were then brought into the laboratory where second instar beet armvworms were reared on them. Mortality was estimated 5 days after the worms were placed on the leaves. Bioassay were conducted at the thinning, heading, and harvest stages of lettuce. Under high temperature and light intensity, only Alert and Confirm provided the best residual control of beet armyworm, exhibiting good activity for about 3 days after application. Success had better residual activity than Lannate, and both were better than Xentari. Under cool temperatures and low light intensity conditions, Alert, Confirm and Larvin exhibited good activity for at least 5 days following an application, (7 days or greater for Alert and Confirm). Lannate and Xentari both had greater residual activity late in the season, but were not as effective as Alert, Confirm or Larvin. Late season activity of Success did not appear to differ much from early season observations, and did not appear to provide more than 3 days residual activity.
    • Postemergence Herbicide Weed Control in Onions

      Umeda, Kai; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Onions treated at the 2-leaf stage of growth with the 3rd leaf just beginning to emerge with postemergence herbicides bromoxynil (Buctril®) and oxyfluorfen (Goal®) exhibited slight injury at 11 days after treatment (DAT) but had recovered to show no injury at 1 month after treatment (MAT). Annual yellow sweetclover (Melilotus officinalis) was the predominat weed in the test site and early ratings showed that Goal at 0.25 lb a.i. /A and Goal plus Buctril gave marginally acceptable control at 80 %. Buctril alone did not control clover. At 1 MAT, the clovers had recovered from the initial injury and the level of control had declined to become unacceptable.
    • Cantaloupe Variety Trials 1996

      Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
    • Management of Powdery Mildew on Cantaloupe: Efficacy of Fungicides in 1995 Field Trial

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Powdery mildew of cantaloupe and other melons 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 management in a field trial conducted in the spring of 1995. In this study, BAS-490 and Reach provided the highest level of efficacy among the materials and rates tested. Generally, lower levels of disease led to increased yield of marketable fruit.
    • Postemergence Herbicide Weed Control in Broccoli

      Umeda, Kai; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      An exploratory field study provided results of postemergence herbicide weed control efficacy and broccoli tolerance. Pyridate (Tough®), clopyralid (Stinger®), and oxyfluorfen (Goal®) did not cause any crop stand reduction compared to bentazon (Basagran®) that completely reduced the broccoli stand. Tough and Goal at the lower rates tested caused marginally acceptable broccoli injury. Goal effectively controlled pigweed species (Amaranthus sp.), groundcherry (Physalis wrightii), and purslane (Portulacç oleracea). Tough gave good control of pigweed and purslane but not groundcherry. Stinger was safe on broccoli and marginally controlled groundcherry. In a second field study, Tough and Goal were evaluated for cheeseweed control. Goal marginally controlled cheeseweed at all rates tested and caused marginally acceptable injury at the two lowest rates. Tough was relatively safe at the lower rates but did not adequately control the cheeseweed.
    • Broccoli Preemergence Herbicide Weed Control Studies

      Umeda, Kai; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Exploratory field studies conducted in broccoli showed that clomazone (Command®) and isoxaben (Gallery®) were extremely phytotoxic to broccoli when applied preemergence (PREE) on the soil surface after planting. Both offered good weed control of the weeds present. Napropamide (Devrinol®) caused moderate crop injury and marginally acceptable weed control.
    • Evaluation of Insecticides for Aphid Control in Cabbage

      Umeda, Kai; Fredman, Chris; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      Experimental insecticides CGA-215944 (Ciba), pyriproxyfen (S-71639, Valent), and RH-7988 (Rohm and Haas) demonstrated very good efficacy in reducing the aphid population in cabbage. Fipronil (Rhone-Poulenc) was not as effective in controlling the aphids relative to the other treatments. Acephate (Orthene®), chlorpyrifos (Lorsban™), and naled (Dibrom®) were highly effective relative to the untreated check.
    • Sweet Corn Tolerance and Herbicide Weed Control

      Umeda, Kai; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      No observable injury was evident by any herbicide treatment on any of the twelve sweet corn varieties during the season. Overall, pendimethalin (Prowl®) treatments applied preemergence (PREE) provided very good control ( >87 %) of all weeds rated. Metolachlor (Dual®), EPTC plus safener (Eradicane®), dimethanamid (Frontier®), and cyanazine ( Bladex®) treatments gave good control ( >80 %) of pigweeds ( Amaranthus sp.) and purslane (Portulaca oleraceq) with annual yellow sweetclover (Melilotus ocf`icinalis) not adequately controlled. All treatments except Bladex alone gave good control of volunteer sudangrass.
    • Optimal Soil Placement and Application Method of Admire® for Sweetpotato Whitefly Control in Head Lettuce

      Palumbo, John; Kerns, David; Sanchez, Charles; Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      The effects of Admire formulation and soil placement on colonization by sweetpotato whitefly, Bemisia tabaci (Gennadius), at three plant growth stages of lettuce, Lactuca sativa L., were evaluated in experimental and commercial lettuce plots in 1993-1994. We also evaluated the effects of Admire treatments on yield response and incidence of chlorosis associated with whitefly control. Admire placement had a significant affect on whitefly colonization in lettuce throughout the experimental period. Whitefly densities on lettuce varied at each plant stage relative to depth of placement within the lettuce seed bed. Applications made to the soil surface and at 1.5 inch sub-seed furrow followed by irrigation, provided the most consistent control of whitefly nymphs in both small plot and on -farm lettuce plots. These Admire soil treatments also prevented reductions in head size and incidence of leaf chlorosis associated with whitefly colonization in lettuce. Our data suggest that incorporation of Admire into the upper 1.5 - 2 inches of soil below the seed furrow is optimal for absorption and translocation by lettuce roots. Admire soil treatments may provide a more environmentally suitable and effective alternative to control of whiteflies in lettuce than is currently possible with foliar insecticide reatments.
    • Whitefly Control in Arizona Vegetables: Development of a Resistance Management Program for Imidacloprid (Admire®)

      Williams, Livy III; Dennehy, Timothy J.; Palumbo, John C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)
      In 1995 we initiated a resistance management program aimed at sustaining the efficacy of Admire®. This paper delineates the groundwork for the program, and describes methodological and conceptual advances toward our goal. Bioassay methods developed for adult whitefly consisted of a 1 day hydroponic uptake procedure using cotton seedlings. A reliable mortality criterion was also established. Results from a statewide survey suggested slight geographic variation in whitefly susceptibility to Admire®. Future studies will 1) continue to monitor susceptibility throughout Arizona, 2) evaluate the risk of resistance to whitefly populations in commercial greenhouses, and relate this to field populations, and 3) characterize the development of resistance in relation to cropping systems and spatial dynamics of whitefly. The overall objective of these investigations is to determine if a sustainable use strategy can be identified for Admire®.
    • Cauliflower Variety Trials 1995/96

      Wilcox, Mark; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1996-08)