• 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.
    • Relative Susceptibility of Whiteflies to Danital® + Orthone® Over a 5-year Period

      Castle, S. J.; Ellsworth, P. C.; Prabhaker, N.; Toscano, N. C.; Henneberry, T. J.; Silvertooth, Jeff; USDA-ARS Western Cotton Research Laboratory, Phoenix; The University of Arizona, Department of Entomology & Maricopa Agricultural Center; University of California, Riverside, Department of Entomology (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      As part of a program to assess differences in susceptibility to insecticides among regional populations of Bemisia tabaci, insecticide resistance monitoring was carried out at the Maricopa Agricultural Center from fall, 1995 through 1999. Monitoring efforts were concentrated on Danitol®+Orthene® following reports of control problems and documentation of resistance to this mixture in 1995. We were interested in the longer-term dynamics of resistance in light of radically altered treatment regimens beginning with the use of IGRs in 1996. Although the frequency of susceptible individuals to Danitol+Orthene tended to increase in the later years, highly resistant individuals were still present 5 years after the resistance episode of 1995. Whitefly adults collected from various insecticide treatment plots other than Danitol+Orthene were generally uniform in their responses from the time of initial whitefly infestation until defoliation. However, a dramatic shift in susceptibility occurred following a single application of Danitol+Orthene in 1997 and 1999. The increased frequency of resistant individuals following treatment suggests that any large scale return to the use of Danitol+Orthene could rapidly select for proportionally higher numbers of resistant whiteflies and perhaps reduced control in cotton fields.
    • 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.
    • 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 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.
    • 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.
    • 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.
    • Silverleaf Whitefly Studies: Effects of Trichome Density and Leaf Shape

      Chu, C. C.; Natwick, E. T.; Henneberry, T. J.; Nelson, D. R.; Buckner, J. S.; Freeman, T. P.; Silvertooth, Jeff; USDA, ARS, WCRL, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      We examined nine upland cotton cultivars in 2000 to determine silverleaf whitefly (SLW)-cotton leaf trichome relationships. The hairy leaf cultivar Stoneville 474 had significantly higher numbers of SLW eggs, nymphs and adults compared to eight other smooth leaf cotton cultivars. The top young leaves on main stem terminals had fewer SLW eggs, nymphs and adults, but higher numbers of trichomes compared with older leaves. Among the eight smooth leaf cultivars, the four okra leaf cultivars as a group had fewer SLW eggs, nymphs and adults compared with the four normal leaf cultivars.
    • Honeydew Production by Sweetpotato Whitefly Adults and Nymphs

      Henneberry, T. J.; Forlow Jech, L.; de la Torre, T.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory Phoenix, AZ 85040-8803 (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      We determined honeydew production by male and female sweetpotato whiteflies and the effects of temperature on honeydew production of each sex. We also determined honeydew production by each nymphal instar. Overall, adult SPW produced more honeydew than nymphs. Adult females produced more honeydew than males. The relative differences between honeydew production for males and females and between amounts adults produced compared with nymphs were consistent. However, honeydew production by adult and nymph individuals was subject to large degrees of variation.
    • 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.
    • Planting Date Effects Crop Growth and Yield of Several Varieties of Cotton, Marana 2000

      Silvertooth, J. C.; Galadima, A.; Norton, E. R.; Moser, H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A field study was conducted in 2000 at the University of Arizona Marana Agricultural Center (1,974 ft. elevation) to evaluate the effects of three planting dates on yield and crop development of 13 varieties of upland cotton. Planting dates included 4 April, 21 April, and 9 May. The associated heat units accumulated since 1 January were 617, 877, and 1203 respectively (using 86/55 °F maximum/minimum thresholds respectively). Results indicate that there was a significant interaction between planting date and variety. Overall, lint yields significantly declined with later planting dates and significantly varied among varieties within each planting date.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.