• Telone II® and Temik® Efficacy on Rootknot Nematodes in Cotton

      Husman, S.; McClure, M.; Lambeth, J.; Dennehy, T.; Deeter, B.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Field studies were conducted at four western Maricopa County commercial sites in 1994 to determine whether Temik 15G® would suppress rootknot nematode at low to moderate populations. Three of the experiments were on Upland D +PL 5415 with the fourth on Pima S-6. Sites were chosen based on pre- season sampling with individual field populations ranging from 0.005 (low) - 3.6 (high) rootknot nematode juveniles per cubic centimeter (cc) of soil volume. Each study consisted of four treatments with six replications. The following treatments were used at all test sites: (1) Untreated check, (2) 5 lbs. Temik 15G at planting, (3) 5 lbs. Temik 15G at planting, 15 lbs. Temik 15G sidedressed at pinhead square, (4) 5 gal. Telone 11® pre-plant. Sampling for thrips and lygus was conducted at all test sites to provide insight regarding yield effects resulting from control of insect versus those due to suppression of nematode. There were no significant yield differences between the untreated check and either Temik treatment. However, significant yield increases were measured with Telone versus all treatments at all locations. Insect pressures were minimal in all cases. Temik 15G did not suppress nematode damage at any population level.
    • Timing Initial Post-plant Irrigation Based upon Plant-Water Status

      Steger, A. J.; Silvertooth, J. C.; Brown, P. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      A two year study was conducted to determine the optimum timing of the initial post plant irrigation using leaf water potential (LWP) measurements. A short - season Upland cotton (Gossvpium hirsutum L.), variety DPL 20, was planted on 19 April 1993 and 15 April 1994 at the Marana Agricultural Center on a Pima clay loam (Typic Torrifluvent) soil. Treatments, designated Tl , 72, and T3, were such that the initial post plant irrigation would be applied when the midday LWP of the uppermost, fully- developed leaf exposed to full sunlight measured -15, -19, and -23 bars, respectively. All treatments received the same irrigation regime following the initial post plant irrigation. Basic plant measurements, including plant height, mainstem node number, fruit retention, number of nodes above the uppermost white bloom, fresh bloom count within a 166 -ft1 area, and percent canopy cover, were taken weekly from each plot. Soil -water data was collected at 10 inch depth increments, to a depth of 60 in. , from access tubes located in each experimental unit. Yields were 1112, 1095, and 977 lbs lint/acre in 1993 and 1082, 1035, and 964 lbs lint /acre in 1994 for T1, 72, and T3, respectively. Yields were reduced when the midday LWP was allowed to fall below -19 bars, however, reduction was significant (P 5 0.05) only in 1993. At the time of the initial post plant irrigation for each treatment, approximately 83, 62, and 32 % of the total plant available water was present in the upper 60 in. of the soil profile for Ti, 72, and T3, respectively.
    • Upland Advance Strains Cotton Variety Test at the Maricopa Agricultural Center

      Hart, G. L.; Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Thirty -six upland cotton advance strains were grown in a replicated trial at the Maricopa Agricultural Center. Lint yield, boll size, lint percent, plant population and fiber property data are presented in this report.
    • Upland Cotton Water Stress Sensitivity by Maturity Class and Suggesting Management Strategy

      Husman, S.; Wegener, R.; Brown, P.; Martin, E.; Johnson, K.; Schnakenberg, L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Lint yield response to differing irrigation treatments based on maximum allowable soil moisture depletions was tested in an indeterminate (D +PL 5816) and a determinate variety (D+PL 5415) selection. The Arizona Meteorological Weather Network (AzMet) was used to summate evapotranspiration demands with irrigations triggered at 35 (wet), 50 (med), and 65 % (dry) maximum allowable soil moisture depletion levels. Soil water holding capacity was gravimetrically measured to a depth of four feet on one foot increments. The study consisted of three treatments replicated four times utilizing a complete block split plot design. When the allowable depletion level was attained, the water volume necessary to refill the effective root zone was delivered. This was accomplished by manipulating irrigation set times and flow rates. Irrigation volumes were 66.7, 57.2, and 46.9 acre - inches for the wet, medium, and dry treatments respectively. Lint yields were significantly reduced when the maximum allowable soil moisture depletion exceeded 50% in the determinate variety selection while there were no significant lint yield differences in any of the irrigation treatments with the more indeterminate variety. Water stress sensitivity is increased with the determinate variety while the indeterminate variety is more forgiving. With variety selection shifts in the Central Arizona desert towards a reduced season approach and utilization of more determinate varieties, water management strategy should be modified to minimize or eliminate any water stress during the flowering period. The AzMet weather network information offers cost effective (free) and reliable water use information. The system can be used to assist with irrigation scheduling if a producer is willing to attempt to characterize differing soil water holding capacities on the farm and manage accordingly.
    • Upland Regional Cotton Variety Test at the Maricopa Agricultural Center, 1994

      Hart, G.; Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Twenty-seven upland cotton varieties were grown in a replicated test 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 data are presented in this report.
    • The Use of Fungi to Prevent Aflatoxin Contamination of Cottonseed in the Yuma Valley

      Cotty, P. J.; Silvertooth, Jeff; USDA, ARS, Southern Regional Research Center, New Orleans, LA (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      A strain of Aspergillus flavus that does not produce aflatoxins was applied to soils planted with cotton at the Yuma Valley Agricultural Center in order to assess strain ability to competitively exclude aflatoxin producing strains during cotton boll infection and thereby prevent aflatoxin contamination of cottonseed. In both 1989 and 1990, the atoxigenic strain displaced other infecting strains during cotton boll development. Displacement was associated with significant reductions (75% to 82% in 1989, and 99% in 1990) in the quantity of aflatoxins contaminating the crop at maturity. Although frequency of infected locules differed between years, in both years displacement occurred without increases in the amount of developing boll infection. Currently, an Experimental Use Permit is being sought from the EPA for tests on commercial acreage