• 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.
    • 1991 Cotton Replant Decisions, Safford Agricultural Center

      Clark, Lee J.; Carpenter, Eddie W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Each planting season in the Safford valley there are fields that suffer stand reduction from adverse weather conditions. This study addresses some of the options and the economical effects from exercising these options on a field at the Safford Agricultural Center. References are made to work in California that have quantified the yield effect of stand reduction and chilling damage to cotton seedlings. This study shows that patience may pay better than rushing into the field to replant or rewater.
    • Defoliation of Pima Cotton, 1991

      Silvertooth, J. C.; Husman, S. H.; Stedman, S. W.; Brown, P. W.; Howell, D. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Four field experiments were carried out in several representative cotton producing areas of Arizona to evaluate the effectiveness of a number of defoliation treatments on Pima cotton. Somewhat variable but generally hot and dry conditions were encountered among the experimental locations in 1991 for treatment comparisons. It appears that consistencies in the effectiveness of several treatments for Pima defoliation offer a basis for further refinement of recommendations across the state.
    • 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.
    • Effect of Plant Nitrogen Status on Defoliation of Short-Season Upland Cotton

      Nelson, J. M.; Hart, Gary; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Field studies have been conducted over a four year period at the Maricopa Agricultural Center to determine the influence of nitrogen (N) fertility level on the effectiveness of chemical defoliants for short- season cotton production. Excessive N resulted in dense foliage and cotton that was difficult to defoliate. When plants were deficient in N from mid-season to termination, defoliants were very effective, but lint yields were reduced. The effectiveness of defoliants decreased as the petiole NO₃-N content increased. The optimum fertility program for short-season cotton is one that provides sufficient N during the season to produce maximum lint yields, but allows the crop to become deficient in N at the end of the season, prior to chemical defoliation.
    • Effect of Plant Water Status on Defoliation and Yield of Upland Cotton for Short-Season Production

      Nelson, J. M.; Bartels, P. G.; 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 determine the influence of plant water status at the time of defoliation on the effectiveness of defoliants and yield of short-season cotton. Irrigation termination dates of 14 and 26 August and 10 September were used to achieve different levels of plant water stress at the time defoliants were applied (19 September). Irrigation termination dates had no effect on seedcotton yield for cotton defoliated in September. As the period between the termination irrigation and the date of chemical defoliation was increased the effectiveness of defoliants was increased. CWSI and plant water potential measurements indicated that the irrigation termination dates resulted in large differences in plant water stress at defoliation time. There was a significant increase in the defoliation percentage as CWSI values increased (from 0.32 to 0.96) and water potential decreased (from -1.5 to -3.5 MPa). Short- season cotton (163 days) produced 4,396 lbs. seedcotton /A as compared to 5,299 lbs./A for a full-season crop (212 days).
    • Leafminers, Liriomyza trifolii, on Cotton in Arizona

      Palumbo, John C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Liriomyza leafminers have occurred in Arizona for several years. It has only been recently that a new species, Liriomyza trifolii, has been reported on vegetable crops such as melons and lettuce. During the 1991 growing season, L. trifolii was observed causing damage to cotton for the first time in Central Arizona. Infestations occurring in Coolidge, had reached damaging levels and required control, whereas populations occurring in Yuma were very low. The impact of management and environmental factors responsible for the outbreaks of L. trifolii on cotton are discussed.
    • 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.
    • A Native Weed as a Trap Crop for Whiteflies in Cotton

      Ellsworth, Peter C.; Chernicky, Jon P.; Byrne, David N.; Gibson, Roberta; Meade, Donna; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A field study was conducted during 1991 to evaluate the effectiveness of Physalis wrightii Gray, as a trap crop for Bemisia tabaci (Gennadius) when grown with the commercial crop Gossypium barbedense L. Aldicarb at two rates was used in P. wrightii for control of B. tabaci. Three sampling methods: pan counts, leaf turns, and leaf counts measured B. tabaci numbers in both crops. Aldicarb treatment in the trap crop did significantly affect B. tabaci populations in comparison with untreated P. wrightii (P= 0.000, df =2, 240). Differences in numbers of adults observed on the two hosts were not significant. Analysis of aldicarb metabolite residues by high pressure liquid chromatography exhibited a pronounced dose effect (P= 0.001, df =2, 22) in the trap crop leaf tissues. The chemically treated trap crop did significantly protect the cotton crop from larger and more rapidly developing sweetpotato whitefly populations when compared to the untreated check.
    • Physiological Studies of Cotton Drought Tolerance

      McDaniel, R. G.; Dobrenz, A. K.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      We evaluated an array of progeny of interspecific cotton crosses in the field. Significant water stress was placed on the plants in mid-summer by withholding water supplied by drip irrigation during plant development earlier in the season. A number of physiological measurements were carried out on selected individual plants of this population during the several week period of imposed drought stress. Overall results confirm that a large degree of variation exists within the population for all traits measured. Initial carbon isotope discrimination measurements suggest this trait may prove useful in estimating transpiration efficiency of cotton genotypes.
    • 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.
    • Upland Cotton Resposne to Soil and Foliar Applies 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.
    • Cottonseed Treatment Evaluations in Arizona, 1991

      Silvertooth, J. C.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Field experiments were conducted at three locations in Arizona (Maricopa, Marana, Safford) to evaluate 12 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 Marana location. Significant differences were found among the treatments used at the Maricopa and Safford locations.
    • Cotton Yields: Nitrogen and Harvest Aid Effects

      Chu, Chang-chi; Henneberry, Thomas J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      The results of field studies with N rates from 0 to 336 kg/ha, in combination with two growth regulators, ethephon (Prep® ɑ-chloroethyl phosphonic acid, Rhone-Poulenc Ag Co., Research Triangle Parr NC) and thidiazuron (Dropp® N- phenyl -N' -1,2,3 -thiadiazol -5ylurea, Nor-Am Ag Prod. Inc., Naperville, IL). Results showed that sidedress applications of N (ammonium nitrate) to cotton did not influence the defoliation effects of ethephon and thidiazuron, or reduce number of immature green bolls at harvest. Under short-season conditions, sidedress N applications did not effect yields. Ethephon and thidiazuron at the rates tested did not affect cotton lint yields. Thidiazuron alone or in combination with ethephon resulted in high percentages of cotton defoliation.
    • Defoliation Research on Pima and Upland Cotton at the Marana Agricultural Center in 1991

      Nelson, J. M.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A field study was conducted at the Marana Agricultural Center to evaluate the effectiveness of ground rig applied defoliant treatments on Pima and Upland cotton under cool weather conditions. Defoliants were slow acting at this location, however, all chemical treatments tested resulted in good defoliation 14 days after application.
    • Pima Cotton Genetics

      Percy, R. G.; Turcotte, E. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      An investigation was conducted to determine the inheritance, allelism, and linkage associations of a spontaneous, male- sterile mutant found in plants of American Pima (Gossypium barbadense L.) cotton. Analyses of F₁, F₂, and BC populations of the mutant indicated that it was inherited as a single, recessive gene. T ests for allelism of the new gene with three previously described recessive male - sterility genes (ms₁, ms₂ and ms₃) were negative. Analyses of F₂ population segregation from crosses to 23 mutant marker stocks produced no evidence of linkage associations. We have proposed that the male sterility mutant be designated male-sterile-13 and be given the gene symbol ms₁₃. A conversion program to convert photoperiodic short-day accessions of a Gossypium barbadense germplasm collection to day neutrality continues.
    • 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.
    • Community-wide Insect Management Program in Pima County, 1991

      Moore, Leon; Thacker, Gary; Watson, Theo; Ellsworth, Peter; Combs, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      The Marana-Avra Growers' Task Force and Arizona Cooperative Extension worked together to implement a comprehensive, community-wide insect management program. Growers worked in unison to implement a number of Integrated Pest Management techniques; including uniform optimal planting dates, trap cropping, pinhead square spray applications, in-season insect management, and late season management. This strategy focused on the area's primary pest, the pink bollworm (PBW). This program delayed the need to treat for PBW until late August and minimized secondary pest problems. However, research results on the effectiveness of trap crops were inconclusive.
    • Evaluation of Date of Planting and Irrigation Termination on the Yield of Upland and Pima Cotton

      Silvertooth, J. C.; Watson, T. F.; Malcuit, J. E.; Brown, P. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Five field experiments were conducted at three locations in 1991 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 2 April in the Yuma Valley (150 ft. elevation) to 14 May at Marana (2,000 ft. elevation). Dates of irrigation termination ranged from 8 August in the Yuma Valley to 24 September at Maricopa. Planting date was commonly a significant effect in these experiments, particularly with Pima cotton. Irrigationtermination results over three locations and three seasons show increases of approximately 50 to 100 lbs. lint /acre by extending later irrigations.
    • 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.