• Nematodes and Their Control in Upland Cotton

      Husman, S.; Wegener, R.; McClure, M.; Schmitt, M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Cotton fields from 133 townships in 7 Arizona counties were surveyed for nematodes. Plant parasitic species were found in all fields sampled. Lesion nematodes (Pratylenchus spp.) were found in 33% of the samples and Root-knot nematodes (Meloidogyne spp.) were found in 35% of the samples. Field trials in Pinal Coiunty were conducted in 1998, 1999, and 2000 to determine the impact of nematode control on the yield of Upland cotton. Telone II® increased lint production in 20 of 24 trials.
    • Influence of Ironite and Phosphorus on Long and Short Cotton on the Safford Agricultural Center, 2000

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Ironite and phosphorus were applied as a combined treatment and also individually to plots planted to long and short staple cotton to find their effect on crop development and lint yield. A statistically significant increase in lint yield was seen with 14 pounds of Ironite and 200 pounds of 16-20-0 per acre compared with the untreated check in the short staple plots. An increase in long staple yield was observed as the Ironite treatment increased from 7 to 28 pounds per acre when coupled with 200 pounds of 16-20-0. Few differences were seen between treatments in any of the plant mapping variables measured or with HVI values. More research and an economic analyses are needed to determine if this would be a recommended procedure in the Safford valley.
    • Defoliation of Pima and Upland Cotton at the Safford Agricultural Center, 2000

      Clark, L. J.; Coleman, R. D.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Nine defoliation treatments based on defoliating agents that are in use in the area plus two additives (compounds A, B) were applied to Pima and Upland cotton to compare the treatment effects on percent leaf drop and yields. All of the treatments were beneficial to leaf drop compared to the untreated check with the Ginstar treatments generally performing better than the chlorate. One of the additives enhanced the early defoliation effectiveness of chlorate, the other additive enhanced the effectiveness of Ginstar throughout the defoliation process. More studies will be needed before recommendations can be made.
    • N Volatilization from Arizona Irrigated Waters

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A laboratory study was initiated to investigate the potential loss of fertilizer nitrogen (N) through volatilization at four different temperatures (25, 30, 35, and 40°C) out of irrigation waters collected from a number of Arizona locations. Complete water analysis was conducted on each of the water samples. A 300 ml volume of each water was placed in 450 ml beakers open to the atmosphere in a constant temperature water bath with 10 mg of analytical grade (NH₄)₂SO₄ added to each sample. Small aliquots were drawn at specific time intervals over a 24 hour period and then analyzed for NH₄⁺-N concentrations. Results showed potential losses from volatilization to be highly temperature dependent. Total losses (after 24 hours) ranged from 30-48% at 25°C to over 90% at 40°C. In this study where (NH₄)₂SO₄ was used as the N source, the initial concentration of SO₄⁻-S in the solution had a repressive effect on volatilization due to the decreased availability of free NH₄⁺ in waters with high initial SO₄⁻-S concentrations due to the formation of complex ion pairs (NH₄SO₄⁻). It was also observed that at lower temperatures complexation and ion pair formation affected volatilization of NH₃ by reducing the NH₄⁺ activity in solution and thereby reducing NH₃ volatilization. Potential volatilization loss of fertilizer N from these irrigation waters was found to be significant and should be considered when making decisions regarding fertilizer N applications for crop production in Arizona.
    • Evaluation of Irrigation Termination Effects on Fiber Micronaire and Yield of Upland Cotton, 2000

      Silvertooth, J. C.; Galadima, A.; Norton, E. R.; Moser, H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Arizona has experienced a trend toward increasing fiber micronaire values in recent years resulting in substantial discounts on fiber value. There is some evidence to suggest that irrigation termination management can impact fiber micronaire. A single field study was conducted in 2000 at the Maricopa Agricultural Center (1,175ft. elevation) to evaluate the effects of three dates of irrigation termination on the yield of 13 Upland cotton varieties. Planting date was 6 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 cutout. The earliest irrigation termination date, IT1 (24 July) was made slightly ahead of an optimum date 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. Thus, the IT1 date was imposed to try to reduce overall micronaire. The second termination (IT2) date was 17 August, and provided one additional irrigation over an optimal point for the first cycle fruit set and two irrigations beyond IT1. The final (IT3) date was 15 September, which was staged so that soil moisture would be sufficient for the development of bolls set up through the last week of September thus providing full top-crop potential. Lint yield and micronaire results revealed significant differences among the IT treatments. Micronaire and lint yield values increased with later IT dates.
    • Recent Yield and Fiber Micronaire Tendencies for Upland Cotton in Arizona

      Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Problems associated with increasing trends towards high micronaire values for Upland cotton (Gossypium hirsutum L.) have been a matter of concern for the Arizona cotton industry in recent years. The discounts on fiber value associated with high micronaire has been compounded by the fact that market prices for cotton fiber has been very low in recent years and yields have been stable at best. An evaluation of recent yield and fiber quality data from a number of locations in Arizona was evaluated in relation to trends within Arizona and across the U.S. cotton belt. Results indicate similar patterns exist in terms of stable yields (yield plateau) and increasing micronaire values between Arizona and other U.S. cotton producing states. The conclusion is presented that these patterns are at least due in part to a common genetic base for varieties that grown in Arizona and beltwide. There also appears to be some distinct relationships associated with high micronaire with region and individual farm management practices.
    • Acala Cotton Variety Trial, Safford Agricultural Center, 2000

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Eighteen Acala cotton varieties were tested in a replicated small plot trial on the Safford Agricultural Center in Graham county at an elevation of 2950 feet. The highest yielding variety in this study was Hazera 195-208, an interspecific hybrid from Israel, with a yield of 1387 pounds of lint per acre. It was followed closely by two varieties from New Mexico, 1517-99 and B7514. Hazera 195-208 had the highest yield in an interspecific hybrid study and 1517-99 was the highest yielding Acala variety in the Upland cotton regional variety trial in 1999 (1). The next five varieties consisted of two interspecific hybrids from Israel, a variety from Buttonwillow Research and two advanced strains from New Mexico. Yield and other agronomic data as well as fiber quality data are contained in this paper.
    • Arizona Upland Cotton Variety Testing Program, 2000

      Moser, H.; Hart, G.; Clark, L.; Husman, S.; Clay, P.; Zerkoune, M.; Guerena, M.; Silvertooth, J.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Each year the University of Arizona conducts variety trials across the state to evaluate the performance of upland cotton varieties. These tests provide unbiased data on the performance of varieties when tested side-by-side under typical production practices. In 2000, we planted a total of ten trials, one in the southwestern region (Yuma county), six in the central region (MoHave, La Paz, Maricopa, and Pinal counties), one in the southern region (Pima county), and two in the eastern region (Graham and Cochise counties). We tested six to ten commercially available varieties in each test. The purpose of this report is to present the results of our 2000 tests conducted in southwestern, central and southern Arizona. Lee Clark presents results from eastern Arizona in two companion reports in this publication. The results show that many varieties performed well at several locations, indicating good adaptation to Arizona conditions. The highest yielding varieties did not always produce the most value per acre, clearly demonstrating the importance of both yield and fiber quality in determining the value of the crop. Growers should carefully weigh the costs and benefits of yield, quality, and transgenic technology when selecting varieties.
    • Continuing Investigations in Ultra-narrow Row Cotton, Safford Agricultural Center, 2000

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      The continuing investigation in ultra-narrow row cotton production has not produced a definitive answer to whether this practice would be economically feasible in this area. Results of this season showed that planting two seed rows on a bed can produce yields in excess of those yields produced with a single seed row, where the plant populations are comparable. This configuration can be harvested with a conventional spindle picker. Plant mapping data and HVI data are shown for all treatments in this study.
    • Pima Cotton Regional Variety Trial, Safford Agricultural Center, 2000

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Twenty five long staple varieties were tested in a replicated small plot trial on the Safford Agricultural Center in Graham county at an elevation of 2950 feet. The highest yielding variety in this study was Hazera 83-208 with a yield of 1180 pounds of lint p1er acre. This interspecific hybrid from Israel was the highest yielding cultivar in the 1999 test, also. The top five varieties consisted of two interspecific hybrids from Isreal, a variety developed by the University of Arizona and entries from Buttonwillow Research and California Planting Cotton Seed Distributors (CPCSD). The average yield in the trial was the same as last year, but the highest yield was slightly lower. Yield and other agronomic data as well as fiber quality data are contained in this paper.
    • Heat Stress and Cotton Yields in Arizona

      Brown, Paul W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Yield of upland cotton was related to heat stress in Yuma, LaPaz, Maricopa, and Pinal Counties for the period 1987-1999. Heat stress during the primary fruiting cycle was assessed using heat stress units (HSU) which were derived from mean daily canopy temperatures computed using a canopy temperature model and local AZMET weather data. Mean lint yields were computed for years with low, intermediate and high levels of HSU. Yields in years with low levels of heat stress were always significantly greater than yields in years with high levels of heat stress. Differences in yield between high and low heat stress years ranged from 100 lb/a in Maricopa County to 254 lb/a in Yuma County and averaged 166 lb/a across all counties. Differences in yield between the low and intermediate stress years, and intermediate and high stress years averaged 86 and 80 lb/a, respectively across all counties; however, these differences were not always significant in individual counties.
    • Short Staple Variety Trials, Graham County, 2000

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      One replicated on-farm short staple variety trial was planted in Graham County in 2000. Ten varieties were evaluated on the Larson farm in Thatcher. Several new varieties were planted in these studies, including 5 transgenic varieties, 3 varieties from Buttonwillow Research in California, and the newest acala from New Mexico. The Australian variety, FiberMax 989, produced the highest yield with 895 pounds of lint per acre. Paymaster 1560 BRR and DPL 655BRR followed close behind and were not separable statistically from the leader. Yield and other agronomic data are reported by variety along with HVI values from the lint.
    • Evaluation of Narrow and Ultra Narrow Cotton in Arizona

      Clay, P. A.; McCloskey, W. B.; Husman, S. H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A field experiment was conducted in 2000 to evaluate narrow (30") and ultra narrow (10") row spacing cotton production systems. The study was conducted at a commercial farm located near Buckeye, AZ. The experimental design was a randomized complete block with three replications. The treatments included 10" row spacings that were harvested with a finger stripper, 30" row spacings harvested with a brush stripper, and 30" row spacings harvested with a spindle picker. Plant growth and development was not affected by row spacing throughout the growing season. No significant difference was observed for lint yield however, gin turnout was slightly lower for stripper harvested treatments. Fiber quality measurements were similar for both row spacing with the exception of fiber micronaire which was lower in stripper harvested treatments. Bark was a major problem with stripper harvested treatments with at least 92% of bales receiving a discount compared with 36% of spindle harvested bales.
    • Short Staple Variety Trial in Virden, NM, 2000

      Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Twelve varieties were tested including three New Mexico Acalas and one Acala from Buttonwillow Research in California, three roundup ready varieties, a buctril resistant variety, a Bollgard variety and three other varieties. The highest yielding variety in the trial was FM 989 with a yield of 1046 pounds of lint per acre. It was also the highest yielding variety in the Cochise County trial the past two years, but had not been grown in Hidalgo or Greenlee Counties before. BW 9802, a variety from Buttonwillow Research in California, came in a close second. Interesting HVI data are also included in this report.
    • Mortality and Development Effects of Transgenic Cotton on Pink Bollworm Larvae

      Henneberry, T. J.; Forlow Jech, L.; de la Torre, T.; Silvertooth, Jeff; USDA-ARS, PWA, Western Cotton Research Laboratory, Phoenix, AZ 85040-8803 (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Pink bollworm (PBW), Pectinophora gossypiella (Saunders), larval mortality after different times of confinement on NuCOTN 33B® (Bt) cotton bolls were compared with larval mortality on Delta and Pineland 5415 cotton bolls as controls. We also compared larval mortality on different age cotton fruiting forms and determined the Bt susceptibility of different age PBW larvae. Infesting Bt bolls with PBW eggs that hatched within 24 h resulted in 92% larval mortality after 48 h and 100% mortality in 4 days or longer. There were no differences between cultivars in numbers of larval entrances holes into bolls. Generally, days to pupation for both males and females were longer on Bt bolls compared with non-Bt cotton. There were no significant mortality differences for larvae feeding on Bt fruiting forms of different ages ranging from one-half grown flower buds to 40-day old immature green bolls.
    • Upland Cotton Regional Variety Trial, 2000

      Hart, G.; Moser, H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Each year the University of Arizona conducts upland cotton variety tests to evaluate the performance of a diverse set of experimental and commercial varieties in Arizona. One such program is the Regional Variety Test (RVT). In 2000, we evaluated a total of 61 varieties at one or more locations in Arizona. These varieties were submitted to us for testing by 13 private seed companies and three public breeding programs. This report presents the results of the trials conducted at Maricopa, Marana, Safford and Yuma.
    • 2000 Low Desert Upland Cotton Advanced Strains Testing Program

      Husman, S.; Moser, H.; Wegener, R.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Upland cotton advanced strains and commercial check comparison varieties were evaluated in replicated field studies at four locations in 2000. The test sites include Yuma, AZ., Buckeye, AZ., Maricopa, AZ., and Safford, AZ.. Nine seed companies submitted a maximum of five advanced strains entries per location. Three commercial check varieties were used at each site for comparison purposes and included DP 5415, SG 125, and STV 474.
    • Short Staple Variety Trials in Cochise County, 2000

      Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Twelve varieties were tested including three New Mexico Acalas and one Acala from Buttonwillow Research in California, three roundup Ready varieties, a buctril resistant variety, a Bollgard variety and three other varieties. The highest yielding variety in the trial was 1517-99, with FiberMax 989, 1517-95 and SureGrow 521RR following in yield. Yields were considerably lower than seen in the previous year’s study (1). Several Roundup Ready varieties were included in this study. Plant mapping data and HVI data are also included in this report.
    • Cost-Effective Lygus Managment in Arizona Cotton

      Ellsworth, Peter C.; Barkley, Virginia; Silvertooth, Jeff; University of Arizona, Maricopa, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Timing sprays for maximum return on investment requires sampling and counting both Lygus adults and nymphs in a minimum of 100 sweeps. Once at least 15 total Lygus and 4 nymphs per 100 sweeps are detected, sprays for Lygus should be made. This '15/4' regime should protect yields, moderate spray frequency and costs, and maximize profit. Economic thresholds are impacted by the prevailing economic conditions such as lint value and costs of control; however in this case, the relationship that maximizes returns was not changed when varying these parameters well beyond market standards. A key finding of these studies is that aside from profits, yields plateau prior to the more aggressive treatment regimes. This phenomenon, where more protective approaches result in yield reductions, occurred in all three years of study (1997, 1999, 2000). This signals the importance of optimizing inputs so that sprays are made only when indicated by sampling and once the 15/4 level is reached, but no sooner. More aggressive approaches by definition cost more money to maintain, but also have some probability of lowering yields while risking secondary pest outbreaks. The specific mechanism for this yield decline is unknown at this time. At the other end of the spectrum, delaying action beyond the 15/8 action threshold risks economic yield loss and reductions in quality, especially color grade and micronaire. While this work definitively establishes the relative importance of Lygus nymphs to yield loss and to the need for action, the conditions under which these tests were carried out are limited to in-season infestations of Lygus. Further work is necessary to better quantify change in the action levels according to plant phenology and other plant-based factors (e.g., plant population, fruit retention, plantwater status, etc.). Early season infestations may respond differently to the action levels proposed, and it is expected that later season populations of Lygus pose far less damage potential when square populations and retention are very low.
    • Sustaining Arizona's Fragile Success in Whitefly Resistance Management

      Li, Andrew Y.-S.; Dennehy, Timothy J.; Li, Sarah X.-H.; Wigert, Monika E.; Zaborac, Marci; Nichols, R. L.; Silvertooth, Jeff; University of Arizona, Tucson, AZ; Cotton Incorporated, Cary, North Carolina (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      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.