• Effects of Cotton Ginning and Lint Cleaning on Sticky Cotton

      Henneberry, T. J.; Hendrix, D. L.; Perkins, H. H.; Silvertooth, Jeff; USDA, ARS Western Cotton Research Laboratory, Phoenix AZ; USDA, ARS, Cotton Quality Research, Clemson, SC (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Ginning and lint cleaning effects on cotton stickiness were minimal but reduced amounts of trehalulose and reduced thermodetector counts occurred following each lint process Leaf trash from ginned seed cotton contained trehalulose and melezitose. Removal of leaf trash in ginning and lint cleaning probably accounts for some reduced lint stickiness.
    • Effects of Entomopathogentic Nematodes on Pink Bollworm Mortality

      Henneberry, T. J.; Forlow Jech, L.; Burke, R. A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Steinernema riobravis Cabanillas, Poinar & Raulston infected pink bollworm Pectinophora gossypiella (Saunders), larvae over a temperature range of 15.6 - 38.0° C. Temperatures of 32.2° C and higher and exposure for 48 h or more often resulted in decreased numbers of nematode killed larvae with living nematodes and increased numbers of dead larvae with dead or no nematodes.
    • Efficacy of Experimental Insecticides for Insect Control in Cotton Grown in the Low Desert Region of Arizona, 1997

      Kerns, David L.; Tellez, Tony; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Experimental insecticides were evaluated for control of lygus bugs relative to commercial standards in cotton. These products were also evaluated for activity towards whiteflies and pink bollworms. CGA293343 was not effective when used as a side-dress material at layby, but was effective toward whiteflies, and towards lygus at higher foliar rates. Regent, Vydate and Mustang + Thiodan were highly effective for lygus control, while EXP61096A and Mustang alone performed poorly. Against whiteflies, CGA293343, Acetamiprid, and Mustang + Thiodan were most efficacious, while Mustang alone and with Thiodan were most effective towards pink bollworms.
    • Efficacy of Experimental Insecticides for Whitefly Control in Cotton, 1996

      Kerns, David L.; Tellez, Tony; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Experimental insecticides were evaluated for control of sweet potato whiteflies relative to a commercial standard in cotton. Ni-25 provided excellent whitefly control and was equivalent to the commercial standard (Knack followed by Danitol + Orthene). Fenoxycarb + pymetrozine provided goodwhitefly control but seemed to require 2 sequential applications before control was equivalent to Ni-25. Diofenolan + pymetrozine appeared to be a slightly weaker treatment, but still provided acceptable whitefly control.
    • Efficacy of Experimental Insecticides for Whitefly Control in Cotton, 1997

      Kerns, David L.; Tellez, Tony; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Whitefly populations in this trial were abnormally low relative to previous years experiences. M-25 provided excellent whitefly control and was equivalent to the commercial standard (Knack followed by Danitol + Orthene). However, there is some question concerning its adult activity late in the season, when it appeared to be weaker than Danitol + Orthene and Capture + Curacron. At low whitefly populations Thiodan tank -mixed with Knack appeared to extend control over Knack alone.
    • Efficacy of Insecticides for Pink Bollworm and Cotton Leaf Perforator Control in Cotton Grown in the Low Desert Region of Arizona, 1997

      Kerns, David L.; Tellez, Tony; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Neither Tracer nor Proclaim appeared to be effective pink bollworm materials whether applied at day or night. However against cotton leafperforator, both Tracer and Proclaim provided sufficient control. Although all three formulations of Karate equally provided statistically significant pink bollworm control, it was not commercially acceptable. Shortening the spray interval from 7 to 4 days may have helped alleviate this problem. None of the Karate formulations evaluated appeared to offer outstanding cotton leafperforator control.
    • Evaluation of 1997 Late-Season Crop Conditions

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      In the latter part of the 1997 season (August) many fields across Arizona, from Marana to the Mohave Valley, were experiencing premature senescence. In an effort to evaluate the conditions leading to the symptoms and to possibly determine the causes, an extensive series of field examinations were conducted in a number of representative fields in central Arizona. Soil samples were taken from selected fields that ranged in expression of the symptoms from very light to severe. Complete analyses of the soil samples were conducted. Plant tissue samples were also collected and analyzed for plant nutrient levels. No absolute causal agent was identified. However, a factor believed to be of significance was that of low soil K levels, where many of the fields expressing the most severe symptoms also had low soil K levels. It is also important to consider the fact that plants exhibiting K deficiency are very similar in appearance to plants affected by Verticillium wilt, which also appeared to be a primary or contributing factor in many cases.
    • Evaluation of a Feedback Approach to Nitrogen and Pix Applications, 1997

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A single field experiment was conducted in 1997 at Marana, AZ to compare a scheduled approach (based on stage of growth) versus a feedback approach (based on growth parameters) to both nitrogen (N) and mepiquat chloride (P1X) applications on Upland cotton (Gossypium hirsutum L.). PIX feedback treatments were based upon fruit retention (FR) levels and height to node ratios (HNRs) with respect to established baselines for Arizona growing conditions. Scheduled and feedback FIX applications were made for a total of 0.75 and 1.50 pt./acre, respectively, with the scheduled treatments being initiated earlier in the fruiting cycle (early and peak bloom). Feedback PIX treatments consisted of a single 0.75 pt./acre application near peak bloom (approx. 2000 heat units after planting, HUAP, 86/55 °F threshold). Scheduled applications of fertilizer N totaled 150 lbs. N/acre from two applications and feedback N treatments received a total of 100 lbs. N/acre from two applications. Treatments consisted of all combinations of scheduled or feedback applications of both N and PIX. The highest lint yields were from treatments receiving PIX applications, with significant differences (P ≥ 0.05) between a check treatment (with no FIX applications) and several other treatments that did receive PIX applications. If FIX was applied, there were no significant differences between the scheduled or feedback approach. Applications of PIX in relation to increasing HNRs (feedback approach) are demonstrated and reinforced in this study.
    • Evaluation of a Nitrogen-15 Microplot Design in a Furrow Irrigated Row Crop System

      Silvertooth, J. C.; Navarro, J. C.; Norton, E. R.; Sanchez, C. A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Two field experiments were conducted in Arizona in at two locations, Maricopa in 1991 (Casa Grande sandy loam) and Marana (Pima clay loam) in 1995. The purposes of the experiments were to evaluate the dimensions of an ¹⁵N microplot design used in a furrow irrigated row crop system. The experiments each utilized ammonium sulfate fertilizer with 5 atom % ¹⁵N enrichment applied at a rate of 56 kg N/ha in simulated side-dress band application during the early bloom stage of development of Upland cotton (Gossvpium barbadense L). At each location, microplots were 4, 1.02 m rows wide and 1.00 m in length. Whole plant samples were collected at specific locations within and near the microplots. Uptake of ¹⁵N by plants was uniform within microplots but declined symmetrically in relation to microplot borders. Collection of plant materials within 25 cm of microplot borders provided uniform ¹⁵N enrichment levels for determining fertilizer N uptake and recovery. Use of microplots with the dimensions of those used in this study are sufficient for collecting plant materials from a 1 m² area; consisting of two, 50 cm segments from the interior two rows of the four row microplot. This also allows for sufficient distance from the perimeter of the microplot to account for border effects.
    • Evaluation of B. T. Cotton Deployment Strategies and Efficacy against Pink Bollworm in Arizona

      Simmons, A. L.; Dennehy, T. J.; Tabashnik, B. E.; Antilla, L.; Bartlett, A.; Gouge, D.; Staten, R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A multi- agency team in Arizona in 1997 evaluated B.t. cotton deployment strategies in a large field trial; conducted statewide monitoring of pink bollworm (PBW) susceptibility to the Cry1Ac endotoxin, and established a Rapid Response Team that investigated claims of unacceptable performance of B.t. cotton. Though needing further evaluation, in-field refuges of one row of non-B.t. cotton for each five rows of B.t. cotton showed promise as an alternative to the current recommendation of external refuges for planting B.t. cotton. Preliminary results of statewide monitoring showed that four field populations were more susceptible to Cry1Ac than were two reference susceptible laboratory strains. A strain of PBW previously reported to be resistant to CrylAc was confirmed to be significantly less susceptible to this toxin than were the two susceptible laboratory strains or the four field populations tested. The Rapid Response Team, based at the Arizona Cotton Growers Association, investigated nine reports of unusual larval survivorship in B.t. cotton. Only one of these, which has been placed in culture, was confirmed to have resulted in substantial numbers of large larvae surviving in bolls of putatively B.t. cotton. Further investigations of this population and the plants from which it was derived are underway.
    • Evaluation of Calcium Soil Conditioners in an Irrigated Cotton Production System, 1997

      Griffin, J. R.; Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A single field experiment was conducted at Paloma Ranch, west of Gila Bend in Maricopa County Arizona in 1996 and 1997. NuCotn™ 33B was dry planted and watered -up on 15 April and 1 April in 1996 and 1997. Various rates and times of application of nitrogen (N) and calcium (Ca) from two sources [N-Cal™ (CO(NH₂)₂•CaC1₂) and CAN-17 (CaNO₃)] as well as a standard N source, UAN-32 [NH₄NO₃•CO(NH₂)₂] were used to evaluate the check In 1996 treatments 1, 2,and 3 each received a total of 280 lbs. N/acre, treatment 4 received a total of 210 lbs. N/acre, while treatment 5 received a total of 301 lbs. N/acre. Treatment 1 received only farm standard applications of UAN-32. Treatments 2 and 4 each received a total of 72 lbs. of Ca/acre. Treatment 5 received a total of 79 lbs. Ca/acre from N-Cal™ while treatment 3 received a total of 301 lbs. Ca/acre from CAN -17. Treatment 4 used a conservative N approach (UA guidelines). 1997 was similar to 1996 in the general nature of the experimental design, but different in its actual treatments. Treatments 2, 3, 4, and 5 each used N-Cal™ for the first two irrigation applications then UAN -32 for continued crop N needs. Treatment 4 used a conservative N approach (U A guidelines). Treatments 3 and 5 each received two foliar applications of N-Cal™ Foliar applications consisted of N-Cal™ mixed with urea for a 15-0-0-8 formula and applied on 22 July and 29 July via a high cycle applicator at a 5 gal/acre rate of N-Cal™ (carrier rate = 40 gal /acre). No significant differences were found among the various treatments in terms of plant growth, soil water content, ECₑ values, and sodium absorption ratios in 1996 or 1997. Lint yields were not significantly different in 1996 (P < 0.05) or 1997 (P < 0.05).
    • Evaluation of Irrigation Termination Affects on Upland Cotton, 1997

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A single field study was conducted in 1997 at the Maricopa Agricultural Center (1,175ft. elevation) to evaluate the effects of three dates of irrigation termination on the yield of a common Upland cotton variety (DP NuCOTN 33b). Planting date was 9 April (668 HU /Jan 1 86/55° F thresholds. Three dates of irrigation termination (IT1, IT2, and IT3) were imposed based upon crop development into cut -out. The earliest irrigation termination date, IT1 (7 August) was made as early as possible in an attempt to provide sufficient soil - water such that bolls set at the end of the first fruiting cycle would not be water stressed and could be fully matured. The second termination (IT2) date was 20 August, and provided one additional irrigation over IT1. The final (IT3) date was 17 September, which was staged so that soil moisture would be sufficient for development of bolls set up through the last week of September and provide full top-crop potential. Lint yield results revealed no differences among any of the IT treatments. Mirconaire values increased slightly with later IT dates.
    • Evaluation of Planting Date Effects on Crop Growth and Yield for Upland and Pima Cotton, 1997

      Silvertooth, J. C.; Norton, E. R.; Brown, P. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Three field studies were conducted in 1997 at the Maricopa (1,175 ft. elevation) and Marana (1,974 ft. elevation Agricultural Centers to evaluate the effects of three planting dates on yield and crop development for three representative Upland varieties. Planting dates ranged from 13 March to 8 May and also 312-1159 HU/Jan 1 (86/55° F thresholds). Crop monitoring revealed increased vegetative growth tendencies with later plantings. General trends also showed decreasing lint yield with the later plantings for all varieties at each location.
    • Field Determination of Permanent Wilting Point

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Water is a vital resource for cotton production in the desert Southwest. One method of managing irrigation water is through the use of a "checkbook" approach to irrigation scheduling. This involves irrigating based upon the percent depletion of plant available water (PA its from the soil profile. In order to effectively utilize this method of irrigation scheduling soil water content values at field capacity (FC) and permanent wilting point (PWP) must be defined. In this study the PWP values were characterized for two different soil types, one at Maricopa, AZ and another at Marana, AZ. The possibility of having different values for PWP as a function of crop stage of growth was also investigated in this study. Results demonstrated differences in both FC and PWP values between the two locations. Differences were also observed as a function of crop growth stage in the pattern of soil water extraction at the Maricopa location.
    • Foliar Fertilizer Evaluation on Upland Cotton, 1997

      Silvertooth, J. C.; Norton, E. R.; Ozuna, S. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A single field experiment was conducted in 1997 at the University of Arizona Yuma Valley Agricultural Center. The purpose of the experiment was to evaluate foliar applications of Macro Sorb (L form amino acids) and KeyPlex (chelated micronutrients and alpha keto amino acids) foliar fertilization materials on Upland cotton. Treatments consisted of various rates and times of application of the foliar materials based upon manufacturer recommendations. Results from this single experiment revealed no differences among treatments with respect to in-season plant measurements, tissue N concentrations, or lint yield.
    • Fruiting Distribution Patterns among Three Cotton Varieties under Irrigated Conditions

      Ozuna, S. E.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A field experiment was conducted at the UA Maricopa Agricultural Center (MAC) to determine the fruiting distribution patterns of two commonly grown Upland cultivars, DP 33b and DP 5415, and one American Pima cultivar, Pima S-7. Results indicate that cotton plants (G. hirsutum L. and G. barbadense L.) produce total yield at fruiting branches one through 18, with the majority of yield occurring at fruiting branches one through 12. Among fruiting branches one through 12, the majority of yield is occurring at fruiting positions one and two. These results indicate that the bulk of the yield is produced early in the season and declines as the season progresses
    • Fungicide Treatment and Varietal Effects on Alternaria Leaf Spot of Pima Cotton

      Olsen, Mary W.; Clark, Lee; Moser, Hal; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      The effect of foliar treatments for prevention of Alternaria leaf spot was evaluated in the field on six varieties of Pima cotton. Disease was significantly reduced by protective sprays of mancozeb and micronized sulfur but not by foliar applications of urea in trials at the University of Arizona Safford Agricultural Center in Safford, AZ. Treatments had no significant effects on yields. Significantly fewer lesions developed on Pima variety UA 4 than on the other varieties. Disease pressure was relatively light, and even though scheduled preventive sprays with mancozeb were effective, fungicide applications probably would not increase yields under the environmental conditions of this experiment.
    • Infection of Sorghum Varieties by the Cotton Root-knot Nematode, Meloidogyne incognita

      McClure, M.; Husman, S.; Schmitt, M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Twentythree varieties of sorghum, Sorghum bicolor, were evaluated for susceptibility to the cotton root -knot nematode, Meloidogyne incognita race 3. Eggs per gram of root were used as a measure of nematode reproduction and host susceptibility. The nematode reproduced on all varieties tested Mean egg counts were lowest on the varieties Northrup King (NK) KS-737, MF.; NK 1580,M; NK Ks-735 M.F.; NK 714Y MF.; NK Lt. Bronze X 609 M; Ciba-NK C-1506, M; and Pioneer 8877, but these varieties are still considered to be hosts capable of sustaining or increasing nematode populations in cotton fields. All varieties were better hosts than cotton.
    • Integrated Lygus Management in Arizona

      Ellsworth, Peter C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Integrated Lygus management depends on the same fundamentals of management for any pest. There needs to be a system of monitoring (sampling), understanding of the density-yield relationship (thresholds) and other insecticide optimization practices (e.g., resistance management), and a plan for reducing the chance of infestation and need for remedial measures (avoidance). While all these guidelines are under current study, current recommendations represent a fundamental base on which to build an integrated Lygus management program that will also manage for susceptibility to our current insecticides. Key to this sustainable susceptibility system is limiting insecticide use to the lowest practical levels. This is best accomplished by careful sampling, careful assessment of thresholds and selection of the right compound for the job, but, most of all, avoidance of the problem from the start. Current recommendations are detailed below in light of the most recent research findings.
    • Interactions Between Herbicides and Cotton Seedling Damping-off in the field

      Heydari, A.; Misaghi, I. J.; Silvertooth, Jeff; Department of Plant pathology, University of Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      We studied the impact of three pre plant herbicides, trifluralin, pendimethalin and prometryn on the incidence and the development of Rhizoctonia solani- induced cotton seedling damping-off in the field. In a field experiment conducted in Safford, Arizona, pre plant application of pendimethalin or prometryn but not trifluralin caused significant (P < 0.05) increases in disease incidence. In another field experiment in Tucson, Arizona, significant (P < 0.05) increase in disease incidence was observed in plots treated with prometryn and not in those treated with pendimethalin and trijuralin. In Tucson field experiment, application of herbicides also affected disease development as judged by the slope of disease progress curves.