• Sweetpotato Whitely Control on Cotton by Treating Only the Field Edges

      El-Lissy, Osama; Antilla, Larry; Butler, George D. Jr.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The edges of one of each of five pairs of long staple cotton fields were treated for sweetpotato whiteflies. Treated fields had 61% fewer eggs and 53% fewer nymphs than untreated fields. Adult populations were reduced 64% in the treated fields at the edges. In the center of treated fields adult populations remained low and unchanged but in untreated fields there was a 70% increase. According to minicard tests, cotton from treated fields was not sticky but cotton from untreated fields was sticky. Thus, populations of whiteflies and their damage can be significantly reduced by treating only the periphery of cotton fields at the onset of infestation. The treating of only 12 to 15% of the acreage greatly reduces costs and preserves the untreated center for beneficial insects.
    • 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.
    • Sweetpotato Whitefly (Bemisia tabaci Gennadius) Control: Field Studies with Insecticides on Cotton in the Imperial Valley, CA

      Chu, C. C.; Henneberry, T. J.; Akey, D. H.; Silvertooth, Jeff; Western Cotton Research Laboratory, USDA -ARS, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Insecticides and insecticide mixtures were evaluated for sweetpotato whitefly (Bemisia tabaci Gennadius) control on cotton in the Imperial Valley, CA in 1992. Seasonal average number of large immatures was 1.6/cm² leaf disk from plots treated with a mixture of Danitol and Orthene as compared to 4. 5/cm² on leaf disks from untreated control plots. Lint yield was 1232 lbs/ac compared to other treatments which ranged from 551 to 976 lbs /ac.
    • 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.
    • 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.
    • Weather Conditions Associated with Outbreaks of Severe Whitefly Infestations in Arizona

      Brown, P. W.; Watson, T. F.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      An analysis of weather conditions prior to and during the severe sweet potato whitefly (SPWF) outbreaks of 1981 and 1992 in Arizona revealed some striking similarities. Both bad outbreaks were preceded by 1) weak monsoons during the summer preceding the outbreak (1980 and 1991); 2) winters with very warm minimum temperatures and no incidence of extreme cold; and 3) springs with above normal temperatures and precipitation. The analysis also revealed the presence of above normal minimum temperatures during most winters since SPWF became an important pest in the Desert Southwest.
    • 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.
    • Management of Pre-Harvest Aflatoxin Contamination of Cottonseed Using Beneficial Bacteria

      Misaghi, I. J.; Cotty, P. J.; DeCianne, D. M.; Silvertooth, Jeff; Department of Plant Pathology, University of Arizona; USDA/ARS, Southern Regional Research Center (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The overall goal of our study is to find effective and environmentally sound methods to reduce pre -harvest aflatoxin contamination of cottonseed in Arizona. The specific objectives are: 1) to screen a large number of bacteria for their ability to destroy the aflatoxin producing fungus, Aspeigillus flavus; 2) to test the efficacy and consistency of the recovered antagonistic bacterial isolates to reduce aflatoxin contamination of cottonseed in field trials; 3) to study the survival and competitiveness of the antagonists on cotton plants under prevailing field conditions; 4) to find innovative procedures to enhance survivability and competitiveness of the antagonists on cotton plants; and 5) to test the potential of the bacterial antagonists to reduce the population of A. flavus in field soils. Over 800 bacterial isolates, recovered from cotton field soils, cotton leaves, stems, and immature as well as opened bolls, were tested for ability to inhibit the growth of A. flavus on cottonseed. Six isolates partially or totally inhibited the fungus. All of these effective isolates prevented the fungus fioin infecting simulated pink bollworm exit holes in immature bolls in the field.
    • Evaluation of the Pressure Chamber for Timing Early Season Irrigations

      Brown, P.; Silvertooth, J.; Malcuit, J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Use of the pressure chamber to time the initial post- planting irrigation of short season upland cotton was evaluated in a pilot study at Marana during 1992. Top yields and better overall plant performance were obtained when the initial post - planting irrigation was applied before leaf xylem potential (ψx) dropped significantly below -15 bars. Our findings were similar to those previously observed with Acala cotton in California. The authors believe more work is required before use of the pressure chamber is recommended for irrigation management in Arizona. Specifically, an effective means of separating changes in ψx resulting from day-to-day climate fluctuations from those caused by soil-water depletion must be developed. This study also clearly showed the importance of avoiding early season water stress when growing short season cotton.
    • The Use of AZSCHED to Schedule Irrigation on Cotton, Safford Agricultural Center - 1992

      Clark, Lee J.; Carpenter, Eddie W.; Slack, Donald C.; Martin, Edward C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      AZSCHED Irrigation scheduling software was used on Pima and upland cotton with irrigations being scheduled at 40, 50 and 60% water depletion. Around 8 inches of rain fell during the growing season so no statistical differences were seen between treatment yields.
    • 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.
    • Pima Cotton Genetics

      Percy, R. G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Two investigations, one of the inheritance of stomatal regulation and its relation to heat tolerance and the other of seed gossypol content in Gossvpium barbadense, began yielding results in 1992. Mode of gene action conferring stomatal conductance varied with the parentage of crosses. Selective advance for high conductance appeared to be feasible in wide crosses, but limited in crosses of elite Pima strains. Variability for seed gossypol content in G. barbadense was surprisingly high. There was evidence of geographic and taxonomic structure to the variability observed. A conversion program to convert photoperiodic short-day flowering accession's of the G. barbadense germplasm collection to day neutrality continued.
    • Pima Cotton Improvement

      Percy, R. G.; Turcotte, E. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Pima experimental strains P73, P74, P75, P76, P77, P79 and the varieties Pima S-6 (PS-6) and Pima S-7 (PS-7) were grown in replicated Regional tests at ten locations across the Pima belt in 1992. Tests were machine harvested for yield determination, plant heights were measured, and fiber samples were collected for fiber analysis. Considerable genotype by environment interaction for yield potential occurred across tests in 1992. Across all locations, the cultivar PS-7 ranked first in yield followed by the strains P79 and P75. The cultivar PS-6 was the tallest entry in the tests, followed by P75. The strains P76, P77, and P79 were uniformly shorter. Considering yield and fiber properties concurrently, strain P75 was the superior strain entry of the 1992 tests.
    • Pima 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)
      Twelve pima varieties were grown in a replicated trial at the Maricopa Agricultural Center as part of the National Cotton Variety Testing Program.
    • Short Staple Variety Trial, Greenlee County, 1992

      Clark, Lee J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Two New Mexico acalas, one California acala, two upland hybrids and two other upland varieties were evaluated in a two-part trial at one location in Greenlee county in 1992. The New Mexico acalas topped the trial with 1517-91 having the highest yield with 2227 pounds of seed cotton per acre.
    • 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.
    • 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.
    • 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.
    • 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.
    • Multiple Plant Growth Regulator Use on Short Staple Cotton

      Hood, L. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      A field trial was initiated during the 1992 growing season to evaluate the activity of Cytokin and Piz applied alone or in combination to short staple cotton. The Cytokin treatment significantly increased lint yield over the other treatments. There were no statistically significant differences between the non-treated check and any other treatment. The Cytokin treatment increased lint yield an average of 81 pounds over the check plots. Fruit retention remained high throughout the season, indicating that Pix would not normally have been needed.