• Silverleaf Whitefly: Honeydew Sugars and Relationship to Sticky Cotton

      Henneberry, T. J.; Hendrix, D. L.; Perkins, H. H.; Forlow Jech, L.; Burke, R. A.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ; USDA-ARS, SAA, Clemson, SC (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      In cotton plots heavily infested with silverleaf whitefly (SLW), Bemisia argentifolii Bellows and Perring, amounts (mg /g of lint) of sugar (fructose, glucose and sucrose combination) on lint from tagged bolls, varied but showed a general trend to increasing amounts with increasing time of exposure (days) for 52 days. Minicard lint stickiness ratings responded in a similar manner and all values were above acceptable thresholds. Lint from harvested mature open bolls that were exposed on trays suspended in the interior of SLW infested cotton plots showed increasing amounts of sugar and higher minicard ratings after 6 days. Amounts of sugar and minicard ratings were drastically reduced following rains of 1.5 inches.
    • 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.
    • Host Preference of Silverleaf Whitefly and Factors Associated with Feeding Site Preference

      Chu, C. C.; Hennberry, T. J.; Cohen, A. C.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Silverleaf whitefly (SLW), Bemisia argentifolii, Bellows and Perring, preferred cantaloupe to cotton, broccoli and lettuce in field and greenhouse studies. In the absence of cantaloupe, SLW preferred cotton to broccoli and lettuce. In the field, more eggs and fewer nymphs were found on broccoli than on cotton. Differences in the relative abundance of vascular bundles per unit of leaf area between the four plant species may partly account for differences in oviposition site selection. Vascular bundle volume/unit of leaf tissue volume was 50% greater in cantaloupe than in cotton and broccoli, which in turn were significantly greater than in lettuce. Most SLW on cotton leaves are found on underside leaf surfaces. Distances from top and underside leaf surfaces to the nearest vascular bundles in cotton leaves were 131 and 60 tun, respectively, in the present studies.
    • Short Staple Variety Demonstations, Graham County, 1994

      Clark, Lee J.; Cluff, Ronald E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Two on farm, replicated short staple variety demonstrations were established in 1994. Fifteen varieties were evaluated on the Layton farm in Thatcher and eighteen varieties were evaluated on the Colvin farm in Eden. Several new varieties were planted in both studies. Stoneville 324 and HS 46 were the highest yielding varieties with yields of 1060 and 975 pounds of lint per acre at the Thatcher and Eden locations, respectively.
    • Determining Soil Moisture for Irrigation Management

      Martin, E. C.; Husman, S.; Wegener, R.; Brown, P.; Johnson, K.; Schnakenberg, L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      One key component in good irrigation management is the measurement of soil moisture to help determine when to irrigate. In this study, resistance blocks and tensiometers were compared to neutron probe readings to assess how well these devices followed soil moisture and whether the resistance blocks and /or tensiometers could be used to schedule irrigation in cotton production. The resistance blocks were placed at 6, 18, and 30 inches. Tensiometers were placed at 18 and 30 inches. The readings from the resistance blocks and tensiometers were compared to neutron probe readings taken at 6, 18, and 30 inches. The resistance blocks compared well with the neutron probe readings at the 6 inch and 30 inch depth. At the 18 inch depth, there was much scatter in the data. The tensiometers also showed good comparisons at 30 inches and poor comparisons at 18 inches.
    • Comparison of Irrigation Scheduling Methods in Cotton Production

      Martin, E. C.; Pegelow, E. J.; Stedman, S.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Three different irrigation scheduling techniques were compared in this study; aerial infrared, hand -held infrared, and neutron moisture gage measurements. There were four treatments with three replications of each. Treatment one was scheduled using aerial infrared imaging and analyzes performed by Agrometrics, Inc. Treatment two was scheduled using a hand -held infrared gun. Irrigations for this treatment were initiated at a crop water stress index value of 0.3. Treatments three and four were scheduled using neutron probe measurements. Treatment three was irrigated at 45% depletion of the available soil water. Treatment four was irrigated at 45% depletion of the available soil water until mid-bloom, when the strategy was changed to irrigate at 35% depletion. Yield results showed no significant difference between the treatments.
    • 1994 Cottonseed Treatment Evaluations

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Cottonseed was treated with several fungicide treatments in an effort to protect the seed and seedling from disease. Seed germination and vigor was evaluated in three Arizona locations; Maricopa, Marana, and Safford. Stand counts were taken on two separate dates after emergence at both Safford and Marana and once at Maricopa and percent emergence was calculated. Among the three locations two, Marana and Safford, showed significant differences among treatments. Treatment number 5 placed first at both locations where significant differences were found. The untreated control placed last in the ranking at both Marana and Safford for all dates of sampling.
    • Pima Regional Variety Test; Maricopa Agricultural Center, 1994

      Hart, G. L.; Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Nine Pima varieties and experimental 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.
    • Pima Cotton Improvement

      Moser, H. S.; Percy, R. G.; Ray, I. M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      The objective of this study was to evaluate the performance of five experimental lines (P73, P75, P76, P80, and P81) with two commercial varieties ('Pima S-6' and 'Pima S-79 of Pima cotton. All seven strains were grown in replicated strip tests at four locations across the Pima belt in 1994. While none of the experimental lines produced significantly more lint than the best Pima variety at any site, some of them possess traits that are valuable to Pima cotton breeders. P73 has long and strong fiber. P76 is a high yielding, early maturing line that produces long and strong fiber. P80's lint yields are similar to Pima S-7, but it is significantly earlier.
    • Chemical Control of the Sweetpotato Whitefly in Cotton

      Watson, T. F.; Tellez, M. A.; Peña, M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Various registered and experimental insecticides were evaluated for sweetpotato whitefly (Bemisia tabaci Gennadius) control in several field experiments at Yuma, Arizona in 1994. Best controls were obtained with insecticide mixtures, particularly a pyrethroid and an organophosphate, rather than with individual materials. Results of these experiments indicate that severe population densities can be controlled using insecticide combinations, even though sustained use of these insecticides would probably lead quickly to the development of resistance.
    • The 1995 Arizona Cotton Advisory Program

      Brown, P.; Russell, B.; Silvertooth, J.; Ellsworth, P.; Stedman, S.; Thacker, G.; Husman, S.; Cluff, R.; Howell, D.; Winans, S.; et al. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Arizona Cooperative Extension generates and distributes weather -based Planting Date and Cotton Development Advisories for 11 cotton production areas (Marana, Laveen, Paloma, Litchfield Pk., Pinal Co., Parker, Mohave Valley, Queen Creek, Safford, Yuma Valley, and Aguila). Planting Date Advisories are distributed from mid- February through the end of April and stress 1) planting 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 development, insects, weather and agronomy. The Cotton Advisory Program will continue in 1994 and growers may obtain the advisories by mail or fax from the local county extension office, and by computer from the AZMET computer bulletin board. Improved normal weather statistics and the addition of an advisory for Cochise County are the main changes planned for the 1995 program.
    • 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.
    • Pima Cotton Regional Variety Trial, Safford Agricultural Center, 1994

      Clark, L. J.; Carpenter, E. W.; Hart, G. L.; Nelson, J. M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Ten long staple varieties (including two Pima experimental lines) were tested in a replicated small plot trial on the Safford Agricultural Center in Graham county at an elevation of 2950 feet. Even though the total number of heat units received during the season was nearly as high as the previous year, the average yield was nearly 300 pounds per acre lower. Olvey and Associates OA 304 was the highest yielding variety with a yield of 776 pounds per acre of lint and only two varieties broke the bale and a half mark. Yield and other agronomic data as well as fiber quality data are contained in this paper.
    • 1994 Weather Conditions

      Brown, P.; Russell, B.; Silvertooth, J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      The 1994 cotton production season began with near optimal weather conditions. Temperatures and precipitation during planting and early vegetative growth were near optimal levels and were generally near normal. Summer brought an extended period of high day and night temperatures which began in June and continued through September at most locations. The period of high temperature associated with the monsoon (July and August) coincided with a rapid decline in fruit retention across much of the state. While the monsoon provided the usual rise in night temperature and humidity, summer rainfall was relatively light at most locations. Early fall weather was warm and dry, providing generally good conditions for finishing the crop. Weather conditions then cooled dramatically in the late fall prior to the onset of heavy rains in December. The wet December conditions limited post harvest field work in many locations.
    • 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.
    • Crop Water Use Estimates

      Watson, J.; Sheedy, M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Irrigation scheduling, by keeping track of irrigation applications, soil storage and crop water use, has been computerized by a number of different individuals. A key component of the computerized methods is the estimation of a reference crop evapotranspiration rate. Complaints about one such method, AZSCHED, led the authors to compare the reference crop evapotranspiration values calculated by AZSCHED with those calculated by a second procedure available used by AZMET. Results of the comparison indicated that no significant difference existed between methods, for either a traditionally "long season", or a contemporary "short season" growing period. AZSCHED did estimate crop water use to be about 5% - 8% more than AZMET, an amount that is not of importance considering the irrigation inefficiencies created by field non-uniformities. Experience by the authors indicates that inappropriate selection of irrigation efficiencies and/or soil water holding capacity may be the main cause of user complaints.
    • Effect of Planting Date on Yield of Upland and Pima Cotton Varieties at Marana

      Unruh, B. L.; Silvertooth, J. C.; Brown, P. W.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      A single field experiment was conducted at Marana Agricultural Center (2000 fl elevation) to evaluate the response of one Pima (G. barbadense L) and two Upland (Gossypium hirsutum L.) cotton varieties to three different planting dates. Planting dates ranged from 12 April to 16 May. In general there was decreasing lint yield with later planting dates.
    • The Interaction and Effects of Soil Moisture Regime and Yellow Nutsedge (Cyperus esculentus) Density on Cotton (Gossypium hirsutum) Growth

      Moffett, Jody E.; McCloskey, William B.; Husman, Stephen H.; Dixon, Gary L.; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, Arizona; Cooperative Extension, Maricopa County, Phoenix, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      The goal of our research is to determine the effects of yellow nutsedge competition on cotton and to examine how the competitive relationship between these two species is modulated by soil moisture. In support of this goal, a competition experiment with various nutsedge densities and three irrigation regimes was conducted at the University of Arizona, Maricopa Agricultural Center. The results of this study indicate that increasing nutsedge density caused a significant linear decrease in cotton seed yield in both 1993 (p=0.03) and 1994 (p=0.002). The cotton yield reductions caused by the highest nutsedge densities, 33 and 50 tubers /m of crop row in 1993 and 1994, respectively, were 13.5 and 15.5 percent, respectively. Stem biomass, an indicator of total above ground biomass, increased significantly with increasing soil moisture. There was also a trend of increasing seed cotton yield with increasing soil moisture with the wet treatment (i.e., irrigation at 35 percent soil moisture depletion) resulting in the highest biomass and yields. In 1994 this trend was significant (p=0.0001) but in 1993 it was not (p=0.098) probably because fewer replications were used in 1993. An important goal of this research was to determine if cotton, with its deeper tap root type of root architecture, is more competitive against yellow nutsedge, which has a fibrous root system, when irrigation is less frequent. However, analysis of variance showed that there was no significant interaction between soil moisture availability and seed cotton yield reductions caused by nutsedge competition in either 1993 (p=0.44) or 1994 (p=0.62).
    • Evaluation of Soil Conditioners and Water Treatments for Cotton Production Systems

      Unruh, B. L.; Silvertooth, J. C.; Sanchez, C. A.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1995-03)
      Advanced technologies to produce synthetic polymers such as polyacrylamide (PAS, and polymaleic anhydride (PMA) have produced products which may be economically feasible alternatives to traditional treatments such as gypsum in the desert Southwest. In 1994 three field studies were initiated, two identical studies were located in the Yuma Valley and one at Paloma Ranch. At Yuma Valley the experiments included 0, 1, and 2 tons gypsum/acre, over which, various soil-applied treatments were made; including, a check, soluble PMA (Sper Sal™), and PAM (Hydro-Growth™). Upland cotton 'DPL 5461' was grown in both Yuma Valley studies. At Paloma Ranch, Upland 'DPL 5415' planted. Prior to planting, two gypsum applications were made at 0 and 2 tons/acre. Also included as treatments were various methods and rates of Sper Salt™. No differences among treatments were detected in either of these locations relative to crop yield. At Paloma Ranch there were some early-season differences in soil crusting among the various soil amendment treatments, however, these differences dissipated as the season progressed and did not result in lint yield differences.
    • 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