• 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.
    • The Development and Delivery of a Crop Monitoring Program for Upland and Pima Cotton in Arizona

      Silvertooth, J. C.; Brown, P. W.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      A crop monitoring program has been developed specifically for varieties and environmental conditions unique to Arizona. The monitoring program involves early season development guidelines, growth stage guidelines, and in- season evaluation of crop condition (vegetative /reproductive balance and fruit retention), by use of simple measurements such as height:node ratios (HNR), nodes above the top white bloom (NAWB) counts, and fruit retention estimates from plant mapping. The preliminary work necessary in terms of providing accurate and precise descriptions of the various crop development parameters has been provided through a detailed cotton phenology project conducted over many site years of experimental work. The resultant baselines describing crop development /monitoring parameters have been scaled as a function heat unit (HU, 86/55° F thresholds) accumulations. Application of these baselines have been developed through another facet of the research program to provide a basis for a feedback approach to crop management for inputs such as water, nitrogen (N), plant growth regulators, etc.. The crop monitoring program serves as a fundamental component to an active extension education program being delivered on a statewide basis to all cotton producing areas in Arizona.
    • Trap Crops as a Component of a Community-Wide Pink Bollworm Control Program

      Thacker, Gary W.; Moore, Leon; Ellsworth, Peter C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Trap crops were employed against the pink bollworm (PBW) as a part of a community-wide IPM program in Pima County, AZ. Levels of PBW larvae in the early squares of the trap crops were extraordinarily high, indicating that the trap crops were drawing overwintered PBW moths in from wide areas. This concentrated the overwintered moths in small areas where they could be easily and economically destroyed.
    • Upland and Pima Cotton Response to Soil and Foliar Potassium at Three Arizona Locations

      Unrah, B. L.; Silvertooth, J. C.; Clark, L. J.; Nelson, J.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Due to a limited information describing the response of cotton (Gossvpium spp.) in Arizona to K fertilization, three studies were conducted in 1992 with the objective of evaluating the response of cotton crop growth and lint yield to soil and/or foliar applications of K fertilizer. The locations of the trials included the Safford Agriculture Center (Pima clay loam), Maricopa Agriculture Center (Casa Grande sandy loam), and a site located near Coolidge, AZ on a Mohall sandy loam soil. All irrigation, pest management, and fertilization inputs (other than K) were provided on an as- needed basis throughout the season. Routine plant measurements and plant mapping analyses were carried out at each location on regular intervals throughout the season. At the Safford location both Upland (G. hirsutum L., var DPL 90) and Pima (G. barbadense L., var S-6) cotton were planted with treatments including soil and foliar K applications imposed in a factorial arrangement. All soil K applications were broadcast and preplant incorporated using K₂SO₄ as the K source at rates of 0, 200, and 400 lbs. K₂O/acre. Four 4.6 lbs K₂O /acre foliar applications of KNO₃ were applied at 1626, 2016, 2326, and 2510 heat units after planting (HUAP). The trial at the Maricopa Agriculture Center included four foliar K applications over the growing season applied to Pima cotton (S-6) at 2427, 2762, 3200, and 3515 HUAP. The six foliar treatments included rates which ranged from 0 to 37 lbs. K₂O /acre using KNO₃ as the K source. Treatments were arranged over the experimental area in a randomized complete block design with five replications. At Coolidge all K treatments were band-applied to the soil at a depth of 8 in. using two shanks per row, preplant. The treatments were 0, 218, 436, and 654 lbs. K₂O /acre using K₂SO₄ as the fertilizer source. Upland cotton (STV KC311) was planted and treatments were arranged in a randomized complete block design with four replications. Results from all three trials indicated no differences among any of the treatments (including soil verses foliar and unfertilized treatments). All of the plant measurements taken for all the locations reveal crop growth resulting in excellent fruit retention without vegetative growth (i.e. height-to-node ratios within the long -term 95% confidence intervals for both Upland and Pima cotton. This indicates ample nutrient demand so that if available soil K is inadequate to meet crop needs, deficiency symptoms and reduced yields should occur. No visual deficiency symptoms were detected for any treatment in the experiments (all locations). All plots experienced vigorous and wellbalanced growth and development throughout the growing season. The results of these K fertility experiments supports current University of Arizona recommendations that unless exchangeable K is less than 150 ppm, crop response is not likely, although an exact critical level for exchangeable K is still lacking.
    • Nitrogen Management Experiments for Upland and Pima Cotton, 1992

      Silvertooth, J. C.; Clark, L. J.; Malcuit, J. E.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Two field experiments were conducted in Arizona in 1992 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. The effects of N fertility levels were evident in crop maturity and its relationship to lint yields.
    • 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.
    • Irrigation Efficiencies, Nitrogen and Phosphorous Applications, and Lint Yields of Upland Cotton Grown at the Maricopa Agricultural Center, 1992

      Sheedy, Mike; Watson, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The computer program AZSCHED, with weather data obtained from AZMET, was used to schedule irrigations for a yield trial of Upland Cotton (DPL 90) at the Maricopa Agricultural Center. Cotton lint yields were compared between plots from eight treatments involving the combination of two irrigation efficiencies (70% and 90%), two nitrogen fertilizer placements (sidedressed and broadcast), and two phosphate fertilizer applications (0#/a and 50#/a). A potassium bromide (KBr) tracer was applied to select areas in each plot prior to the first irrigation. The total amount of fertilizer as nitrogen applied in split applications to both the sidedressed and broadcast plots was 120 #/a. The average amount of water applied to the plots were 33.5" for 70 % efficiency and 26.9" for 90% efficiency. Soil samples from each KBr applied 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. The plots were harvested on October 7, 1992. This year there was no significant difference in lint yield between any of the treatments: irrigation efficiencies, nitrogen placement, or phosphorous application.
    • 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.
    • The Effect of Water Stress on Two Short-Season Cultivars of Cotton, Gossypium hisutum L., and the Sweetpotato Whitefly, Bemisia tabaci Genn

      Flint, Hollis M.; Wilson, F. D.; Hendrix, D.; Leggett, J.; Naranjo, J.; Henneberry, T. J.; Radin, J. W.; Silvertooth, Jeff; Western Cotton Research Laboratory, USDA -ARS, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Deltapine 50 (DP -50) and Stoneville 506 (ST -506), short season cultivars of upland cotton, Gossvpium hirsutum L., were grown under weekly or biweekly irrigation schedules in 0.2 ha plots in a split plot design at Maricopa, AZ. The seasonal average numbers of sweetpotato whitefly eggs and nymphs were 24% greater on leaves of plants irrigated biweekly. The leaves of ST-506 had 26% greater numbers of eggs and nymphs than did leaves of DP -50. Samples of lint from the two cultivars irrigated biweekly had 32 % more sugar than did lint from the cultivars irrigated weekly (weekly = 0.28 ± 0.02% , biweekly = 0.41% ± 0.03% sugar). Our results indicate that the numbers of immature sweetpotato whitefly on cotton plants can be reduced by 47% by selecting a less susceptible cultivar and avoiding plant water stress.
    • 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.
    • 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.
    • Cotton Farmer Ratings of Tillage Systems: Important Characteristics and Perceptions of Alternate Systems

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      In a mail survey, we asked Arizona cotton growers which characteristics of a tillage system are important to them. Burial of crop residue, low cost, easy maintenance, reliability, low field work time, and breaking insect life cycles were all rated as important characteristics. Dust control was rated as not important. In rating their perceptions of conventional and alternative tillage systems, cotton farmers indicated that they were not completely satisfied with any of the currently available tillage alternatives.
    • Cottonseed Treatment Evaluations in Arizona, 1992

      Silvertooth, J. C.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Field experiments were conducted at three locations in Arizona (Maricopa, Marana, Safford) to evaluate 9 cottonseed treatments on Upland cotton (G. hirsutum L.). Stand counts were taken to evaluate the effectiveness of each treatment. Statistical analysis showed no significant differences among the treatments used at the Maricopa location. Significant differences were found among the treatments used at the Marana and Safford locations.
    • 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 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.
    • 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.
    • High Rate PIX Use on Upland Cotton

      Hood, L. R.; Silvertooth, J. C.; 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 high rate Pix use on upland cotton. The cotton field used for this trial maintained high fruit retention and low to moderate height-to-node ratios throughout the growing season. Fix treatments at label and above label rates both significantly reduced lint yield compared to the non-treated check This reinforces the concept of a feedback approach using crop monitoring (vs scheduled inputs according to calendar dates) to make management decisions on crop inputs.
    • 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.
    • 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.