• Evaluation of New Preemergence and Postemergence Herbicides for Onion Weed Control

      Umeda, K.; Lund, N.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      In the preemergence test, flumioxazin at 0.1 to 0.3 lb AI/A severely reduced the onion crop stand. Flumioxazin applied caused significant onion injury of 23 to 37% at 2 WAT for rates of 0.04 to 0.1 lb AI/A. Fluroxypyr and carfentrazone applied postemergence did not show any onion injury at 5 WAT. Fluroxypyr and carfentrazone did not offer acceptable control of annual yellow sweetclover at any rate. Carfentrazone at 0.063 lb AI/A demonstrated activity on lambsquarters and control nearly approached acceptable levels at 83% after 5 WAT. Fluroxypyr did not provide acceptable control of lambsquarters.
    • Field Evaluation of Romaine Lettuce Varieties Grown in Southwest Low Desert Soils

      Zerkoune, Mohammed A.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Romaine lettuce plays an important role in Yuma’s economy. An estimated 10,000 acres are cropped to large number of varieties each year with planting season that spreads from September to March. The demonstration site was selected to compare new and existing varieties of romaine lettuce on growers’ fields using standard farming practices. Selected growth parameters were evaluated throughout the growing season. Results indicate that varieties tested at Barkley Farms in Yuma are expected to do well if grown under similar growing conditions and planting time. Varieties tested during this planting slot did not experience any incidence of diseases. There was no significant head size and head weight difference among varieties evaluated. Number of heads per bed and number of heads left after harvest were significantly different among varieties tested.
    • Sustaining Arizona's Fragile Success in Whitefly Resistance Management

      Li, Andrew Y.-S.; Dennehy, Timothy J.; Li, Sarah X.-H.; Wigert, Monika E.; Zaborac, Marni; Nichols, R. L.; Byrne, David N.; Baciewicz, Patti; Cotton Incorporated, Cary, North Carolina (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Arizona cotton experienced a severe crisis in 1995 stemming from resistance of whiteflies to synergized pyrethroid insecticides. The insect growth regulators (IGRs), Knack® (pyriproxyfen) and Applaud® (buprofezin), served a pivotal role in resolving this problem. Similarly, Admire® (imidacloprid), the first neonicotinoid insecticide to obtain registration in Arizona, has been the foundation of whitefly control in vegetables and melons. In this paper we provide an update regarding the susceptibility to key insecticides of whiteflies from Arizona cotton, melons, and greenhouses. Overall, whitefly control in Arizona cotton remained excellent in the 2000 season and there were no reported field failures. However, there was a significant decrease in susceptibility to Applaud of whiteflies collected from cotton. One collection from Eloy, Arizona, in 2000 had susceptibility to Applaud that was reduced 129-fold relative to a reference strain. Whiteflies resistant to Knack, detected for the first time in Arizona in 1999, were again detected in 2000 but at lower frequencies than in 1999. Though whiteflies resistant to Admire/Provado® continued to be found at specific locations, overall susceptibility to Admire/Provado in 2000 remained high in whitefly collections from cotton. The new neonicotinoid insecticides, thiamethoxam and acetamiprid, were similar in toxicity to Arizona whiteflies in laboratory bioassays and we confirmed the significant but relatively low-order cross-resistance we previously reported between these neonicotinoids and Admire/Provado. Arizona whiteflies continued to be relatively susceptible to mixtures of Danitol® (fenpropathrin) and Orthene® (acephate). Factors that could undermine the current success of whitefly resistance management in Arizona are discussed. These include: 1) more severe resistance to IGRs in whiteflies from cotton, stemming from increased IGR use within and outside of cotton; 2) resistance of vegetable, melon and greenhouse whiteflies to the various formulations of imidacloprid (Admire, Provado, Merit®, Marathon®); 3) the imminent registration of new neonicotinoid active ingredients in cotton, greenhouses and other Arizona crops.
    • Residual Efficacy and Field Performance of Thiacloprid (Calypso) Against Whiteflies in Melons

      Palumbo, John C.; Reyes, F. J.; Mullis, C. H. Jr.; Amaya, A.; Ledesma, L.; Carey, L.; Byrne, David N.; Baciewicz, Patti; Department of Entomology, Yuma Valley Agricultural Center (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Studies were conducted to compare the residual field efficacy of Calypso, compared with soil applications of Admire and foliar sprays of Provado and Actara. The results demonstrate that several insecticide product uses are being developed that offer melon growers management alternatives for controlling whiteflies comparable to what they have experienced with Admire. Calypso showed excellent promise as a foliar, post-planting spray with good residual activity. Two spray applications provided good whitefly control and excellent crop and melon quality. Although we saw a measurable impact on some natural enemies, the compound is supposedly very safe to honeybees. Overall, when directed at low adult and immature densities, Calypso provided 14-21 days of residual control and was capable of preventing yield and quality losses in spring melons. These studies also emphasize, that like the IGRs, these foliar neonicotinoids should be used when whiteflies densities are low and beginning to build. This compound may be available as early as 2002.
    • Comparison of New Fungicides for Management of Downy Mildew of Broccoli in 2001

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Downy mildew of broccoli, cauliflower and cabbage is caused by the fungus Peronospora parasitica. Cool moist environmental conditions favor the development of downy mildew on these crops. Several potential new fungicides were evaluated for control of this disease on broccoli in 2001. The final severity of downy mildew in this trial was moderate. Significant reduction in disease severity compared to nontreated plants was achieved by application of available compounds such as Aliette, Bravo, Maneb, Serenade and Trilogy. The nonregistered chemistries Acrobat, Actigard, Curzate, Flint, BAS 500, DPX-KP481 and Quadris also were active against broccoli downy mildew. Actigard was the superior treatment in this trial, as plants treated with this compound were almost free of disease. The future registration and subsequent availability of one or more of these new chemistries for broccoli and related crops could enhance the overall level of disease control as well as help minimize the risk of development of resistance to fungicides used to manage downy mildew.
    • Reaction of Different Cultivars of Lettuce to Development of Powdery Mildew on Lettuce in 2001

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Seven different cultivars of lettuce were seeded and watered on Dec 1, 2000 at the Yuma Valley Agricultural Center. Cultivars were rated for severity of powdery mildew caused by Erysiphe cichoracearum at plant maturity (Mar 21). The highest levels of powdery mildew were found on the cultivars Winterhaven and Silverado, whereas lower disease severity was observed on Jackel, Cibola, RC-74 and Accolade. All tested cultivars would have required application of fungicides to reduce the amount of powdery mildew to acceptable levels. On the other hand, planting of lettuce cultivars with some disease tolerance may require less fungicide inputs to achieve acceptable disease control compared to planting susceptible cultivars.
    • Preemergence Herbicides for Weed Control in Melons

      Umeda, K.; Lund, N.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      All herbicide treatments, Prefar, Frontier, Dual Magnum, Valor, and Prefar combined with Dual Magnum or Frontier caused less than 10% injury on cantaloupes. Frontier at 0.75 lb AI/A, Dual Magnum at 1.0 lb AI/A, Valor at 0.03 and 0.05 lb AI/A controlled weeds similar to Prefar. Prefar at 4.0 lb AI/A combined with Frontier controlled tumble pigweed (94%), narrowleaf lambsquarters (95%), Wright’s groundcherry (97%), and horse purslane (94%). None of the preemergence herbicide treatments controlled purple nutsedge.
    • Field Evaluation of Broccoli Varieties Grown in Southwest Low Desert Soils

      Zerkoune, Mohammed A.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Based on the acreage, broccoli is the third largest vegetable crop in Yuma County, after head lettuce and romaine. It generates over 36 million dollars to Yuma's economy. Efforts are continuously made by growers, seed industry and the University of Arizona outreach program to produce better crops that respond to consumer’s choice. Selection of newly adapted varieties is made based on agronomic performance as well as commercial value. Stand uniformity disease resistance, vigor, head shape and head size are among characteristics that are evaluated. The objective of this demonstration trial is to evaluate the performance of newly developed varieties grown under standard cultural practices and to provide unbiased observations to growers and the seed industry. Fourteen varieties were tested on growers' fields in Yuma County. No incidence of disease was observed among varieties tested and the overall evaluation rating was greater than 4 indicating that most of varieties tested will grow well under similar growing conditions and planting date. Significant head diameter and plant height was observed among varieties evaluated.
    • Effect of Prowl and Prefar Herbicides on Onions

      Umeda, K.; Lund, N.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Significant onion height reduction was observed when Prowl (pendimethalin) and Prefar (bensulide) herbicide combinations were applied preemergence (PREE). The onions resumed growth but the height was still slightly reduced later in the growing season compared to the handweeded check and the standard herbicide treatment, Dacthal (DCPA). The onion crop stand emerged initially but later in the season, a significant crop stand reduction was observed for the higher rate of Prowl at 0.5 lb AI/A plus Prefar. A lower rate of Prowl at 0.25 lb AI/A plus Prefar also caused a reduction of the onion stand compared to the handweeded check or Dacthal.
    • Interactions Between Insecticides, Spray pH, & Adjuvants

      Palumbo, John C.; Reyes, F. J.; Carey, L.; Amaya, A.; Ledesma, L.; Byrne, David N.; Baciewicz, Patti; Department of Entomology, Yuma Valley Agricultural Center (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Studies were conducted in the laboratory to investigate how the addition of a insecticides to two sources of Colorado River water would effect the pH of spray mixtures. In addition, we were curious what the effects of various labeled concentrations of buffers, acidifiers, spreader/stickers, and foliar nutrient sprays would have on the pH of spray water. Results showed that in most cases, spray concentration remained alkaline following addition of insecticides and adjuvants, with variations occurring primarily for the OPs. Buffering agents dramatically lowed pH at concentration greater than 0.25% v/v. Studies were also designed to evaluate the knockdown and residual mortality of Success against worms when applied in an acidic spray solution. Bioassays of larval mortality on field-treated foliage showed that knockdown mortality was not affected, but residual efficacy was significantly reduced when Success was applied using acidic (pH 4.2) spray solutions.
    • Influence of Admire and Platinum on the Population Growth of the Lettuce Aphid Under Field Conditions

      Palumbo, John C.; Byrne, David N.; Baciewicz, Patti; Department of Entomology (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Studies to examine lettuce aphid population growth on Admire and Platinum treated plants were conducted on head lettuce at the Yuma Agricultural Center. By artificially infesting plants on several lettuce plantings during the spring, the influence of insecticide residual and temperature were measured. Results of five field trials suggest that both Admire and Platinum can have a significant influence on lettuce aphid population growth. Depending on timing of infestation and insecticide residual, significant suppression of population growth can result from the application of these compounds. Infestations initiated at 28 d following Admire application initially resulted in minimal population growth, but later allowed aphids to reproduce at high numbers. In both cases, Admire provided about 90% control of the lettuce aphid population. However, aphid infestations occurring at later periods of plant residual almost always resulted in higher population development. In addition, these studies also support conclusions drawn form last season that suggested lettuce aphid population growth is greatest when ambient temperatures average between 65-70 ºF.
    • Neonicotinoids and Azadirachtin in Lettuce: Comparison of Application Methods for Control of Lettuce Aphids

      Palumbo, John C.; Reyes, F. J.; Mullis, C. H. Jr.; Amaya, A.; Ledesma, L.; Carey, L.; Byrne, David N.; Baciewicz, Patti; Department of Entomology, Yuma Valley Agricultural Center (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Several small-plot field studies were conducted at the University of Arizona, Yuma Agricultural Center in the spring 2001 growing season to evaluate various neonicotinoids and azadirachtin products against lettuce aphid, Nasonovia ribisnigri, in lettuce. Further, these products were compared as soil-applied treatments, foliar sprays and application through sub-surface irrigation. The results of these trials provide useful information for understanding how to effectively use the new chemistries available for aphid management in lettuce. First, Platinum performed best as a post-planting application through a side-dress application or through the drip. The foliar neonicotinoids, Assail and Actara were active against lettuce aphids, but were most effective when populations densities were lower. Comparatively, the conventional chemistries (MSR, Orthene/Provado, Provado/Endosulfan) provided consistent control when used aggressively. The azadirachtin products were significantly less effective against LA in head lettuce due largely to their inability to contact the insects, but on formulation (AzaDirect) showed better efficacy when applied through drip irrigation or sprayed repeatedly in romaine lettuce.
    • Timing of Glyphosate Application for Weed Control in Glyphosate Tolerant Lettuce

      Umeda, K.; Hicks, T. V.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Studies were conducted to determine the optimum time to apply glyphosate to glyphosate-tolerant Lactuca sativa cv. Raider (head lettuce). The study was initiated near Yuma, Arizona in September 2000. Single applications of glyphosate at 1.0 lb AI/A were made to head lettuce at development stages of 2, 4, 6 and 8 leaves. Glyphosate treatments did not injure lettuce. A single application at the 2 or 4 leaf stage was optimal for near complete control of Portulaca oleracea (common purslane), Chenopodium murale (nettleleaf goosefoot), Malva parviflora (cheeseweed), and Leptochloa spp. (sprangletop). Later applications at the 6 or 8 leaf stages allowed weeds, especially, common purslane to compete with the crop. Treatments applied at the 2 or 4 leaf stages required the least amount of time to hand weed and resulted in highest fresh weight yields.
    • New Postemergence Herbicides Evaluation in Cantaloupes

      Umeda, K.; Lund, N.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Halosulfuron applied POST with an adjuvant and ammonium sulfate was effective against lambsquarters and nutsedge. Rimsulfuron, flumetsulam, and thifensulfuron were effective against the pigweeds and purslane with minimal activity against lambsquarters. Halosulfuron and rimsulfuron were safe on melons and flumetsulam and thifensulfuron were marginally safe on cantaloupes. The combinations of these products may offer broader spectrum weed control.
    • Examination of New Chemistries to Control Powdery Mildew of Cantaloupe in 2000

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Powdery mildew can occur on melons annually in Arizona. Sphaerotheca fuliginea is the plant pathogenic fungus that causes powdery mildew of cucurbits, such as cantaloupe, honeydew, watermelon, cucumber and squash. When environmental conditions are favorable, disease incidence and severity can reach economically significant levels. Development of powdery mildew on melons is favored by moderate temperatures and relative humidity, succulent plant growth and reduced light intensity brought about by a dense plant canopy. Potential new fungicides were evaluated and compared to existing chemicals for control of powdery mildew of cantaloupe in a field trial conducted during the spring of 2000 at the Yuma Agricultural Center A moderately high level of disease had developed by crop maturity (June 22) on nontreated plants. All treatments significantly reduced the level of powdery mildew on both sides of leaves, compared to nontreated plants. The best treatments among those tested with respect to disease control on the underside of leaves, where disease is more difficult to control than on the tops of leaves, included Actigard, Armicarb+Quadris, BAS 500, Benlate+Microthiol, Flint, Flint+Trilogy, Microthiol, Quadris+Actigard, Quadris+Benlate, Quinoxyfen, Nova, Nova+KHHUBF, Topsin, Topsin+Trilogy, Benlate, Benlate+Trilogy, Folicur, Quadris and Topsin+Microthiol. The potential availability of new chemistries for management of powdery mildew of cantaloupe and other cucurbits could help improve overall control of powdery mildew as well as facilitate the development of fungicide resistance management strategies, which strive to minimize the risk of resistance development by the pathogen to these compounds.
    • Interaction of Pepper Experimental Lines with Phytophthora Crown and Root Rot in 2000

      Matheron, Michael E.; Crosby, Kevin M.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      This study was conducted in the greenhouse at the Yuma Agricultural Center. Thirty-nine experimental lines of pepper from the Texas A&M pepper breeding collection were seeded and grown in the greenhouse in 8 fl. oz. plastic pots. When plants were 2 months old (Aug 8), the potting mix in each pot was infested with Phytophthora capsici. Plants were placed in 2-in. deep containers filled with water for 48 hr every 2 weeks, which maintained the potting mix in a saturated condition and encouraged disease development. The mean temperature of the potting mix from the time it was infested with Phytophthora capsici to the termination date of the study was 81 °F. Disease progress and the relative susceptibility of each test plant to Phytophthora crown and root rot was assessed by recording the date when each plant displayed necrosis around the lower stem and was permanently wilted. The environmental conditions during this study were very favorable for disease development. The mean duration of plant survival for pepper selections ranged from 9 to 51 days. If no plants had died due to Phytophthora crown and root rot, the duration of plant survival would have been 74 days. Most plant selections were readily attacked and killed by Phytophthora capsici. The experimental lines with the highest survival rating may be somewhat tolerant to disease; however, additional testing in further greenhouse and field trials is required to substantiate these preliminary results.
    • Grass Weed Control in Melons

      Umeda, K.; Lund, N.; MacNeil, D.; Robertz, D.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Efficacy of the grass herbicides showed that Select (clethodim) and BAS-620 (BASF Corporation) at rates as low as 0.1 lb AI/A were nearly comparable in controlling 2 leaf stage of growth watergrass or when applied a week later on 3-4 inch tall watergrass. Fusilade DX (fluazifop-p-butyl) was intermediate in controlling grasses and 0.188 lb AI/A was necessary to give equivalent control of larger grasses as compared to the 0.1 lb AI/A rate that gave acceptable control of smaller grasses. Poast (sethoxydim) at 0.188 lb AI/A gave acceptable control of small grasses but lower rates or later timed applications were not as efficacious.
    • Evaluation of Fungicide Rotations for Control of Powdery Mildew of Cantaloupe

      Olsen, M. W.; Rasmussen, S.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      A fungicide trial was established at The University of Arizona Marana Agricultural Center in April 2000 to evaluate rotation and timing of application for several fungicides used for control of powdery mildew on cantaloupe. Treatments included seven registered fungicides: azoxystrobin, micronized sulfur, neem extract, potassium bicarbonate, benomyl, thiophanate methyl and trifloxystrobin. Different rotations and timing of application of these fungicides were applied either before or immediately after initial signs of powdery mildew infection and up to three times thereafter depending on rotation scheme. By the second application, disease severity was mild but increased rapidly, and it was severe by the time of the last application. Powdery mildew was controlled to some degree on the upper leaf surface by all treatments. However, efficacy was more variable on the lower leaf surface and was reduced when applications were made only at dates 1 and 2. Results show the increased efficacy of fungicides with systemic or trans-laminar activity and the possibilities of rotations with contact fungicides for resistance management.
    • Herbicide Screen for Melons

      Umeda, K.; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      In the preemergence test, azafenidin, flufenacet, thiazopyr, isoxaben, dithiopyr, and thifensulfuron exhibited safety on cantaloupes and watermelon at rates higher than rates required for effective weed control. In the postemergence test, the margin of selectivity for melon safety and weed control was narrow for MKH-6561, flufenacet, and thifensulfuron. MKH-6561 and CGA-362622 applied preemergence did not offer any acceptable crop safety relative to the weed control that was observed. Azafenidin, thiazopyr, isoxaben, and pyrithiobac did not demonstrate adequate melon safety compared to providing good weed control.
    • Fungicide Performance for Control of Powdery Mildew on Lettuce in 2001

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2001-08)
      Powdery mildew on lettuce is caused by the fungus Erysiphe cichoracearum. This disease is favored by moderate to warm temperatures and dry weather conditions. Several potential new fungicides were evaluated for control of powdery mildew on lettuce in 2001. Powdery mildew appeared in our plots by Jan 16 and reached high levels by plant maturity on Mar 13. Nontreated lettuce plants were heavily infected with powdery mildew at plant maturity, whereas the level of disease was low to virtually nonexistent in plots treated with BAS 500, Flint, Rally, Rally alternated with Microthiol, Microthiol and Quinoxyfen. The future availability of one or more of these chemistries under development could help in efforts to control powdery mildew of lettuce and to establish and maintain a fungicide resistance management program for plant disease control products of importance for this crop.