• 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • Sweetpotato Whitefly Preference and Performance on Medium Maturity Cotton Varieties in Arizona

      Ellsworth, P. C.; Meade, D. L.; Husman, S. H.; Ramsey, C. S.; Silvertooth, J. C.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      In conjunction with the 1992 cotton variety testing program (see Silvertooth 1993), 12 medium maturity varieties were evaluated for the presence of sweetpotato whitefli.es (SPWF). Three sites (Queen Creek, Maricopa, Coolidge) were selected for expression of a full range of infestation intensity. Total immatures per square inch ranged from less than 8 up to more than 8(X), depending on site, sample date and variety. The results indicated that there were significant effects of variety on SPWF numbers; however, the ranking of varieties was not always the same nor significant. Most varieties performed comparably, but one consistently had more SPWFs than the remaining varieties (chi 1 35). Comparative results from the three sites indicate that there may be separate preference and performance components which lead to the development of an infestation. Lea f hairiness was quantified front samples at one site, and the relationship of this factor to whitefly susceptibility is discussed. Two varieties, cb1135 and stv453, were found to be significantly more hairy than the remaining varieties. The results provided here represent a preliminary evaluation of the data. Further analyses will attempt to relate various crop production and agronomic factors to SPWF susceptibility (e.g., plant height, fruit retention, height:node ratio, canopy closure, growth habit, maturity, yield, crop protection regimen). One fact was clear, however. None of the varieties evaluated here demonstrated resistance to SPWFs and certainly not to the extent that a producer could eliminate substantial risk of infestation through variety selection.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • HVI Lint Quality as Affected by Defoliation Treatments, Marana 1991

      Thacker, Gary; Odom, Phil; Silvertooth, Jeff; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      This study was conducted to determine the effect of various defoliation treatments on the HVI quality of short staple cotton. We compared two applications of sodium chlorate and Accelerate to single applications of Dropp plus crop oil with and without Accelerate. We measured significant differences in percent defoliation and desiccation. We also measured significant differences in the HVI parameters of staple, micronaire, and length.