• Agronomic Evaluations of New Transgenic and Non Transgenic Cotton Varieties in La Paz and Mohave Counties

      Knowles, Tim C.; Wakimoto, Del; Sprawls, Greg; Hurtado, Greg; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      In 1996 transgenic Bt cotton was first grown on a commercial level in Arizona. In 1997 transgenic Roundup and Buctril herbicide resistant cotton varieties were introduced and grown on commercially in Arizona. Furthermore, in 1997, four new heat tolerant non- transgenic cotton varieties for commercial release in 1998 were available for University field tests. Prior to 1997, the agronomic characteristics of these new cotton varieties had not been evaluated inside by side replicated field comparisons beyond the level of the developing companies. Field tests were conducted in La Paz and Mohave Counties in 1997 examining agronomic characteristics of new transgenic Bt ( Deltapine 5415 vs. Deltapine 32 B and 33B) and herbicide resistant (Paymaster 1220 BGRR vs. 1244 BGRR and Stoneville 474 vs. BXN 47) and non transgenic heat tolerant (SureGrow 125 vs. 180 and 821, Stoneville 474 vs. 468, and Germain's GC 9230) cotton varieties.
    • Defoliation Tests with Ginstar at the Maricopa Agricultural Center in 1997

      Nelson, John M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Defoliation tests were conducted on Upland and Pima cotton at the Maricopa Agricultural Center to evaluate rates of Ginstar, tank mixes of Ginstar with other defoliants and Ginstar used as a preconditioner. The cotton used in these tests was generally difficult to defoliate, probably because of an excessive supply of nitrogen and cool temperatures in October and November. In early October, only the Ginstar + Def treatment gave good defoliation of upland while all treatments gave good defoliation of Pima cotton. In late October tests, temperatures were cool and only Ginstar + Def and Ginstar followed by Ginstar treatments gave effective defoliation in 14 days. In October and November tests, Ginstar used as a preconditioner was effective in helping to defoliate cotton under, cool weather conditions.
    • Nitrogen Management Experiments for Upland and Pima Cotton, 1997

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Two field experiments were conducted in Arizona in 1997 at two locations (Maricopa and Marana). The Maricopa experiment has been conducted for eight consecutive seasons, the Marana site was initiated in 1994. The purposes of the experiments were to validate and refine nitrogen (N) fertilization recommendations for both Upland and Pima 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.
    • Effects of Entomopathogentic Nematodes on Pink Bollworm Mortality

      Henneberry, T. J.; Forlow Jech, L.; Burke, R. A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Steinernema riobravis Cabanillas, Poinar & Raulston infected pink bollworm Pectinophora gossypiella (Saunders), larvae over a temperature range of 15.6 - 38.0° C. Temperatures of 32.2° C and higher and exposure for 48 h or more often resulted in decreased numbers of nematode killed larvae with living nematodes and increased numbers of dead larvae with dead or no nematodes.
    • 1997 Season Update on Resistance of Arizona Whiteflies to Synergized Pyrethroid and Select Non-Pyrethroid Insecticides

      Dennehy, Timothy J.; Williams, Livey III; Li, Xiaohua; Wigert, Monika; Silvertooth, Jeff; Department of Entomology, The University of Arizona; Extension Arthropod Resistance Management Laboratory, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A whitefly resistance crisis in Arizona in 1995 prompted the development of a resistance management strategy in 1996 that recommended maximal once per season use of two insect growth regulators, pyriproxyfen (Knack®) and buprofezin (Applaud®), and limited and delayed use of synergized pyrethroid insecticides in cotton. Statewide monitoring of whitefly resistance has shown that implementation of this strategy has substantially reduced whitefly resistance to the synergized pyrethroids and has also resulted in increased susceptibility to key non pyrethroid insecticides. Having benefited from two years of success with this strategy, the Arizona cotton industry now faces the question of whether it can be sustained as pyriproxyfen and buprofezin gain additional registrations for use against whiteflies in vegetables, melons and glasshouse crops.
    • Late Season Pink Bollworm Pressure in the Top Crop of Bt and Non-Bt Cotton

      Knowles, Tim C.; Dennehy, Tim J.; Rovey, Albert; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Green bolls (100/field) were sampled from the uppermost internodes within adjacent fields of Bt (Deltapine 33B) and non-Bt (Hyperformer HS 44) cotton experiencing severe pink bollworm pressure late in the growing season. Average top crop lint yield reductions ranging from 30 to 70% were observed in the uppermost bolls of the non-Bt cotton variety. Average top crop lint yield reductions ranging from 0 to 40% were observed in the uppermost bolls of the transgenic Bt cotton variety.
    • Correlation between Early Season Insecticide Control of Pink Bollworm and Other Pests and Subsequent Whitefly Applications near Gila Bend, AZ, 1997

      Jech, L. E.; Husman, S. H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Cotton pesticide application histories in the Gila Basin were followed from 27 April through 20 September. The main interest was the effect of early season applications to control pink bollworm, Pectinophora gossypiella, and other pests on subsequent whitefly applications. Categories explored include, transgenic and non transgenic cotton, planting dates, and location within the valley. Regression analysis shows a significant effect due to the early season control for either P. gossypiella, or other pests (P > 0.009) but lower for them together (P > 0.026). Early applications for either PBW or other pest resulted in increased application for whitefly.
    • Irrigation Efficiencies and Lint Yields of Upland Cotton Growth at the Maricopa Agricultural Center, 1997

      Sheedy, Mike; Watson, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A field trial was conducted at the Maricopa Agricultural Center to observe the effects of four irrigation efficiencies (65%, 75%, 85%, and 95%) on the lint yield produced from two upland cotton varieties (DP 5409 and SG 125). Nitrogen requirements for the crop were determined using pre- season soil samples and in season petiole samples in conjunction with crop monitoring data collected at weekly intervals. AZSCHED was used as a guide to the irrigation timing and amount of water applied during the season. This year there was a lint yield response to the different irrigation efficiencies, and a slight difference in yield between the two varieties. Lint yields were significantly lower in the 95% irrigation efficiency plots. Lint Yields ranged from 1448 # lint /acre (SG125 at 75%) to 1220 # lint/acre ( DP5409 at the 65% irrigation efficiency).
    • Date of Planting by Long Staple and Short Staple Variety Trial, Safford Agricultural Center, 1997

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Four varieties each of Long Staple and Short Staple cotton were tested over five and four dates of planting, respectively, in this study. The first date of planting for the Long Staple cotton was pushed up to the 18th of March because planting is now legal in Graham county as early as March 15th. The latest planting was May 13th. Cultivars of differing maturities were tested for both long and short staple cotton to determine their optimal planting time. Many agronomic and hvi values were evaluated to determine the effect of different planting dates
    • Evaluation of 1997 Late-Season Crop Conditions

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

      Hart, G. L.; Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Thirty four upland cotton varieties were grown at the Maricopa Agricultural Center as part of the national cotton variety testing program. Lint yield, boll size, lint percent, plant population and fiber property are presented in this paper.
    • Evaluation of Irrigation Termination Affects on Upland Cotton, 1997

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

      Knowles, Tim C.; Wakimoto, Vic; Wakimoto, Del; Keavy, Mike; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Transgenic Bt cotton varieties that are resistant to pink bollworm should sustain less feeding damage to bolls and cottonseed, compared to non-Bt varieties that are more susceptible to feeding damage by pink bollworm larvae. Prior to boll opening, the aflatoxin producing fungus Aspergillus flavus cannot penetrate undamaged cotton bolls. Thus resistance to pink bollworm could result in reduced aflatoxin contamination under high pink bollworm pressure. Cottonseed aflatoxin levels of Bt and non-Bt varieties were compared at various planting and harvest dates. Bt and non-Bt cotton varieties had similar cottonseed aflatoxin levels. Long season production systems favored high cottonseed aflatoxin levels, compared to short season production systems, regardles of the cotton variety grown.
    • Fungicide Treatment and Varietal Effects on Alternaria Leaf Spot of Pima Cotton

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

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

      Misaghi, I. J.; Heydari, A.; Zoki, K.; Silvertooth, Jeff; Department of Plant Pathology, University of Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      We conducted four field trials in April 1995 and 1996 in Arizona to compare the effectiveness of the following treatments to reduce cotton seedling damping-off incidence: 1) a soil drench of an isolate of the bacterium, Burkholderia cepacia (DI), recovered by us from cotton plants; 2) isolate D1 barley meal formulation; 3) Deny® seed treatment (a peat moss -based formulation of another isolate of B. cepacia, CCT Corp. Carlsbad, California); 4) Deny® soil drench; 5) Kodiak® seed treatment (a formulation of the bacterium, Bacillus subtilis, Gustafson Inc., Dallas, Texas); 6) a mixture of three fungicides Metalaxyl, Triadimenol, and Thiram seed treatment; and 7) a mixture of Metalaxyl, Triadimenol, Thiram, and Kodiak® seed treatment. Except for DI, the other products are being marketed for the control of cotton seedling damping-off Only DI soil drench and a mixture of the three fungicides seed treatment increased cotton stand significantly (P ≤ 0.05) in three of four field trials.
    • Comparison of the Two Methods for the Analysis of Petiole Nitrate Nitrogen Concentration in Irrigated Cotton

      Smith, J. H.; Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A study was conducted in Arizona in 1997 with the objective of analyzing the accuracy of a recently developed portable nitrate meter (Cardy meter) to effectively measure petiole nitrate - nitrogen (NO₃-N) in irrigated cotton (Gossvpium sue.). This task was accomplished by performing correlation and linear regression analyses on NO₃-N concentrations of cotton petiole sap, as measured by the Cardy meter, against the standard procedure NO₃-N analysis, as measured by an ion selective electrode (ISE). Results revealed that the NO₃-N concentrations of petiole sap were highly correlated with dried petiole NO₃-N (pearson correlation coefficient = 0.96, P < 0.0001). A regression equation with an r² = 0.92 was derived: Y = 9.96X - 1170.86, where X and Y are NO₃-N in petiole sap (ppm) and dried petioles (ppm), respectively. These results suggest that the sap analysis using the Cardy meter is a potentially valuable tool to monitor the in-season N status of irrigated cotton.
    • 1997 Cottonseed Variety and Treatment Evaluation

      Knowles, Tim C.; Wakimoto, Del; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Three upland cotton varieties (Deltapine 5415, Stoneville 474, and SureGrow 125) were subjected to three seed treatments (non or control, standard commercial triple treated, and standard commercial plus Prevail added to the hopper box at 1 lb product /100 lb cottonseed) to determine seed germination and vigor in a Mohave Valley field prone to Rhizoctonia infection of cotton seedlings.
    • Mathematical Models of Potassium Release Kinetics for Sonoran Desert Soils of Arizona

      Galadima, A.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      The objective of this study was to determine the potassium (K) release kinetics of clay samples from 10 agricultural representative soils of Arizona by successive extraction using Ca-saturated cation resin. A 1993 physical and chemical characterization of the soils revealed that all soils contain smectite-mica K bearing minerals. Four mathematical models (power function, Elovich, parabolic diffusion and first-order) were used to describe the nonexchangeable K release reaction involving 700-hr cumulative reaction time. Comparison of the models using the coefficient of determination (r²) and the standard error of the estimate (SE) indicated that the Elovich and the power function equations overall displayed the best fit. The first-order rate and for the most part, the parabolic diffusion equation did not describe the K release very well. The constants a and b for the Elovich and the power function equations, which represent the intercept and the release rate of the nonexchangeable K respectively, are at least in the order of magnitude as those found by others in several previous studies.
    • Side-dress Temik® Effects on Lint Yields

      Husman, Stephen H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Temik 15G was side-dressed at a rate of 7 lb./acre and 14 lb./acre and compared to an untreated check in 4 experiments in 1996 and 1997 in Buckeye, Az. Treatments were made just prior to early bloom. Lygus counts were taken using a sweep net on weekly intervals for four to six weeks post application. A net positive return on investment (ROI) ranging from $34.79/acre to $48.19/acre was realized in three of the four experiments with the seven lb./acre rate. One experiment resulted in a net economic loss of $24.84. A net positive ROI was experienced in two of the four experiments ranging from $23.31 to $50.11 using the fourteen lb./acre Temik rate. Two of the four experiments resulted in a net loss ranging from $28.28 to $93.27 using the fourteen lb./acre rate. It appears that lint yield increase responses are due in part to a plant response to Temik, not necessarily related to lygus density as evidenced in part by the lack of measured sweep count populations.