• 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.
    • 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.
    • Bollgard® and Bollgard II® Efficacy in Near Isogenic Lines of 'DP50' Upland Cotton in Arizona

      Marchosky, Ruben; Ellsworth, Peter C.; Moser, Hal; Henneberry, T. J.; Silvertooth, Jeff; Department of Entomology, University of Arizona, Maricopa, AZ; USDA-ARS, WCRL, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      The Cry1Ac gene (Bollgard®) is available in cotton either alone ('B') or in combination (Bollgard II®) with a second gene, Cry2Ab ('X'). We evaluated these two different transgenes, separately and together, in near isogenic lines of the upland cotton variety ‘DP50’. DP50B was previously transformed with the Cry2Ab gene to give rise to the experimental line 985BX which was then back-crossed to DP50 to produce near isogenic single gene variants, 985B and 985X. The lepidopteran target was pink bollworm (PBW), Pectinophora gossypiella (Saunders), which was evaluated in two field studies through a series of samples from artificially and naturally-infested bolls. In one study (NTO), three cotton lines (DP50, DP50B, 985BX) were evaluated under three spray regimes. In the second study (Isoline), five near isogenic lines (DP50, DP50B, 985B, 985X, 985BX) were evaluated under two spray regimes: fully sprayed and lepidopteran unsprayed. In lines containing only one transgene, Cry1Ac or Cry2Ab, bolls had consistently fewer PBWs than the non-Bt variety. Very few PBWs developed into large (3rd instar) larvae in these Bt varieties. The majority (NTO: 83%; Isoline: 94%) of PBWs recovered were dead first instar larvae. Less than 5% of the DP50B bolls in the NTO study were infested with feral large (≥3rd instar) larvae, and large larvae were present in less than 2% of naturally-infested bolls of single-gene lines in the Isoline study. PBW age and mortality distributions confirmed that the single transgenes were effective in stopping PBW development and killing young instars. Cry2Ab displayed a broader spectrum of efficacy as it was significantly more effective against citrus peelminer (Marmara spp.), an incidental lepidopteran present in high densities in the tests. The two-gene (Cry1Ac + Cry2Ab) line showed better (at least 10-fold) efficacy than the single-gene lines against PBW large larvae infestation. The PBW age distributions found in this variety consisted almost entirely (98%) of dead first instar larvae. Less than 0.6% of the bolls of the two-gene variety in the NTO study were infested with large (≥3rd instar) larvae, and there was no infestation by large larvae in any of the naturally-infested bolls in the Isoline study. Yields and other agronomic parameters of the two-gene and single-gene varieties were superior or similar to the null parent. Second pick yields of all Bt varieties were significantly higher than the recurrent parent non-Bt line, suggesting a high degree of efficacy against typically high PBW densities during the late season. Cotton lines with transgenes (Cry1Ac & Cry2Ab) separately and combined demonstrated a high degree of efficacy and agronomic performance for usage in Arizona against PBW. The ramifications of isogenic comparisons of PBW incidence on efficacy and resistance monitoring are discussed.
    • Soil and Plant Recovery of Labeled Fertilizer Nitrogen in Irrigated Cotton

      Silvertooth, J. C.; Navarro, J. C.; Norton, E. R.; Galadima, A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Proper timing of fertilizer N applications in relation to crop uptake can serve to improve fertilizer efficiency in irrigated cotton. Earlier research has identified an optimum application window extending from the formation of first pinhead squares to peak bloom, which corresponds well with maximum crop uptake and utilization. Field experiments were conducted at the University of Arizona Marana Agricultural Center (Grabe clay loam soil) utilizing sidedress applications of ammonium sulfate with 5-atom % 15-N at pinhead square, early bloom, and peak bloom at a rate of 56 kg N/ha. The objective was to compare relative efficiencies in terms of fertilizer N uptake and recovery among these three times of application. Results indicate that all treatments averaged approximately 80% total fertilizer N recovery. Of the fertilizer N that was recovered, approximately 40 % was taken up by the plants and 60 % recovered in the soil, primarily in the top 60 cm of the soil profile.
    • 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.
    • Agronomic and Economic Evaluation of Ultra Narrow Row Cotton Production in Arizona 1999-2000

      Husman, S. H.; McCloskey, W. B.; Teegerstrom, T.; Clay, P. A.; Wegener, R. J.; Silvertooth, Jeff; University of Arizona Cooperative Extension, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Ultra Narrow Row (UNR) and conventional (CNV) cotton production systems were compared with respect to agronomic practices, yield, fiber quality, and production costs in experiments conducted in 1999 and 2000 in central Arizona. Cotton rows were 10 and 40 inches apart in the UNR and CNV systems, respectively. In 1999, the average lint yield in the UNR system, 1334 lb/A, was significantly greater than the 1213 lb/A yield of the CNV system. Similar results were obtained in 2000 with yields of 1472 and 1439 lb/A for the UNR and CNV systems, respectively. Fiber grades of both systems were comparable with most bales receiving a grade of 21 in 1999. The average bale grades in 2000 were 11 and 21 in the UNR and CNV systems, respectively. The quality of the fiber produced in both systems was also comparable with staple and strength measurements meeting base standards in both years. However, there was a consistent difference between the UNR and CNV systems in both years with respect to micronaire. Micronaire averaged 4.5 and 4.0 in the UNR system in 1999 and 2000, respectively, and 5.0 and 4.9 in the CNV system in 1999 and 2000, respectively. Variable growing costs were $607 and $446 for the UNR system in 1999 and 2000, respectively, and $660 and $519 for the CNV system in 1999 and 2000, respectively. Harvest and post-harvest variable costs were $234 and $209 in the UNR system in 1999 and 2000, respectively, and $217 and $224 in the CNV system in 1999 and 2000, respectively. The economic data indicated that the UNR system reduced production costs and increased profitability without sacrificing lint yield or quality. However, these experiments also indicated that many production challenges such as planting and obtaining adequate plant populations, managing plant height control, and weed control need further study.
    • Insecticide Evaluation Studies, Safford Agricultural Center, 1999-2000

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Three studies were conducted over the two year period to explore the effectiveness of using pyrethroid insecticides only vs. rotating insecticide chemistries between the pyrethroids and organophosphates on both long and short staple cotton varieties. These same treatments were also evaluated over Bt and non-Bt varieties. In the worst case scenario, where weather conditions prevented timely application of insecticides and effectiveness of insecticides applied, long staple cotton yielded around 1/3 bale per acre after six insecticide applications. Within 200 feet of this experiment, during the same cropping season, with the same insecticides applied, DP 90B (a Bt variety) produced 3 bales per acre. Details of these studies are contained in this report.
    • Evaluation of a Drip Vs. Furrow Irrigated Cotton Production System

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      A newly installed subsurface drip system was compared to a conventional furrow-irrigated cotton production system in the Marana Valley in 2000. Regular measurements included soil moisture, flower tagging, general plant growth and development measurements, and lint yield. Results indicate that an increase in lint yield of approximately 250 lbs. lint/acre was obtained under the drip irrigation system. Approximately 1/3 less irrigation water was used under the drip irrigation system. Pounds of lint produced per acre-inch of water applied provide the most dramatic results. In the furrow-irrigated system approximately 25 lbs. of lint was produced per inch of water applied while the drip system ranged from 70-80.
    • Effects of High Frequency Irrigation on Irrigation Uniformity III

      Martin, E. C.; Laine, G.; Sheedy, M.; Silvertooth, Jeff; University of Arizona, Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Data was collected for a third season to determine the effects of high frequency irrigation on irrigation uniformity in cotton production. The past two seasons indicated that high frequency irrigation worked better on sandier soils than soils containing high clay contents. Although no significant differences were found, higher yields were obtained on a site with a relatively high sand content. A field located at the Maricopa Agricultural Center was split into two treatments. Treatment 1 was irrigated at approximately 35% depletion of available water in the plant rootzone. Treatment 2 was irrigated at approximately 50% depletion in the crop rootzone. Although the yield data from Treatment 1 was higher on the average, statistically, there was no difference between the two treatments.
    • Cotton Aphid Biology and Honydew Production

      Henneberry, T. J.; Forlow Jech, L.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Cotton aphid, Aphis gossypii Glover, fecundity, nymph development and honeydew production were studied in the laboratory. Apterous adult females produced an average of 1.7 nymphs per day and the nymphs (four instars) developed to adults in an average of 4.1 days at 26.7° C in the laboratory. Average longevity of adults was 16.1 days. More honeydew drops were produced by one-day old nymphs than three- or four-day old nymphs. Numbers of honeydew drops produced on a day to day basis were highly variable and did not show a distinct pattern of production. More honeydew drops, sugars and progeny were produced by adults at 26.7° C compared with 15.6 or 32.2° C. Increasing times of exposure of clean cotton lint to aphids and the resulting increasing amounts of honeydew sugars under laboratory and field conditions were significantly related to increasing cotton lint stickiness as measured with a thermodetector.
    • Soil Amendment Study on Long and Short Staple Cotton, Safford Agriculture Center, 2000

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2001)
      Two soil amendments, Agriblend Plus and Superfloc A-836, were applied to cotton beds prior to planting at rates of 5, 10, 15 and 20 pounds per acre, incorporated and planted to short staple (DP 655BR) or long staple (HTO) cotton. The experimental plots were fertilized, irrigated and managed in a manner to produce optimal cotton yields. No statistically significant yield increases were seen from any of the treatments, even though a few interesting trends were observed. The report contains observations on plant mapping and lint quality data, in addition to yield data.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.