• 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.
    • 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.
    • 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.
    • 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.
    • Cotton IPM in Arizona: A Decade of Research, Implemention & Education

      Ellsworth, Peter C.; Jones, Jennifer S.; Silvertooth, Jeff; University of Arizona, Maricopa, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Cotton production in Arizona has been faced with major challenges in insect control during the past decade. These challenges have been met through IPM programs of research, implementation, and education. The decade began (1990) with an outbreak of our key lepidopteran pest, the pink bollworm. Growers sprayed for all pests more than 11 times at a cost of over $113 / A that year. The following years (1991–1995) saw the introduction of and devastation by a serious, quality-reducing insect, the sweetpotato or silverleaf whitefly. Growers sprayed up to 6.6 times (1995) at a cost of over $145 / A to combat this single insect pest. The cotton IPM program at the University of Arizona along with industry, grower, and USDA partners readied farmers for the introduction (1996) of two strategic sets of pest control technology, ‘Bt’ transgenic cotton and insect growth regulators (IGR). Through an aggressive educational campaign, growers learned about the safe, effective, and sustainable use of these technologies. As a result, cotton growers saw their average spray requirement plummet from 12.5 sprays at $217 / A (1995) to an historic low of 1.91 sprays at $37 / A (1999). Now new threats from an old pest, Lygus bugs, pose serious challenges to these staggering advances in cotton IPM. This paper highlights the key advances made in research, implementation, and education during this volatile decade. Furthermore, we conclude with one example how systematic, large-scale, and long-term research can provide insight into the role that new technology and the knowledge to use it properly have on cotton grower and industry success.
    • 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.
    • Evaluation of a Calcium-Based Soil Conditioner in Irrigated Cotton

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A two site evaluation of a calcium (Ca²⁺)-based soil conditioner was conducted during the 1999 cotton season. The two locations included one at the Maricopa Agricultural Center (MAC) in Maricopa, AZ and the other was on a grower-cooperator field in Tacna, AZ. Both studies involved the use of CN-9, a Ca-nitrate solution with 9% nitrogen and 11% Ca. At MAC theCN-9 solution was sprayed over the seedbed post planting but prior to the first water-up irrigation. At the Tacna site CN-9 was applied in a sidedress application at planting. Routine plant measurements were taken throughout the duration of both studies and lint yield estimates were made at each location at the end of the season. No significant differences due to the application of CN-9 were detected in any data collected.
    • Evaluation of Potassium and Phosphorus Fertility in Arizona Soils

      Silvertooth, J. C.; Norton, E. R.; Galadima, A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Two field experiments were conducted during the 2000 growing season to address fertility recommendations for fertilizer phosphorus (P) and potassium (K). A K fertility study was conducted near Tonopah, AZ consisting of two treatments, an untreated control and a treatment receiving a total of 20 gallons of K-Sul/acre. No significant differences were observed in leaf blade K concentrations between treatments. Plant growth and development estimates revealed that fruit retention (FR) levels remained consistently higher in the untreated control versus the treated plots. A second study involved treatments consisting of both P and K fertilizers was conducted near Cibola, AZ. Four treatments in this experiment included an untreated control plus treatments of 11-52-0, 0-0-60, and 4-17-40 at 100, 200, and 300 lbs. fertilizer/acre respectively. Plant growth and development estimates were similar among treatments during the season. At the end of the season the untreated control had a slightly higher FR level than the other treatments, which also produced a significantly higher yield. No other differences in yield among the fertilized treatments were observed.
    • Nitrogen Management Experiments For Upland and Pima Cotton, 2000

      Silvertooth, J. C.; Norton, E. R.; Galadima, A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Two field experiments were conducted in Arizona in 2000 at two locations (Maricopa and Marana). The Maricopa experiment has been conducted for nine consecutive seasons; the Marana site was initiated in 1994. The purposes of the experiments were to validate and refine nitrogen (N) fertilization recommendations for Upland cotton. The experiments each utilized N management tools such as pre-season soil tests for NO₃⁻-N, in-season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. At each location, treatments varied from a conservative to a more aggressive approach of N management. Results at each location revealed a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis as a response to the N fertilization regimes used. The higher, more aggressive, N application regimes did not benefit yields at any location. In 2000, fruit retention levels were good and crop vigor was not excessive. The more conservative, feedback approach to N management provided optimum yields at both locations.
    • Evaluation of Crop Management Effects on Fiber Micronaire, 2000

      Silvertooth, J. C.; Galadima, A.; Norton, E. R.; Tronstad, R.; 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 management can impact fiber micronaire. Approximately 250 cases were identified in cotton production areas in Arizona ranging from the lower Colorado River Valley to near 2,000 ft. elevation with grower cooperators in the 2000 season. Field records were developed for each field by use of the University of Arizona Cotton Monitoring System (UA-CMS) for points such as variety, planting date, fertility management, irrigation schedules, irrigation termination, defoliation, etc. Routine plant measurements were conducted to monitor crop growth and development and to identify fruiting patterns and retention through the season. As the crop has approached cutout and the lower bolls began to open, open boll samples have been collected from the lowest four, first position bolls (theoretically the bolls with the highest micronaire potential on the plant) from 10 plants, ginned, and the fiber analyzed for micronaire (low 4). From that point forward, total boll counts per unit area and percent open boll measurements are being made on 14-day intervals until the crop is defoliated. Following defoliation, final plant maps were performed. Relationships among low 4 samples micronaire, irrigation termination (IT), defoliation, and final crop micronaire were analyzed.
    • Summary of Nitrogen Management Experiments in Irrigated Cotton

      Silvertooth, J. C.; Norton, E. J.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A series of nitrogen management experiments have been conducted over the past 11 years around the state to develop and refine fertilizer nitrogen (N) recommendations for irrigated desert cotton production. Stability analysis was used to summarize the data and to determine which of the four treatment regimes is most stable over a range of environments. Results indicate that the feedback treatment (treatment 3) was the most stable treatment for both Upland and Pima cottons and provided the best probability for a higher yield under high yielding environments. The untreated control treatment (treatment 1) was the least stable over a wide range of environments. These results further validate the ‘feedback’ approach to management of fertilizer N.
    • 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.
    • Pest and Pesticide Usage Patterns in Arizona Cotton: Final 2000 Date

      Agnew, G. E.; Baker, P. B.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Arizona's pesticide use reporting (PUR) database is used to track and quantify the general decline in pesticide use in the state. A full summary of the official 2000 growing season pesticide usage is included. The database also enables tracking of changing usage patterns. For two years, target pest information has been included in the Arizona PUR database. Limitations in the PUR database are discussed. The reporting coverage shortfall for insecticide reports in the PUR database is estimated and found to be reasonable relative to sample based approaches to pesticide use reporting.
    • 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.
    • 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.
    • 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.
    • 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.
    • Arizona's Multi-agency Resistance Management Program for Bt Cotton: Sustaining the Susceptibility of Pink Bollworm

      Sims, Maria A.; Dennehy, Timothy J.; Patin, Amanda; Carrière, Yves; Liu, Yong-Biao; Tabashnik, Bruce; Antilla, Larry; Whitlow, Mike; Silvertooth, Jeff; Department of Entomology, The University of Arizona, Tucson, AZ; et al. (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Bt cotton has been used in Arizona since 1996 with exceptionally positive results in terms of economic returns to growers and reductions in insecticide use in cotton. Yet, the isolation of pink bollworm highly resistant to Bt cotton from collections made in Arizona in 1997 demonstrated the seriousness of the threat that resistance poses to transgenic Bt technology. For this reason unparalleled measures have been taken to detect and manage resistance of pink bollworm to Bt cotton in Arizona. This paper presents results of statewide monitoring of pink bollworm susceptibility to the Bt toxin, Cry1Ac, conducted from 1997 to 1999. Mean susceptibility of Arizona pink bollworm to Cry1Ac increased from 1997 to 1999. Mean corrected mortality in 1μg/ml Cry1Ac assays was 52.3% in 1997, 90.6% in 1998, and 97.9% in 1999. Mean corrected mortality in bioassays of 10 μg/ml was 94.5% in 1997, 99.8% in 1998, and 100% in 1999. Selection with Cry1Ac in the laboratory has produced from 1997 field collections a strain possessing 200 to 900-fold resistance to Cry1Ac. This resistant strain is capable of surviving on Bt cotton. We provide an overview of other components of the multi-agency collaboration to sustain efficacy of Bt cotton in Arizona. These include: 1) evaluation of the field performance of Bt cotton; 2) mapping and analysis of use of Bt and non-Bt cotton and compliance with refuge requirements; 3) effectiveness of internal versus external refuges and movement of pink bollworm moths from refuges; and 4) activities of the Arizona Bt Cotton Working Group to formulate and implement effective resistance management strategies.