• Plant Population Effects on Pima S-6 Lint Yield

      Husman, S. H.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A replicated field study was conducted at the Maricopa Agricultural Center in 1991 to investigate the effect of plant population density on Pima S-6 lint yield. Treatments ranged from a low of 10,465 plants per acre to a high of 65,000 plants per acre. There were no significant yield differences observed with populations between 17,000 plants per acre and 65,000 plants per acre. Significant yield decreases occurred when populations were reduced below 17,000 plants per acre.
    • Defoliation Research on Pima and Upland Cotton at the Maricopa Agricultural Center in 1991

      Nelson, J. M.; Hart, G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A field study was conducted at the Maricopa Agricultural Center to evaluate the effectiveness of selected defoliant treatments on Pima and Upland cotton under warm and cool weather conditions. In September tests, no defoliant treatment was effective in a single application. Upland cotton that was injured by frost in late October was difficult to defoliate in November tests. Pima cotton exhibited less frost injury than Upland and all defoliant treatments resulted in good defoliation in November.
    • Short Staple Variety Trial, Cochise County, 1991

      Clark, Lee J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Three new California acala varieties are evaluated in this field trial along with nine New Mexico acalas. The highest yielding variety was New Mexico's 1517-88 with a yield of 2.8 bales per acre. California's MAXXA came in number 3, but not very far behind, yieldwise. Nazas 77, a rust resistant variety from Mexico,was evaluated in a second trial at this same location. Rust was not a problem at this site in 1991 so its rust- resistance could not be evaluated, but it yielded within 5% of the yield of 1517-88.
    • Late-Season PIX Treatment for Cotton Termination

      Nelson, J. M.; Hart, G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A field study was conducted at the Maricopa Agricultural Center to evaluate the effect of a late - season application of PIX on Upland cotton termination. A 28 August application of PIX or FIX + Prep had only a small effect on late-season growth and no effect on defoliation or yield.
    • Defoliation of Pima Cotton at 3000 Feet Elevation, Safford Agricultural Center, 1991

      Clark, Lee J.; Carpenter, Eddie W.; Odom, Phil; Nelson, John; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A preliminary study of several defoliants and /or combinations was made on the Safford Agricultural Center. Even though conditions were less than ideal because of cool temperatures, acceptable defoliation occurred under several of the treatments. In fact, three of the treatments performed better than sodium chlorate, which is the predominant defoliant used in the area.
    • Sweetpotato Whitefly: Flight Activity, Effects of Wind Velocity, and Precopulatory Pairing Activity Patterns

      Butler, George D. Jr.; Henneberry, T. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Sweetpotato whitefly (SPW), Bemisia tabaci (Gennadius), exhibited high levels of flight activity during daylight hours from July to September. Flight activity in a fallow field in Arizona in late August began as early as 0600 h, peaked between 0800 and 0900 h, and decreased thereafter during the day. Flight activity in cultivated cotton, lettuce and alfalfa fields also occurred throughout the day in early and late September. Few SPW were caught between 1900 and 0700 h. Peak numbers were caught on sticky traps prior to 1200 h in Arizona and Israel. Numbers of adults caught on sticky traps decreased from 0700 to 1000 h and with increasing wind velocity. Precopulatory pairing behavior occurred as early as 0700 h and increased gradually to 0900 to 0920 h, when 48% of the adults observed were paired, and decreased thereafter.
    • Cotton Row Spacing Studies, Safford Agricultural Center

      Clark, Lee J.; Carpenter, Eddie W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A row spacing study was conducted at the Safford Agricultural Center from 1989 to 1991, evaluating the effects of 40 inch, 36 inch, 36-30 inch and 30 inch row spacing on Pima and upland cotton. The results of the study are not clear cut in favor of narrow or wide row cotton. Trends make it appear that narrow rows are more favorable for upland than Pima cotton varieties. Insufficient data is available at this point to make a firm recommendation.
    • Revised Planting Window for Full Season Cototn Varieties

      Brown, P.; Silvertooth, J.; Moore, L.; Watson, T.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A heat-unit-based planting window was introduced in 1991 as a means of reducing early season problems with pink bollworm (PBW). Growers were encouraged to plant full season varieties when the annual heat unit (HU) accumulation ranged between 600 and 900 -- a window designed to ensure 75% suicidal emergence of PBW yet maintain acceptable yield levels. New research findings and a reexamination of past PBW emergence studies now support making an adjustment to the planting window. For 199Z the recommended planting window is 450 - 700 HUs after January 1.
    • Nitrogen Management Experiments for Upland and Pima Cotton, 1991

      Silvertooth, J. C.; Clark, L. J.; Malcuit, J. E.; Carpenter, E. W.; Doerge, T. A.; Watson, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Two field experiments were conducted in Arizona in 1991 at two locations (Maricopa and Safford). 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. Results at both locations 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.
    • Irrigation Efficiencies, Nitrogen Applications, and Lint Yields of Upland Cotton Grown at the Marcopa Agricultural Center, 1991

      Sheedy, Mike; Watson, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      The computer program AZSched, with weather data obtained from AzMet, was used to schedule irrigation for a yield trial of Upland Cotton (DPL 90) at the Maricopa Agricultural Center in 1991. Cotton lint yields were compared between plots from four treatments involving the combination of two irrigation efficiencies (70% and 90 %) and two nitrogen fertilizer applications (broadcast and sidedress). The amount of nitrogen fertilizer applied to the broadcast plots was 145# N /A. One hundred thirty pounds NIA was applied to the sidedressed plots. A potassium bromide tracer was applied to select areas in each plot at the time of initial fertilization. Soil samples from each plot were taken to a depth of 10' for analysis of bromide and nitrate to determine the depth of water movement through the soil profile. Irrigation amounts averaged 42.8" for 70% efficiency and 36.7" for 90% efficiency. No significant difference in lint yield was noticed between the two nitrogen fertilizer applications, but significant differences existed between the two irrigation efficiencies.
    • Effects of Planting Date on the Yield of Cotton Varieties at Yuma, Arizona

      Malcuit, J. E.; Silvertooth, J. C.; Howell, D. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A field experiment was conducted in Yuma, Arizona to evaluate the effects of planting date on cotton yields. Six Upland varieties were planted on 3 dates from 15 March to 24 April in 1991. Significant differences were found among varieties at the first planting date (15 March) with full season varieties yielding higher than medium and short season varieties. No differences were found among varieties at planting dates 8 April and 24 April. Significant differences were found among planting dates for all varieties. Weather conditions in March were abnormally cool and may have negatively influenced yields from the first planting date.
    • 1991 Yuma County Upland Cotton Variety Trial, Wayne Stuhr Farm - Wellton, AZ

      Howell, Don R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
    • The Arizona Cotton Advisory Program

      Brown, P.; Russell, B.; Silvertooth, J.; Moore, L.; Stedman, S.; Thacker, G.; Hood, L.; Husman, S.; Howell, D.; Cluff, R.; et al. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Arizona Cooperative Extension produced and distributed weather -based Planting Date and Cotton Development Advisories for 8 cotton production areas (Marana, Litchfield Pk, Pinal Co., Parker, Safford, Yuma Valley, Dateland and Aguila) in 1991. Planting Date Advisories were distributed from mid - February through the end of April and stressed 1) planting full season cotton varieties according to heat unit accumulations rather than calendar date and 2) the importance of soil temperature to good germination. Cotton Development Advisories were distributed from early May through mid- September and provided growers updates on crop development, insects, weather and agronomy. The Cotton Advisory Program will continue in 1992 with the major change being an expansion in coverage to include Paloma, Queen Ck, and Mohave Valley.
    • Upland Cotton Response to Soil and Foliar Applied Potassium Fertilizer, 1991

      Silvertooth, J. C.; Husman, S. H.; Malcuit, J. E.; Doerge, T. A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A single field experiment was conducted near Gila Bend, Arizona in 1991 to evaluate the effects of both soil and foliar applied potassium (K) fertilizersto Upland (Gossvpium hirsutum L.) cotton to a soil testing 315 ppm K (high). Soil applied K fertilizer at rates of 0, 75,150, and 225 lbs. K₂O/acre as K₂SO₄ were broadcast and preplant incorporated before listing. Foliar applications were made in all combinations with the various soil applied K treatments and consisted of four applications of 4.6 lbs. K₂O /acre as KNO₃ (10 lbs. KNO₃ /acre) over the first fruiting cycle, by a ground applicator with approximately 25 gallons per acre as carrier. No differences among treatments were detected by any plant growth measurement taken, plant tissue analyses, lint yield or lint quality determinations which were made over this experiment. Conclusions (preliminary) based upon these results indicate that K fertilization was not warranted under the conditions characterized in this single field experiment.
    • Seasonal Dynamica of Sweetpotato Whitefly

      Watson, T. F.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      The sweet potato whitefly (SPWF) Bemisia tabaci (Gennadius). has become a serious problem of a number of agricultural crops in the southern tier of states in the U.S. In the southwestern U.S. it seriously affects summer crops such as melons and cotton, and fall, winter and spring vegetable crops such as lettuce, broccoli and cauliflower. Since this insect has no overwintering resting stage a succession of host plants is necessary in order to span the gap from cotton season to cotton season. This study characterized seasonal population trends of SPWF in cotton and then identified subsequent hosts which were important in the overwintering survival of this insect. The "off-season" hosts included certain weeds as well as cultivated crops and all appear to be important in the seasonal population dynamics of this whitefly.
    • Water Stress Effects on Pima Cotton Lint Yields Using Infrared Thermometry to Schedule Irrigations

      Husman, S. H. .; Garrot, D. J. Jr.; Moore, M.; Ramsey, C; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      The Crop Water Stress Index (CWSI) was used to schedule irrigations on Pima S-6 cotton on a commercial scale in Waddell, Ariz. in 1991. The field study consisted of sixteen, one acre, surface irrigated plots. There were four water treatments with four replicates arranged in a randomized complete block design. There were no significant lint yield differences among water treatments. However, an additional two irrigations totalling an acre foot of water were needed to maintain the treatment thresholds.
    • Inundative Release of Trichogrammatoidea bactrae for Biological Control of Pink Bollworm

      Naranjo, Steven; Gordh, Gordon; Moratorio, Mario; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Replicated, small-plot studies were conducted in 1991 to evaluate control of pink bollworm (PBW), Pectinophora gossypiella, by inundative releases of a newly imported Australian egg parasitoid, Trichogrammatoidea bactrae. Weekly release of parasitoids at equivalent rates of 165,000/HA beginning in mid-June significantly reduced egg and larval populations of PBW in comparison with control plots until mid-August, but provided no control thereafter. Rates of parasitism on artificially-placed PBW egg cards exceeded 90% until mid-July and then declined, becoming somewhat variable over the latter half of the season. Parasitism rates dropped near zero on three dates coinciding with drift from aerial pesticide application at a neighboring cotton field. The seasonal decline in rates of parasitism was not significantly related to increasing plant leaf area, vigor of released parasitoids, or ambient temperature. Parasitism of indigenous PBW eggs on cotton bolls was extremely low and this, along with moth migration from surrounding cotton, may have contributed to the lack of mid- to late-season control in our small plots. Results are encouraging and suggest that larger-scale release studies are warranted.
    • Cotton Crop Growth and Development Patterns

      Silvertooth, J. C.; Brown, P. W.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Summaries of cotton crop phenology, as a function of heat units (HU, 86/55 °F limits) have been developed across a wide range of production conditions in Arizona. Optimum ranges of HU accumulations since 1 January are used to describe optimal planting dates for full season varieties. Basic events such as the occurrence of pinhead squares, squares susceptible to pink bollworm, and first bloom are described in terms of HU accumulations since planting. Fruit retention guidelines and height: node ratios measures a crop's vegetative/reproductive balance, are developed as a function of HUAP. The use of the number of nodes above the top white bloom to the terminal (NAWB) is developed as a measure of a crops progression towards cut-out. Also, the expected ranges of HU 's accumulated since planting that are required to accomplish crop cut-out are shown for three general maturity types of Upland cotton.
    • Short Staple Variety Demonstrations, Graham County, 1991

      Clark, Lee J.; Cluff, Ronald E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Weather played a major part in the production of cotton in the Safford valley in 1991. A cool spring and early summer slowed the development of cotton and gave an advantage to varieties that could produce quickly in the warm late summer months. Three Stoneville varieties came to the top of the test with Stoneville 506 producing the highest yield of over 4000 pounds of seed cotton per acre. The New Mexico acalas, 1517-91 and 1517-88 also produced well, and depending on the premium, could produce more income per acre than the top varieties. Fifteen varieties were tested at this site and all produced over 2 bales per acre.
    • Cotton Variety Trial, Safford Agricultural Center, 1991

      Clark, Lee J.; Carpenter, Eddie W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Forty one short staple varieties and Pima S-6 were grown in a replicated field trial on the Safford Agricultural Center in Graham county. Most of the varieties were commercially available in the cotton belt, however, a few experimental varieties from the New Mexico acalas, ChemBred and from Delta Pines were included. Yields were 15 to 30% lower than the yields in this trial in 1990, with only one variety producing more than 4000 pounds of seed cotton per acre. The top variety was CB (ChemBred) 407 with a yield of 4177 pounds per acre. HS Sal 10, which was number two last year, retained that position in 1991. Newcomers to the top ten were: S1001, HS 46, CBX 1210, DP 5690, STV 506 and DP 5415. Heat unit data from the past couple of years are given in this report along with the average heat unit accumulation.