• Germination and Respiration of Cotton Seed Produced in Arizona

      Dobrenz, Albert K.; Silvertooth, Jeffrey C.; Martin, Jill; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The germination percentage and seedling respiration were evaluated on 11 cultivars of Cotton produced in Arizona. Respiration rates of 5-day old seedlings ranged from 6.0 to 16.9 mg /g⁻¹ hr⁻¹ for DP -5690 and KC-311, respectively. Germination percentage ranged from 31 to 87% for KC-311 and DP-51, respectively. A significant negative correlation (r = -.90) between respiration rates and the germination percentage indicates that seed quality is closely associated with early seedling metabolic rates.
    • 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.
    • Sequential Sampling Plans for Bemisia Tabaci Eggs and Nymphs in Cotton

      Naranjo, Steve E.; Flint, Hollis M.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Fixed precision sequential sampling plans are reported for egg and nymphal stages of Bemisia tabaci on cotton. These plans were developed based on detailed examination of within -leaf, within plant, and within field distributions of egg and nymphal (crawler through pupae) stages during the 1992 growing season in central Arizona. The most efficient sample unit for eggs and nymphs was determined to be a single 3.88 cm2 circular plug taken from the basal portion of the 2nd sector of the 5th mainstem node leaf (counted from the terminal). Tentative plans are presented relating cumulative counts to sample size for fixed levels of precision.
    • Performance of Selected Insecticides Against the Sweetpotato Whitefly and Cotton Aphid

      Ellsworth, P. C.; Meade, D. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Seven insecticides were evaluated in nine treatment combinations for efficacy against the sweetpotato whitefly (SPWF) and the cotton aphid (CA). Five different classes of chemistry were represented by these compounds, which were compared to an untreated check. The infestation was characterized as severe (> 300 SPWFs/sq. in.) and included a substantial number of CAs at the beginning of the evaluation ( >90 /leaf). Three applications were made in August after the onset of "stickiness." For SPWFs, three treatments compared favorably with the check, but only after three applications Orthene +Danitol, Capture alone, and Capture +Ovasyn. Intermediate control was achieved with Endosulfan +Ovasen. Rankingsfor CA control were dissimilar with Vvdate +Asana, Endosulfan +Ovasen, and Ovasen alone consistently performing better than the check. Vvdate alone, Endosulfan alone, and Orthene +Danitol were intermediate in CA control, but also significantly different from the check. Capture alone and Capture+Ovasyn which performed well for SPWF control was not efficacious against CAs. Indeed the two single pyrethroid treatments (Capture: Asana) failed to achieve any degree of CA control.
    • 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.
    • 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.
    • Weather Conditions during the 1992 Growing Season

      Brown, P.; Russell, B.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Abundant rainfall was the most prominent feature of the 1992 growing season. Monthly precipitation totaled above normal during the first five months of the year, and during August and December. Warm temperatures accompanied the wet weather during the spring planting season and helped boost growing season heat unit totals to near record levels in central and western Arizona. Early fall weather was warm and dry which provided excellent conditions for both finishing the crop and preparing the crop for harvest.
    • Potassium Fertility of Several Arizona Soils

      Unrah, B. L.; Silvertooth, J. C.; Hendricks, D. M.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Potassium (K) fertility requirements for cotton ( Gossypium spp) have been a matter of concern due to increasing interest and emphasis on fiber quality and numerous reports of K deficiencies in various cotton producing regions. To address this matter appropriately, a thorough understanding of the chemical, physical, and mineralogical composition of the soils in question is in order. Soil samples were collected from ten sites across southern Arizona that are representative of the common agricultural soils of the region. At all locations soils were sampled to a depth of 120 cm in 30 cm increments. All soils were characterized with respect to chemical composition by the following parameters: exchangeable K, total K, cation exchange capacity and particle size analysis. With the exception of one soil (a soil not commonly employed in cotton production), none of the chemically characterized soils contained less than 150 mg K kg⁻¹ of extractable K in the surface 90 cm of soil. All of the soils contained K- bearing mica and none of the soils contained any K- fixing vermiculite. From the initial chemical and mineralogical information, K fertilization is not likely for similar situations in Arizona. Further research is under way to quantify the K-fixing ability of each soil in this survey and additional field studies are also being conducted to evaluate K fertilization in both Upland (G. hirsutum L.) and Pima (G. barbadense L.) cotton.
    • Long and Short Staple Cotton Variety Trial, Safford Agricultural Center, 1992

      Clark, L. J.; Carpenter, E. W.; Nelson, J. M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Thirty six short staple varieties and thirteen long staple varieties were grown in a replicated field trial on the Safford Agricultural Center in Graham county. Stoneville 324 was the highest yielding short staple variety in the trial with a yield of 4733 pounds per acre of seed cotton. The average yields of short staple varieties was greater than in 1991. Long staple cotton did not fare as well with the weather as did the short staple. The yield of S-6 was about 100 pounds of seed cotton less than in 1991. The good news is that other long staple varieties are being developed that can out yield S -6 in the high desert area. O & A Pima was the highest yielding variety with a yield that exceeded S-6 by about 500 pounds of seed cotton per acre. S-7 followed closely behind O & A Pima 4 and both matured quicker than S-6. Heat unit data from the past couple of years are given in this report along with the average heat unit accumulation.
    • Short Staple Variety Demonstration, Graham County, 1992

      Clark, Lee J.; Cluff, Ronald E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Twelve upland cotton varieties were compared in an on farm trial in Graham county. The highest yielding variety was Stoneville 324, a relatively new semi-smooth- leafed variety from Stoneville with fiber qualities that approach those of DPL 90. Stoneville 324 yielded 4226 pounds of seed cotton with HS Sal 10 following closely behind at 4158 pounds per acre.
    • Upland Regional Cotton Variety Test, Maricopa Agricultural Center, 1992

      Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Eighteen short staple varieties were grown in a replicated trial at the Maricopa Agricultural Center as part of the National Cotton Variety Testing Program.
    • Evaluation of Date of Planting and Irrigation Termination on the Yield of Upland and Pima Cotton, 1992

      Silvertooth, J. C.; Watson, T. F.; Malcuit, J. E.; Brown, P. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Six field experiments were conducted at three locations in 1992 in Arizona to evaluate the response of Upland and Pima cotton to dates of planting and dates of irrigation termination. Planting dates ranged from as early as 11 March in the Yuma Valley (150 ft. elevation) to 30 April at Marana (2,000 ft. elevation). Dates of irrigation termination ranged from 15 July in the Yuma Valley to 18 September at Maricopa. Planting date was commonly a significant effect in these experiments, particularly with Pima cotton. Irrigation termination results over three locations and four seasons show increases of approximately 60 to 120 lbs. lint /acre by extending later irrigations.
    • Sweetpotato Whitefly Control: Enhancement of the Repellency of Oils

      Butler, George D. Jr.; Henneberry, T. J.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The repellency to adult SPW of 1% Saf -T -Side and 1% Natur'1 Oil was enhanced by the addition of Butracide + Pounce, Butracide + Pyrellin, or a pyrethrum + diatomaceous earth. Several materials containing pyrethrum appeared to improve the repellency of 2% Saf -T -Side. The number of eggs laid was correlated with the number of adults observed on the plants, thus emphasizing the importance of the repellency of SPW adults. Three oils at 1% concentration gave a high mortality of SPW nymphs. Several materials killed nymphs when applied with a fine spray, simulating the deposit of a mist blower.
    • Expression of Insectical Protease Inhibitors in Arizona Cotton

      Thomas, John C.; Bohnert, Hans J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Insect damage impacts tremendously on the value of the Arizona cotton crop. As traditional pesticides become increasingly less useful, due to insect resistance and regulatory problems, new methods for insect control are needed. For these reasons, we engineered genes encoding protease inhibitors (PIs) from Manduca sexta (tobacco hornworm), for expression in cotton, with the hope that these inhibitors would have insecticidal activity. Transgenic plants containing PIs have been generated: 22 fertile lines of the duplicated 35S promoter anti-elastase, 4 fertile lines of the anti -chymotrypsin and 5 fertile lines of the anti -trypsin. Over 3,000 T-1 seeds have been collected and T-2 generation seeds are in production. Many crosses have been made into Delta Pine 16, 90 and 5415 respectively. No significant effect of the PIs on boll number or seed yield was observed. Insect tests have been conducted and the results indicate that plants expressing the protease inhibitors (PI's) have decreased emergence of whiteflies compared to control plants. We believe this research is a significant step towards a bio- pesticide producing Arizona cotton variety.
    • Impact of Temperature and Relative Humidity on Defoliation of Pima S-7 and Deltapine 5415 Cotton Treated with Dropp (Thidiazuron)

      Bartels, Paul G.; Easley, Jack; Nelson, John; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Chemical defoliation of cotton is a cultural practice that induces abscission of cotton foliage earlier than normal leaf shedding. Early cotton defoliation is an integral part of short- season cotton production because it facilitates the mechanical harvesting of cotton and helps reduce insect population in late summer. Effectiveness of the chemical defoliants depends upon the environmental conditions at the time of application. Research was conducted to access the impact of temperature, relative humidity (RH), and water stress at time of defoliation on effectiveness of thidiazuron (Dropp) a chemical defoliant to defoliate cotton grown under field and growth chamber conditions. Humidity was increased by spraying a fine mist over the cotton canopy. Plant moisture stress was achieved by terminating irrigation of cotton at selected times before defoliation. In growth chambers, the greatest defoliation of Pima S -7 and Deltapines 5415 cotton treated with Dropp occurred at day /night temperatures of 32C/18C with 80% RH whereas, lowest defoliation occurred at day /night temperatures of 40C /19C and 22C/9C with 80% RH. In the field, irrigation termination dates of Sept 4, Sept 18, and Oct 2, 1992 were evaluated for their effect on defoliation of Pima S -7 cotton defoliation on Oct 16, 1992 with Dropp. The Sept 4 irrigation termination date resulted in higher percent defoliation than Oct 2 irrigation termination date 14 days after Dropp was applied.
    • 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.
    • The Effects of PIX Application Timing on Upland Cotton Lint Yield and Growth and Development Parameters

      Husman, S. H.; Silvertooth, J. C.; Ramsey, C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Four commercial scale field studies were conducted in 1991 and 1992 to further evaluate Upland cotton yield and development responses to PIX application timing as a function of cotton growth stage. Treatments imposed in both years intended to further clarify some response trends observed in previous years of field studies. Treatments were all at the maximum label rate of one and one half pints with application timing the main variable. Timing was based on heat unit accumulation and resultant growth stage since date of planting. Two of the four studies resulted in significant lint yield increase of roughly one hundred pounds across all PIX treatments in contrast to the untreated check. The two studies which resulted in lint yield increases both had height:node ratio measurements in excess (vegetative) of previously defined guidelines.
    • Sweetpotato Whitefly Natural Enemies: Parasite Surveys in Urban Areas and Cotton Fields and Identification of a New Predator

      Butler, George D. Jr.; Henneberry, T. J.; Silvertooth, Jeff; Western Cotton Research Laboratory, USDA -ARS, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Surveys for adult sweetpotato whitefly parasites on ornamentals in urban areas and in cultivated cotton fields show high parasite activity in urban areas vs. activity in cultivated cotton fields. A previously unreported Drapetis spp. fly was identified and found to occur in cotton fields in several areas in the state.
    • Preliminary Investigation of Sweet Potato Whitefly Population Dynamics Across Arizona

      Nelson, Merritt; Orum, Thomas; Byrne, Thomas; El Lissy, Osama; Antilla, Larry; Staten, Robert; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The sweet potato whitefly can have an impact on cotton by reducing yields through direct feeding damage, by transmitting the cotton crumple leaf virus during feeding and by the production of large amounts of sticky honeydew that interferes with the harvesting and ginning process. Data on whitefly populations collected weekly from 938 yellow sticky traps near cotton fields have been entered into a geographic information system (GIS) database. In general, whitefly populations were high near cotton fields in the Yuma area before July 6th. They rose rapidly in central Arizona between July 6th and July 20th. During the month of August, counts continued to rise in central Arizona, particularly in western Pinal County. Populations began to fall during October. Whitefly populations in eastern La Paz County were slower to develop than in other areas in western Arizona. Whitefly populations in Graham and Cochise County were not significant throughout the growing season. Cotton crumple leaf virus was observed in parts of central and western Arizona.
    • 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.