• The Arizona Cotton Advisory Program

      Brown, P.; Russell, B.; Silvertooth, J.; Ellsworth, P.; Stedman, S.; Thacker, G.; Hood, L.; Husman, S.; Cluff, R.; Howell, D.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Arizona Cooperative Extension generates and distributes weather -based Planting Date and Cotton Development Advisories for 10 cotton production areas (Marana, Litchfield Pk, Pinal Co., Parker, Safford, Yuma Valley, Dateland and Aguila). Planting Date Advisories are distributed from mid - February through the end of April and stress 1) planting all (particularly full season varieties) cotton varieties according to heat unit accumulations rather than calendar date and 2) the importance of soil temperature to good germination. Cotton Development Advisories are distributed from early May through mid -September and provide updates on crop developmen4 insects, weather and agronomy to growers. The Cotton Advisory Program will continue in 1993 and growers may obtain the advisories by mail (far only in Yuma County only) from the local county extension office or by computer from the AZMET computer bulletin board.
    • Arizona Upland Cotton Variety Testing Program

      Silvertooth, J.; Hood, L.; Husman, S.; Cluff, R.; Stedman, S.; Thacker, G.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Eight field experiments were conducted across the cotton growing areas of Arizona in 1992 for the purpose of evaluating Upland cotton varieties in terms of adaptability and performance. Five commercial cottonseed companies participated in the program. Two varieties were submitted from each company at each location. Experiments were conducted on grower-cooperator fields in each case except one, which was conducted on a University of Arizona Agricultural Center. Locations used in the program spanned the range of conditions common to cotton producing areas of the state from about 500ft. to 3,000ft. elevation. Results indicated a broad range of adaptability and competitiveness on the part of each of the participating companies and their representative varieties. Each of the companies offers a compliment of varieties that can serve to match various production strategies commonly employed in the state as well as showing a strong capacity to be regionally adaptive.
    • Chemical Control of the Sweetpotato Whitefly in Cotton

      Watson, Theo F.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Both registered and experimental insecticides were evaluated for effectiveness against the sweetpotato whitefly in several field experiments at Yuma, Arizona. Best results were obtained with combinations of two insecticides, particularly a pyrethriod and an organophosphate, rather than with individual materials. Results of these experiments indicate that unusually heavy infestations can be currently controlled even though sustained use of these insecticides would probably lead quickly to the development of resistance.
    • A Comparison of Three Cotton Tillage Systems

      Coates, Wayne E.; Thacker, Gary W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Two reduced cotton tillage systems, both of which utilize controlled traffic farming techniques, are being compared to a conventional tillage system in terms of energy requirements, field work time requirements, crop yield, and operating costs. Four seasons of testing show the Sundance system to have the lowest energy requirement of 28.2 HpHr /Ac, the Uprooter-Shredder-Mulcher (USM) the second lowest at 40.5 HpHr /Ac, and conventional tillage the highest at 54.4 HpHr /Ac. Field work times of the two reduced tillage systems are about one-half that of conventional tillage. Costs of the two reduced tillage systems are lower than for conventional tillage. We have never measured a significantly lower lint yield with either of the two reduced tillage systems, relative to conventional tillage.
    • The Concept of Controlled Traffic Tillage

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      With controlled traffic tillage, the field is divided into "traffic zones" to which all wheel traffic is confined and `production zones" where the plants are grown and there is no wheel compaction. Researchers have shown that using this concept can result in significantly lower tillage costs and field work time than with conventional "broadcast" tillage systems. Most researchers have shown that controlled traffic cotton yields are as high, and are sometimes higher than with conventional tillage. In our research, we have not measured any differences in yield or soil compaction between controlled traffic and conventional tillage systems.
    • Cotton Defoliation Evaluations, 1992

      Silvertooth, J. C.; Husman, S. H.; Brown, P. W.; Burnett, J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Four field experiments were carried out in several representative cotton producing areas of Arizona to evaluate the effectiveness of a number of defoliation treatments on Pima (and Upland) cotton. Somewhat variable but generally hot and dry conditions were encountered among the experimental locations in 1992 for treatment comparisons. It appears that consistencies in the effectiveness of several treatments for Pima defoliation offer a basis for further refinement of recommendations across the state.
    • Cotton Farmer Ratings of Tillage Systems: Important Characteristics and Perceptions of Alternate Systems

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      In a mail survey, we asked Arizona cotton growers which characteristics of a tillage system are important to them. Burial of crop residue, low cost, easy maintenance, reliability, low field work time, and breaking insect life cycles were all rated as important characteristics. Dust control was rated as not important. In rating their perceptions of conventional and alternative tillage systems, cotton farmers indicated that they were not completely satisfied with any of the currently available tillage alternatives.
    • Cotton Response to Applications of PIX, 1992

      Silvertooth, J. C.; Malcuit, J. E.; Hood, L.; Husman, S. H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Four field experiments were conducted in 1992 in Arizona to evaluate cotton crop response to several treatment regimes of multiple applications of PIXTM (an anti - gibberellicacid plant growth regulator). Treatment regimes used in 1992 employed higher rates of PIX/acre /application and extended times of applications later into the fruiting cycle than earlier experiments in 1988 through 1991. Some treatments used exceeded currently labeled maximum use rates in an attempt to evaluate the possible need of increasing maximum rates. Similar to earlier experiments, results in 1992 demonstrated the ability of some PIX treatments to significantly reduce plant height, relative to the untreated check treatments. Excellent fruit retention levels were experienced in each experimental site in 1992, irrespective of PIX treatments. Lint yield results revealed significant differences (P ≤ 0.05) between several selected treatments at two of the locations in 1992.
    • Cotton Row Spacing Study on Long and Short Staple Cotton, Safford Agricultural Center, 1992

      Clark, Lee J.; Carpenter, Eddie W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      A row spacing study was conducted on both long and short staple cotton on the Safford Agricultural Center. The results of this study showed that yields increased from the narrower spaced rows (36 -30 inch and 30 inch spacings) to the wider spaced rows (36 inch and 40 inch spacings). This is the same trend as reported previously with long staple cotton but differs from that previously reported for short staple cotton. Yields of 1.67 and 25 bales per acre for long and short staple cotton were reported.
    • Cottonseed Treatment Evaluations in Arizona, 1992

      Silvertooth, J. C.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Field experiments were conducted at three locations in Arizona (Maricopa, Marana, Safford) to evaluate 9 cottonseed treatments on Upland cotton (G. hirsutum L.). Stand counts were taken to evaluate the effectiveness of each treatment. Statistical analysis showed no significant differences among the treatments used at the Maricopa location. Significant differences were found among the treatments used at the Marana and Safford locations.
    • Defoliation of Pima Cotton at the Safford Agricultural Center, 1992

      Clark, Lee J.; Carpenter, Eddie W.; Odom, Philip N.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Three defoliation studies were performed on Pima cotton at the Safford Agricultural Center in 1992. One tested two different formulations of Dropp with various adjuvants. The second compared experimental material SN597 with other common defoliants. The third compared SN597 at different rates in a late application. At 14 days after application SN597 dropped 97% of the leaves compared to 37% for sodium chlorate. All of the combinations dropped leaves much more efficiently than chlorate.
    • Defoliation Research on Pima and Upland Cotton at the Maricopa Agricultural Center in 1992

      Nelson, J. M.; Hart, G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Field studies were conducted at the Maricopa Agricultural Center to evaluate the effectiveness of selected defoliation treatments on Pima and Upland cotton under warm and cool weather conditions. Weather conditions during September and October defoliation tests were warm and dry. Several cool weather tests in November were terminated by an early frost. Dropp used alone was effective as a single application in September tests, but not in October. In October, Dropp used with the adjuvant Sylgard was superior to Dropp with Agridex and resulted in defoliation similar to Dropp combination treatments. An experimental defoliant, SN597 NA300, was as effective as the Dropp+ Def +Accelerate treatment in October tests with botlu Pima and DPL 90 cotton.
    • The Development and Delivery of a Crop Monitoring Program for Upland and Pima Cotton in Arizona

      Silvertooth, J. C.; Brown, P. W.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      A crop monitoring program has been developed specifically for varieties and environmental conditions unique to Arizona. The monitoring program involves early season development guidelines, growth stage guidelines, and in- season evaluation of crop condition (vegetative /reproductive balance and fruit retention), by use of simple measurements such as height:node ratios (HNR), nodes above the top white bloom (NAWB) counts, and fruit retention estimates from plant mapping. The preliminary work necessary in terms of providing accurate and precise descriptions of the various crop development parameters has been provided through a detailed cotton phenology project conducted over many site years of experimental work. The resultant baselines describing crop development /monitoring parameters have been scaled as a function heat unit (HU, 86/55° F thresholds) accumulations. Application of these baselines have been developed through another facet of the research program to provide a basis for a feedback approach to crop management for inputs such as water, nitrogen (N), plant growth regulators, etc.. The crop monitoring program serves as a fundamental component to an active extension education program being delivered on a statewide basis to all cotton producing areas in Arizona.
    • Differentiation of Sweet Potato Whitefly Biotypes Using RAPD-PCR

      Gawel, N. J.; Bartlett, A. C.; Silvertooth, Jeff; Western Cotton Research Laboratory, USDA -ARS, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      RAPD -PCR was used to detect differences at the DNA level between the A and B forms of B. tabaci. All twenty of the RAPD primers tested distinguished readily between the forms. These primers also distinguished between the forms at the egg and nymph stage. Genetic similarity statistics indicate that these two forms of B. tabaci were no more closely related to each other than to bayberry whitefly (Parabemisia mvricae) or bandedwinged whitefly (Trialeurodes abutilonea). DNA from B. tabaci collected from 11 locations around the world was also analyzed. These insects could be classified into six distinct groups, suggesting there are more than two variant forms of B. tabaci. A comprehensive examination of all variant types of B. tabaci will have to be conducted before a concise definition of the taxonomic relationship between the 'A' and 'B' forms can be determined.
    • Drought Tolerance in the Progeny of Interspecific Cotton Hybrids

      McDaniel, R. G.; Dobrenz, A. K.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The F2 and F3 progeny of interspecific cotton crosses were evaluated under field conditions. The plants were maintained under drip irrigation with stress applied by withholding water during plant development and early flowering periods. Physiological and biochemical plant responses were measured throughout the growing season on an array of representative plants from the field population. Considerable variability was found to exist among these progeny for all traits measured in both years of the present study. Responses of parental controls were quite consistent for both seasons.
    • Early Season Irrigation Effects on Low Desert Upland Cotton Yields Using Leaf Water Potential Measurements

      Husman, S. H.; Garrot, Donald J. Jr.; O'Leary, J. W.; Ramsey, C. S.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Leaf water potential (LWP) measurements using a pressure chamber were used to determine optimum timing of the first irrigation following planting on Upland cotton. Previous studies have indicated that leaf water potentials are dependent on the vapor pressure deficit (VPD) of the surrounding air. As a result, the VPD was accounted for in the development of a Leaf Water Potential Index (LWPI). The field study consisted of three irrigation treatments with four replicates arranged in a randomized complete block design (RCBD). Targeted treatment thresholds were 0.15 LWPI (wet), 0.30 LWPI (medium), and 0.45 LWPI (dry). Timing of the first irrigation occurred at 36, 53, and 63 days after planting for the wet, medium, and dry treatments respectively. There were no significant lint yield differences between irrigation treatments.
    • Effect of Foliar Applications of PGRIV on Yield of Pima and Upland Cotton

      Nelson, J. M.; Hart, G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The commercial product PGRIV was tested in small plots on cotton at the Maricopa Agricultural Center. Multiple foliar applications of this product had no significant effect on lint yield of Pima S-7 and DPL 90 cotton.
    • Effect of Plant Water Status on Defoliation and Yield of Pima Cotton

      Nelson, J. M.; Bartels, P. G.; Hart, G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      A field study was conducted at the Maricopa Agricultural Center to determine the influence of plant water status at the time of defoliation on the effectiveness of defoliants and yield of Pima cotton. Irrigation termination dates of 4 and 18 September and 2 October were used to achieve different levels of plant water stress at the time defoliants were applied (16 October). Irrigation termination dates tested had no significant effect on lint yield or the effectiveness of defoliants. All irrigation termination dates resulted in defoliation of 80% or higher using a single application of defoliants. At the time of defoliation, CWSI values ranged front 0.59 to 0.80 and plant water potential from -2.0 to -2.9 MPa for the three irrigation termination treatments.
    • The Effect of Water Stress on Two Short-Season Cultivars of Cotton, Gossypium hisutum L., and the Sweetpotato Whitefly, Bemisia tabaci Genn

      Flint, Hollis M.; Wilson, F. D.; Hendrix, D.; Leggett, J.; Naranjo, J.; Henneberry, T. J.; Radin, J. W.; Silvertooth, Jeff; Western Cotton Research Laboratory, USDA -ARS, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Deltapine 50 (DP -50) and Stoneville 506 (ST -506), short season cultivars of upland cotton, Gossvpium hirsutum L., were grown under weekly or biweekly irrigation schedules in 0.2 ha plots in a split plot design at Maricopa, AZ. The seasonal average numbers of sweetpotato whitefly eggs and nymphs were 24% greater on leaves of plants irrigated biweekly. The leaves of ST-506 had 26% greater numbers of eggs and nymphs than did leaves of DP -50. Samples of lint from the two cultivars irrigated biweekly had 32 % more sugar than did lint from the cultivars irrigated weekly (weekly = 0.28 ± 0.02% , biweekly = 0.41% ± 0.03% sugar). Our results indicate that the numbers of immature sweetpotato whitefly on cotton plants can be reduced by 47% by selecting a less susceptible cultivar and avoiding plant water stress.
    • The Effects of Foliar Applies Potassium Thiosulfate on Upland Cotton Lint Yield and Fibert Quality

      Husman, Stephen H.; Doerge, Thomas; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      A replicated field study was conducted at the Maricopa Agricultural Center in 1992 investigating Upland cotton lint yield and fiber quality response to foliar applied potassium thiosulfate. Applications were applied at early, peak, and late bloom. There were no significant yield or lint quality response by treatment.