• Insect Crop Losses and Insecticide Usage for Cantaloupes and Watermelons in Central Arizona: 2004 – 2006

      Palumbo, John; Fournier, Al; Ellsworth, Peter; Nolte, Kurt; Clay, Pat; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006-09)
      Impact assessment is central to the evolution and evaluation of our IPM programs. Quantifiable metrics on insecticide use patterns, costs, targets, and frequency, crop losses due to all stressors of yield and quality, and other real world economic data (e.g., crop value) are our most objective tools for assessing change in our systems. We recently initiated a project to measure the impact of insect losses and insecticide uses in cantaloupes and watermelons grown in Yuma, AZ and the Bard-Winterhaven area of Imperial County, CA. The data generated in this report is useful for responding to pesticide information requests generated by EPA, and can provide a basis for regulatory processes such as Section 18 or 24c requests, as well as for evaluating the impact of our extension programs on risk reduction to growers. This information also confirms the value of PCAs to the melon industry by showing the importance of cost-effective management of insect pests in desert production.
    • Crop Phenology for Irrigated Chiles (Capsicum annuum L.) in Arizona and New Mexico

      Soto-Ortiz, Roberto; Silvertooth, Jeffrey C.; Galadima, Abraham; Byrne, David N.; Baciewicz, Patti; Department of Soil, Water and Environmental Science, University of Arizona (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006-09)
      To determine growth and development patterns of irrigated green chile plants as a function of heat units accumulated after planting (HUAP), as well as to develop a general irrigated chile plant development model as a function of HUAP. Field experiments were conducted in 2004 and 20055 at Sunsites in Cochise County, AZ (about 4,000 ft. elevation) and at the Massey Farm in the Animas Valley, NM (about 4,392 ft. elevation). Basic plant growth and development measurements were collected routinely and important phenological stages that corresponded to first bloom, early bloom, peak bloom, physiological maturity, and red harvest were identified and recorded. Results indicate that among all sites, all varieties have performed similarly in relation to HU accumulation patterns and preliminary plant phenology models are under development in this program. The primary difference between sites was that at Sunsites varieties tend to reach a 50/50 (green: red chile) ratio at 2900 HUAP and for Animas valley; this same ratio was reached at 3200 HUAP. Also, a general irrigated green chile plant development model as a function of HUAP for all sites and varieties was obtained. The purpose of this phenological baseline or model is to assist growers in predicting and identifying critical stages of growth for crop management purposes. First bloom occurred at 1369 ± 72 HUAP, early bloom at 1667 ± 79 HUAP, peak bloom at 1998 ± 84 HUAP; physiological maturity at 2285 ± 159 HUAP, and red chile harvest was identified to occur at 3295 ± 216 HUAP.
    • Comparison of Products to Manage Sclerotinia Drop of Lettuce in 2006

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006-09)
      Sclerotinia drop on lettuce is caused by two soil-borne fungi, Sclerotinia minor and S. sclerotiorum. Moist soil and moderate temperatures favor this disease. Some registered products as well as new chemistries in development were compared for their ability to suppress Sclerotinia drop on lettuce during the winter vegetable growing season in 2005-2006. Sclerotia of each pathogen were incorporated into plots after lettuce thinning and just before the first application of test compounds. In plots infested with S. minor, a significant reduction in disease compared to untreated plots was achieved with Omega, Rovral, Endorse, Endura, and Switch. For plots containing S. sclerotiorum, disease was significantly reduced by Contans, Rovral, Omega and Endura. For a valid comparison of products for control of Sclerotinia drop of lettuce, it is important to compare the results obtained from more than one field study. The reader is urged to review previous studies in addition to this report to get an accurate picture of the relative efficacy of tested compounds for control of Sclerotinia drop. Fungicides are not the only tools available to growers to manage Sclerotinia drop. Cultural methods, such as soil solarization or soil flooding in the summer, as well as crop rotation, can greatly reduce the number of viable sclerotia in an infested field. Use of these cultural methods alone or in combination with fungicide treatments can result in dramatic reductions in the incidence of Sclerotinia drop of lettuce.
    • Evaluation of Fungicides as Potential Management Tools for Phytophthora Crown Rot on Pepper Plants

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006-09)
      Phytophthora blight of peppers (Capsicum annuum) is caused by the oomycete pathogen Phytophthora capsici. In Arizona, the root and crown rot phase of the disease initially can appear on plants early in the growing season in areas of the field where soil remains saturated with water after an irrigation or rainfall event. Disease severity can increase dramatically due to summer rains during July and August in the southeastern Arizona production area. The efficacy of the systemic fungicide mefenoxam (Ridomil Gold)) for control of Phytophthora blight on pepper has been documented; however, in many pepper production regions, populations of the pathogen insensitive to this fungicide have developed. Other chemistries, including dimethomorph (Acrobat) as well as some new fungicides in development, have activity on some species of Phytophthora and associated diseases on crops other than pepper. The objective of the following study was to evaluate additional chemistries for efficacy in suppressing development of root and crown rot on pepper plants grown in soil naturally infested with Phytophthora capsici. In the first trial, nontreated pepper plants were all dead after an average elapsed time of 5 days in soil infested with P. capsici. In the same trial, no plants died after 66 days when the soil was treated with Ranman (cyazofamid), V-10161 (fluopicolide), and Reason (fenamidone) + Previcur Flex (propamocarb). Additionally, only one out of five pepper plants died when treated with Omega (fluazinam), NOA-446510 (mandipropamid) and AgriFos (mono- and di-potassium salts of phosphorous acid). For all of these treatments, the duration of plant survival and fresh weight of plant shoots and roots did not differ significantly from plants grown in sterilized soil. Similar results were obtained in the second trial. The results from these trials suggest that several fungicides currently not registered for use on peppers may be effective components of a management program for Phytophthora root and crown rot. The data is promising; however, additional studies in field soil naturally infested with P. capsici are needed to confirm the preliminary findings of these initial experiments.
    • Cantaloupe Response to CN9™ Fertilizer

      Soto-Ortiz, Roberto; Silvertooth, Jeffrey C.; Galadima, Abraham; Byrne, David N.; Baciewicz, Patti; Department of Soil, Water and Environmental Science, University of Arizona (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006-09)
      Field experiments were conducted at four sites in 2005 in the Yuma Valley, AZ (approximately 150 ft. elevation) to evaluate the performance of CN9 fertilizer [a N-calcium (Ca) based fertilizer (9-0-0-11)] in comparison to a conventional N fertilizer source with irrigated melons/cantaloupes (Cucumis melo L.). Each field was divided into two equal (approximately 40 acres) sections. One section received the grower’s N fertilizer source (Conventional) while the other section received the CN9 fertilizer. Basic plant growth and development measurements, aboveground biomass, total and marketable yield, Sugar fruit content as well as total nutrient analysis were among the main variables analyzed. In general, all phenology variables responded similarly between conventional and CN9 treatments. Fresh weight yields ranging from 4,000 to 10,000 kg/ha were observed between conventional and CN9 treatments. Statistical analyses show that total yield between conventional and CN9 was statistically the same; with the exception of the Perriconi site. Similar results were observed for marketable yield. Brix values ranged from 10 to 14 percent, statistical differences for Brix values between the conventional and CN9 treatments were found on the Perriconi and Mason 80 sites where the conventional treatment had higher sugar content in the fruit. Overall, there were no differences in nutrient uptake and allocation patterns due to the addition of CN9 among experimental sites or sampling dates. Regarding the allocation of nutrients in the rind and flesh of melons, the same patterns between treatments at all sites were observed.
    • Action Thresholds for Aphid Management with Reduced-Risk and Conventional Insecticides in Desert Head Lettuce

      Palumbo, John; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006-09)
      Action thresholds, based on the percentage of plants infested, for the aphid pest complex found in head lettuce were evaluated in October, November and December plantings in 2005 and 2006 at the Yuma Agricultural Center. Action thresholds were also evaluated for their compatibility with newly developed reduced-risk and conventional insecticides. Although all five common aphid species were present in both years of the study, foxglove aphids provided most of the pest pressure. Compared with the SAC threshold treatment (sprayed-at colonization; essentially sprayed weekly until new aphid colonies were not found), action thresholds of 10% and 30% plants infested with 5 or more aphids resulted in fewer insecticide applications, while maintaining varying levels of head contamination at harvest. Despite variable pest pressure between years and planting dates, the threshold based on 10% infested plants performed as well as the SAC but with half as many sprays and no significant head contamination. However, significant head contamination was experienced when the 10% action threshold was used exclusively with reduced-risk insecticides.
    • Evaluation of a Biologically Intensive Integrated Pest Management System for Sclerotinia Drop on Lettuce: 2006 Study

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006-09)
      Sclerotinia drop of lettuce, caused by the pathogenic fungi Sclerotinia minor and S. sclerotiorum, is a serious disease in most regions were this crop is grown. Conventional fungicides, such as Rovral (iprodione) and Endura (boscalid), are usually applied after lettuce is thinned and once more 2 to 3 weeks later. Two biological products, Contans (Coniothyrium minitans) and Serenade (Bacillus subtilis), are also available. In earlier field trials conducted from 2001 to 2004 in the presence of S. minor, the mean reduction in disease by Contans, Serenade and Endura was 36, 21 and 51%, respectively. The main objective of the current study was to determine the efficacy of the biological products Contans and Serenade, applied alone or in combination with each other or the conventional fungicide Endura, within a biologically intensive integrated pest management system for Sclerotinia drop on lettuce caused by S. minor. The study was conducted at the The University of Arizona, Yuma Valley Agricultural Center. Sclerotia of Sclerotinia minor were produced in the laboratory. Lettuce ‘Winterhaven’ was seeded and sclerotia were applied to the plots on Nov 14, 2005 and the final disease assessment at plant maturity was made Mar 13, 2006. There was a high degree of variability among the replicate plots for each treatment in this trial, as well as an overall low disease incidence, which made statistical comparisons of data difficult. The only treatment in this trial that significantly lowered disease incidence compared to nontreated plots was an initial application of Contans at seeding followed by Endura at thinning. This study was established in a field containing well-draining loam soil, which combined with the lack of any rainfall and the use of furrow irrigations in January and February, which kept the tops of beds dry, likely contributed to the excessive variability and low incidence of disease.
    • Assessment of Fungicide Performance for Management of Powdery Mildew on Cantaloupe in 2006

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006-09)
      Powdery mildew occurs annually on melons in Arizona. Podosphaera xanthii (Sphaerotheca fuliginea) is the plant pathogenic fungus that causes powdery mildew on cucurbits, such as cantaloupe, honeydew, watermelon, cucumber and squash. 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. Existing products as well as materials under development were evaluated and compared for efficacy in management of powdery mildew on cantaloupe in a field trial conducted during the spring of 2006 at the Yuma Valley Agricultural Center. A high level of disease had developed when disease severity data was recorded at crop maturity (Jun 15). Among treatments, the degree of powdery mildew control ranged from 0 to 100%. Among tested products, several are registered for use in Arizona for control of powdery mildew on melons. Using a mixture of products or rotating among efficacious fungicides with different modes of action is important to minimize the development of insensitivity in the pathogen population to one or more of these active ingredients.
    • Examination of Soil Solarization as a Management Tool for Fusarium Wilt of Lettuce: 2005 Field Trial

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006-09)
      Fusarium wilt of lettuce was first recognized in Arizona in 2001. Since this first discovery, the pathogen, Fusarium oxysporum f.sp. lactucae (Fol), has been recovered from infected lettuce plants from approximately 30 different fields. This fungus is a soil-borne pathogen that can remain viable in soil for many years. Cultural disease control measures, such as extended soil flooding and soil solarization, have shown promise in managing Fusarium wilt in other cropping systems. The specific research objective during the 2005 growing season was to further evaluate the effect of preplant solarization of planting beds on subsequent development of Fusarium wilt on lettuce. There was no significant difference between the short (28 days) and long (56 days) solarization period in the subsequent number of diseased lettuce plants; therefore, the disease incidence values for both solarization periods were combined and compared to nonsolarized plots. At each data collection date, the number of lettuce plants showing symptoms of Fusarium wilt was significantly lower in solarized beds compared to nonsolarized beds. At plant maturity (Nov 18), Fusarium wilt had claimed virtually all lettuce plants of the cultivar 'Lighthouse' growing in nonsolarized soil; however, only 19% of lettuce plants of the same cultivar growing in solarized soil showed disease symptoms. This equates to an 81% reduction in diseased plants in solarized soil compared to nonsolarized soil. The results of this field trial suggest that a 30-day summer solarization treatment of lettuce beds can significantly reduce the inoculum of Fusarium oxysporum f. sp. lactucae to levels that would allow substantial growth of a susceptible lettuce cultivar. Additional field studies are needed to refine the solarization process to potentially achieve further increases in efficiency of destroying propagules of Fusarium oxysporum f. sp. lactucae in infested fields.
    • New Challenges to Management of Whitefly Resistance to Insecticides in Arizona

      Dennehy, Timothy J.; DeGain, Benjamin A.; Harpold, Virginia S.; Brown, Judith K.; Morin, Shai; Fabrick, Jeff A.; Byrne, Frank J.; Nichols, Robert L.; Byrne, David N.; Baciewicz, Patti; et al. (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      We report on susceptibility to insecticides of whiteflies (Bemisia tabaci) collected from cotton, melons and ornamental plants during the 2004 season. No major problems with field performance of insecticides against whiteflies were observed or reported in 2004 in Arizona cotton, vegetables, or melons. However, monitoring revealed further statewide reduction in susceptibility to pyriproxyfen (Knack®) and showed that whiteflies possessing pyriproxyfen resistance could be detected in all low desert areas of the state. Susceptibility to buprofezin (Applaud®/Courier®) has not changed significantly since 1997. Mean susceptibility to synergized pyrethroids (e.g., Danitol® + Orthene®) has increased strikingly on a statewide basis since 1995 though highly resistant whiteflies were detected in some collections from cotton, melons and ornamentals. Whiteflies from throughout Arizona continued to be highly susceptible to imidacloprid (Admire®/Provado®). However, susceptibility to the related neonicotinoid insecticide, acetamiprid (Intruder®) varied widely and was lowest in collections from melons and greenhouse plants. Whiteflies from cotton that were least susceptibile to acetamiprid were significantly less susceptible to a second neonicotinoid, thiamethoxam (Actara®/Centric®/Platinum®). The most worrisome findings of our 2004 studies stemmed from detection of a strain of B. tabaci, at a retail nursery, that was essentially unaffected by pyriproxyfen in egg bioassays. It also possessed strikingly reduced susceptibility to acetamiprid, buprofezin, mixtures of fenpropathrin and acephate, imidacloprid, and thiamethoxam. This strain was found to be a biotype of B. tabaci previously undescribed in the US, the Q biotype. We cannot predict with accuracy the timecourse of future resistance problems or the spread and impact of this new whitefly biotype. However, our findings point to the need to formulate contingency plans for management of resistance, in order to insure that Arizona agriculture does not revisit the severe whitefly control problems experienced in the past.
    • Assessment of Fungicide Performance for Management of Downy and Powdery Mildew on Lettuce in 2005

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      Downy mildew, caused by the oomycete pathogen Bremia lactucae, usually can be found in some lettuce fields each year in Arizona. However, both the incidence and severity of the disease are governed by the frequency and duration of cool moist conditions required for disease development. Free moisture on the leaf surface is essential for spore germination and infection, but not growth of this pathogen within the leaf. Powdery mildew on lettuce is caused by the fungus Golovinomyces cichoracearum (Erysiphe cichoracearum). The disease is favored by moderate to warm temperatures and relatively dry weather conditions. Several fungicides were evaluated for their ability to suppress development of downy and powdery mildew on lettuce in 2005. Downy mildew was first observed in plots on February 7, whereas powdery mildew was first detected January 26. The data in the accompanying table illustrate the degree of control obtained by applications of the various materials tested in this trial. Among treatments, the degree of downy and powdery mildew suppression ranged from virtually complete to minimal; however, all treatments significantly reduced the severity of both mildew diseases compared to nontreated plants.
    • Efficacy of Fungicides for Management of Powdery Mildew on Cantaloupe in 2005

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      Powdery mildew occurs annually on melons in Arizona. Podosphaera xanthii (Sphaerotheca fuliginea) is the plant pathogenic fungus that causes powdery mildew on cucurbits, such as cantaloupe, honeydew, watermelon, cucumber and squash. 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. Existing products as well as some materials under development were evaluated and compared for efficacy in management of powdery mildew on cantaloupe in a field trial conducted during the spring of 2005 at the University of Arizona Yuma Valley Agricultural Center. A high level of disease had developed by the time disease severity data was recorded (June 10). Among treatments, the degree of powdery mildew suppression ranged from modest to essentially complete control. All treatments significantly reduced the severity of powdery mildew compared to untreated plants. Relative performance of treatments on the upper leaf surface differed from that on the underside of leaves. The best treatments among all tested fungicides included Quintec, Pristine, BAS517, Procure and Topsin M + Microthiol Disperss. Good levels of disease control were also achieved by Rubigan and Cabrio. The number of marketable cantaloupes was significantly higher in plots where powdery mildew was well controlled compared to untreated plots. Among tested products, several are registered for use in Arizona for control of powdery mildew on melons. Using a mixture of products or rotating among efficacious fungicides with different modes of action is important to minimize the development of insensitivity by the pathogen population to one or more of these active ingredients.
    • Microbial Quality of Iceberg Lettuce is Affected by Moisture at Harvest - 2nd Year Evaluation

      Fonseca, Jorge; Byrne, David N.; Baciewicz, Patti; The University of Arizona - Yuma Agricultural Center (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      In a continuing work, the effect of moisture conditions on yield and microbial quality of Iceberg lettuce was investigated. Iceberg lettuce cv. Sahara grown at the University of Arizona Yuma Agricultural Center was evaluated for yield, microbial population and postharvest quality either following different irrigation termination schedules or before/after a rainfall event. We report here microbial population data with treatments including early (16 days before harvest), middle (8 days before harvest) and late (4 days before harvest) irrigation termination. Lettuce receiving the last irrigation 4 days before harvest showed increased weight but had higher microbial population than other treatments. The effect of moisture prior to harvest on quality was further evaluated with lettuce harvested before and after a rainfall event. Increased aerobic bacteria population of over 1 log CFU/g for outer leaves and over 2 log CFU/g for head leaves was observed after rain. The results from this study suggest that managing moisture conditions at harvest is important to enhance quality of lettuce.
    • Evaluation of AuxiGro® WP on Cantaloupe Production in the Low Desert

      Rethwisch, Michael D.; Reay, Mark; Grudovich, Jessica L.; Wellman, Jessica J.; Ramos, David M.; Hawpe, Erica; Berger, Lois; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      AuxiGro® WP was applied to three cantaloupe fields in the Palo Verde Valley of far eastern California in the spring of 2004. One field utilized evaluated high rates (3.4x higher than other fields for each rate) of AuxiGro® WP for the purposes of phytotoxicity observations, while either a single application or two applications of varying rates of AuxiGro® WP were applied in the other two fields respectively. No visual symptoms of phytotoxicity were noted for AuxiGro® WP in any of the fields where applied, including two honeydew fields in the fall of 2003. Applications of any rate of AuxiGro® WP did not result in a statistical increase in numbers of melons from either a single or a double application on either variety (Ranger, Topmark respectively) used for yield data in this experiment. Data indicated that statistical differences existed for some melon parameters between treatments means in the hybrid variety (Ranger) but these statistical differences were not present for most fruit parameters in the open pollinated variety (Topmark), although some of the same trends were noted. These differences may be due to differing lengths of time from application to harvest. Of only the four rates of AuxiGro® WP evaluated, the heaviest melons were noted in the 4 oz./acre rate followed by the 8 oz./acre rate in both cantaloupe varieties, with this rate resulting in slightly heavier cantaloupes than the untreated check in both varieties. The one oz./acre rate of AuxiGro® WP also resulted in slightly shorter and lighter melons for both varieties than did application of only Solar™, but brix was numerically higher for this rate of AuxiGro® WP than for the Solar™ treatment. The two lowest mean brix were noted from in both cantaloupe varieties treated by Solar™ treatment alone and the 4 oz./acre rate of AuxiGro® WP + CalMax treatment, with these means being statistically less than the untreated check in 'Ranger' cantaloupes. CalMax by itself resulted in slightly smaller melons than the untreated check in both melon varieties. The AuxiGro® WP + CalMax treatment resulted in the largest melons (both longest and widest) of any treatment in the 'Ranger' cantaloupe field, with the difference in length being statistically greater than CalMax alone. Although larger melons would normally be thought to ripen earlier and therefore have higher brix readings, usage of AuxiGro® WP in combination with CalMax is thought to reduce stress as plants are still quite actively growing, hence the lower brix readings.
    • Effectiveness of Contans and Serenade Within a Biologically Intensive Integrated Pest Management System for Sclerotinia Drop on Lettuce: 2005 Study

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      Sclerotinia drop of lettuce, caused by the pathogenic fungi Sclerotinia minor and S. sclerotiorum, is a serious disease in most regions where this crop is grown. Conventional fungicides, such as Rovral (iprodione) and Endura (boscalid), are usually applied after lettuce is thinned and once more 2 to 3 weeks later. Two biological products, Contans (Coniothyrium minitans) and Serenade (Bacillus subtilis), are also available. In earlier field trials conducted from 2001 to 2003 in the presence of S. sclerotiorum, the mean reduction in disease by Contans, Serenade and Endura was 69, 18 and 41%, respectively. The objective of the current study was to determine the efficacy of the biological products Contans and Serenade, applied alone or in combination with each other or the conventional fungicide Endura, within a biologically intensive integrated pest management system for Sclerotinia drop on lettuce. The study was conducted at The University of Arizona, Yuma Valley Agricultural Center. Sclerotia of Sclerotinia sclerotiorum were produced in the laboratory. Lettuce ‘Winterhaven’ was seeded and sclerotia were applied to the plots on November 8, 2004. Disease assessment was performed three times, including plant maturity (February 24), by recording the number of dead plants in each plot. Lettuce drop caused by Sclerotinia sclerotiorum was significantly reduced by the biofungicides Contans and Serenade as well as the conventional fungicide Endura. At plant maturity, the highest level of disease control among all treatments was provided by one or two applications of the biofungicide Contans as well as application of Contans at seeding following by either Serenade or Endura after thinning. Also, two applications of the other tested biofungicide, Serenade, controlled Sclerotinia drop as well as two applications of the conventional fungicide, Endura. The results of this study suggest that the biological products Contans and Serenade, used either alone or with the conventional fungicide Endura, can provide effective levels of control of lettuce drop caused by S. sclerotiorum. Although encouraging, the results from this initial field trial will need to be confirmed by additional studies. Funding for this research project was provided, in part, by the IR-4 project under a cooperative agreement with the U.S. Environmental Protection Agency.
    • Effects of Foliar Applied Fertilizers on Yield and Quality of Late Spring Cantaloupes and Honeydews

      Rethwisch, Michael D.; Perez, Rogellio; Morrison, Steven; Parker, Larry; Juan, Julio; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      A number of foliar fertilizers were evaluated for their effects on yield and quality of both cantaloupes and honeydews. None of the treatments or treatment combinations resulted in statistical increases or decreases for numbers of cantaloupes or honeydews when compared with the untreated check. A highly significant increase of one treatment regimen (which contained calcium) was noted for cantaloupe weights when compared with the untreated check. Statistical differences were not noted for honeydew weights for this treatment although it also resulted in highest calculated weights of honeydew/area of treatments evaluated. All treatments resulted in numerically higher brix for cantaloupes than the untreated check, thought to be a response to pounds of melons/unit area as the untreated check had the least cantaloupe weight. No differences were noted for cantaloupe seed cavity diameters.
    • Effect of Fungicides on Development of Root and Crown Rot on Chile Pepper Plants Grown in Field Soil Naturally Infested with Phytophthora capsici

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      Phytophthora blight of peppers (Capsicum annuum) is caused by the oomycete pathogen Phytophthora capsici. In Arizona, the root and crown rot phase of the disease initially can appear on plants early in the growing season in areas of the field where soil remains saturated with water after an irrigation. Disease severity can increase dramatically due to summer rains during July and August in the southeastern Arizona production area. The efficacy of the systemic fungicide mefenoxem (Ridomil Gold)) for control of Phytophthora blight on pepper has been documented; however, in many pepper production regions, populations of the pathogen insensitive to this fungicide have developed. Other chemistries, including dimethomorph (Acrobat) as well as two new fungicides in development (Ranman and TM-459) have activity on some species of Phytophthora and associated diseases on crops other than pepper. The objective of the following trials was to evaluate and compare the effects of soil drench treatments with Ridomil, Acrobat, Ranman and TM-459 alone, as well as in combination treatments on subsequent development of root and crown rot on chile pepper plants grown in soil naturally infested with P. capsici. Three separate trials were conducted in the greenhouse. Usually, the top fresh weight of plants treated with an appropriate amount of Ranman, TM-459, or Acrobat did not differ from plants grown in sterilized soil. On the other hand, the top fresh weight of plants treated with Ridomil Gold often was not significantly different from plants grown in untreated infested soil, implying that this soil contained a population of Phytophthora capsici that is insensitive to this fungicide. These trials suggest that soil application of Ranman and TM-459 could effectively inhibit the development of Phytophthora root and crown rot on chile peppers grown in soil infested with Phytophthora capsici.
    • Comparative Evaluation of Products to Manage Sclerotinia Drop of Lettuce in 2005

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      Sclerotinia drop on lettuce is caused by two soil-borne fungi, Sclerotinia minor and S. sclerotiorum. Moist soil and moderate temperatures favor this disease. Some registered products as well as new chemistries in development were compared for their ability to suppress Sclerotinia drop on lettuce during the winter vegetable growing season in 2004-2005. Sclerotia of each pathogen were incorporated into plots after lettuce thinning and just before the first application of test compounds. In plots infested with either Sclerotinia minor or S. sclerotiorum, most materials tested at an appropriate rate significantly reduced disease. In plots infested with S. minor, the best treatments included Endura, Endura followed by Rovral, Botran, and Endura + Contans. For plots containing S. sclerotiorum, the best treatments included Endura + Contans, Endura followed by Rovral, and Contans. One of the products tested, Contans, is a biological control material. For a valid comparison of products for control of Sclerotinia drop of lettuce, it is important to compare the results obtained from more than one field study. The reader is urged to review previous studies in addition to this report to get an accurate picture of the relative efficacy of tested compounds for control of Sclerotinia drop.
    • Evaluation of a New Harpin Product on Microbial Quality and Shelf Life of Minimally Processed Lettuce

      Fonseca, Jorge; Kline, Wesley L.; Wyenandt, Christian A.; Hoque, Mushidul; Ajwa, Husein; Byrne, David N.; Baciewicz, Patti; The University of Arizona - Yuma Agricultural Center; Rutgers Cooperative Extension - Bridgeton, NJ; University of California, Davis /USDA-ARS, Salinas CA (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      The effect of pre-harvest application of Extend®, a newly developed second generation harpin product, on shelf life of fresh-cut lettuce was investigated. The lettuces were grown in locations A: Watsonville, CA; B: Cedarville, NJ; and C: Yuma, AZ, and treated five days before harvest at 30, 60 and 90 ppm (2,4 and 6 oz/acre in 50 gal/acre). Lettuce processed and bagged was stored at 34-37°F and evaluated for quality for 20 days. Lettuce from trial A treated with 60-90 ppm harpin consistently had a better overall quality and lower microbial population than the control. Results from trial B showed no differences among treatments. In trial C, microbial population was lower and visual quality higher in lettuce treated at 60 ppm than the control during early stages of storage. Overall results are mixed but it was revealed that a field application of harpin can improve quality of fresh-cut lettuce under conditions that need to be determined.
    • Yield and Postharvest Quality of Cantaloupe Melons as Affected by Calcium Foliar Applications

      Fonseca, Jorge; Byrne, David N.; Baciewicz, Patti; The University of Arizona - Yuma Agricultural Center (College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005-12)
      The effect of pre-harvest foliar application of calcium on yield and postharvest quality of whole and fresh-cut cantaloupe melons was investigated. The calcium product (Nutrical®) was applied five times before harvest to a melon field at 2 quarts/acre with a volume of 50 gallons/acre. The supplemented calcium increased by over 10% the weight of melons and increased external firmness at harvest but soluble solids was lower in treated melons than in the control. After 21 days of storage at 40 - 45 °F however, there was not difference in quality factors. Melons were processed in cubes and packaged in plastic lidded containers. The overall quality of calcium treated cubes was better after 5 and 10 days of storage. Juice leakage was also higher in the control than in the treated fruits after 5 days. After 10 days the L* values were lower in the control than in the treated fruits indicating that the tissue was darker in the control, which was an indicative of more water soaked tissue. In further trials conducted the following Spring the results obtained at harvest showed differences only in weight of melons that underwent water stress. The overall results in different experiments in the Yuma area indicate that application of foliar calcium can increase yield of melon crops, notably, when the plants undergo environmental stress.