• Boll Sampling to Predict Lint Yield in Upland and Pima Cotton

      Unrah, Bryan L.; Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Giving a cotton (Gossypium spp.) producer a method to predict lint yield, would be a useful management tool. The objective of this study was to determine if relatively simple measurements could be made near cut -out which could be used to adequately estimate lint yield for Upland (G. hirsutum L.) and Pima (G. barbadense L.) cotton. Data and samples were collected from the nitrogen (N) management study at Maricopa Ag. Center from two N treatments which were imposed on both Upland (var. DPL 5415) and Pima (var. S-7) cotton. The treatments were no added N and N added on an as- needed basis. Twenty hard -green bolls from the first or second fruiting positions were collected from each plot on 19 August 1993. The number of bolls expected to reach maturity prior to crop termination were then determined from five randomly selected plants in each plot. Measurements on each boll collected included fresh weight, diameter, number of locks, number of seeds, and dry seed cotton weight. Plant population was determined from early season stand counts. Seed cotton per boll was most highly correlated to boll weight for DPL 5415 and for Pima S-7 it was most highly correlated with boll diameter. These respective parameters were then used in linear regression to predict seed cotton /boll. Lint yield calculated from the regression models (using boll weight or diameter) and yield calculated from means of the data collected agreed quit well. Predicted yields from regression analysis overestimated the actual Upland yield by about 730 lb lint /acre and under estimated Pima yields to within about 150 lb lint /acre. It appears that this procedure has the potential to estimate lint yields to within about 150 lb lint /acre. However the sampling scheme will he refined especially in regard to estimation of plants /acre and bolls /plant which should improve yield estimate accuracy.
    • Chemical Control of the Sweetpotato Whitefly in Cotton

      Watson, T. F.; Telles, A.; Peña, M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Various registered and experimental insecticides were evaluated for sweetpotato whitefly (Bemisia tabaci Gennadius) control in several field experiments at Yuma, Arizona in 1993. Best controls were obtained with insecticide mixtures, particularly a pyrethroid and an organophosphate, rather than with individual materials. Results of these experiments indicate that severe population densities can be controlled using insecticide combinations, even though sustained use of these insecticides would probably lead quickly to the development of resistance.
    • A Community-wide Approach to Whitefly Management

      Diehl, J. W.; Ellsworth, P. C.; Husman, S. H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      An extension supported, grower controlled, community pest management group was initiated in the Laveen and Tolleson communities of Arizona with the management of sweetpotato whitefly (SPWF) as its initial focus. The three functions of this group were awareness, communication, and cooperation. Increased awareness and communication of pest management problems and solutions were achieved through regular meetings and newsletters. Community cooperation took the form of a community-based overwintering survey and a sticky trap network. These two cooperative activities served both an educational and a research function. From the overwintering survey and the sticky trap network, growers learned about the overwintering habits and movement dynamics of whiteflies in their area, the limits of sticky traps for SPWF detection, the need for the reduction of SPWF populations before they move onto cotton. and the need for careful infield sampling of SPWF populations.
    • A Comparison of Three Cotton Tillage Systems: Six Year Summary

      Coates, Wayne E.; Thacker, Gary W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Two reduced cotton tillage systems, both of which utilize controlled traffic farming techniques, were compared to a conventional tillage system in terms of energy requirements, field work time requirements, crop yield, and operating costs. Six seasons of testing show the Sundance system to have the lowest energy requirement of 31.95 Hp- Hr /Ac, the Uprooter -Shredder-Mulcher the second lowest at 47.16 Hp- Hr /Ac, and conventional tillage the highest at 66.89 Hp- Hr /Ac. Field work times of the two reduced tillage systems were about 58% 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.
    • Control of Sweepotato (Silverleaf) Whitefly, Bemisia Tabaci, on Cotton in Paloma, Arizona

      El-Lissy, O.; Antilla, L.; Staten, R. T.; Leggett, J. E.; Walters, M.; Silvertooth, Jeff; Arizona Cotton Research and Protection Council, Phoenix, AZ; USDA-Animal and Plant Health Inspection Service, Phoenix, AZ; USDA-ARS-Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      A large scale for the control of sweetpotato (silverleaf) whitefly, Bemisia tabaci, (SPW) was carried out in Paloma and Painted Rock near Gila Bend, Arizona, on approximately 6,156 ha of cotton during the 1993 season. Within the program area 40 fields were randomly selected for comparison with 15 fields in each of 2 locations outside the program. They were identified as check east (approximately 11 k northeast of the program) and check west (approximately 3 k west of the program). Whitefly populations in both check areas were controlled according to individual grower protocol. On a weekly basis, adult counts were taken from all 4 edges and the centers of each field using the oil pan technique. Insecticides were applied aerially in the program area on the full field or edges based on population density recorded from pan samples. Insecticide combinations were rotated weekly in an attempt to reduce the potential for the development of pesticide resistance. During the 16 -week evaluation period SPW adults were significantly higher in check east and check west than the program area by 2- and 6-fold respectively; eggs were higher by 3- and 39 fold, respectively; and nymphs were also significantly higher in check east and check west by 3- and 60-fold respectively. Ginning records for 1993 indicate approximately a 20% increase in yield in the program area a 5% increase in check east and a 40% decrease in check west as compared to 1992. These results demonstrate that an area -wide approach, utilizing edge treatment where possible, based on extensive field sampling regimens represent an important integrated strategy in a successful whitefly control program.
    • Cotton Defoliation Evaluations, 1993

      Silvertooth, J. C.; Stedman, S. W.; Cluff, R. E.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Three field experiments were carried out in several representative cotton producing areas of Arizona to evaluate the effectiveness of a number of defoliation treatments on Upland cotton. These experiments were conducted at Coolidge, Marana, and Safford and utilized defoliation treatments designed for their potential effectiveness finder cooler weather conditions commonly experienced later in the defoliation season and at higher elevations. The treatments employed also offer potentials for use in close proximity to urban areas due to not having offensive odors associated with them. All treatments showed promise in terms of effectiveness and the results provide a basis for use recommendations in 1994 as well further points of study in future experiments.
    • Cotton Producers Working in Unison: The Multi-Component IPM Program in Marana, AZ

      Thacker, Gary W.; Ellsworth, Peter C.; Moore, Leon; Combs, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Cotton growers in Pima County, Arizona are working together to implement a community-wide Integrated Pest Management program. Participation is voluntary; and is unanimous in at least some components of the program. The IPM program employs many control components aimed at the pink bollworm, the principle cotton insect pest in the area. Growers time the deployment of the control components to act in unison throughout the community. Insecticide applications in the area have trended downward since the program began in 1991, indicating that we are making progress toward our goal of reducing the reliance on pesticides.
    • Cultural and Management Practices for Pima Cotton Production

      Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      The good use of cultural or agronomic practices is fundamental to the production of high yields and quality of American Pima cotton. In order for Pima farmers to maintain viable production operations, a continual review and improvement upon the existing set of cultural practices are in order. Basic aspects of crop production such as planting date management, soil fertility and plant nutrition, plant growth regulator use, crop termination, and defoliation are reviewed in this paper in relation to American Pima cotton production. Specific attention is also given to potassium (K) fertility management and Alternaria leaf spot regarding new aspects of potential management needs.
    • Defoliation of Pima and Upland Cotton at the Safford Agricultural Center, 1993

      Clark, L. J.; Carpenter, E. W.; Odom, P. N.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Experiments were effected on both Pima and upland cotton to compare the defoliation effects of Ginstar, Starfire and sodium chlorate with an untreated check Weather conditions after treatment applications were recorded and observations taken after one week and two weeks. Grab samples were taken from the picker to determine percent trash and to run HVI analyses.
    • Defoliation Research on Pima and Upland Cotton at the Marana Agricultural Center in 1993

      Nelson, J. M.; Barney, G. F.; Hart, G. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      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 condition. The experimental defoliant Ginstar and the combination treatment of Dropp + Def resulted in good defoliation 14 days after application.
    • Defoliation Research on Pima and Upland Cotton at the Maricopa Agricultural Center in 1993

      Nelson, J. M.; Hart, G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Field studies were conducted at the Maricopa Agricultural Center to evaluate the effectiveness of selected defoliation treatments on Pima and upland cotton under warm and cool weather conditions. Weather conditions during September tests were warm and dry while in late October tests weather was very cool. Defoliation treatments resulted in a high percentage of leaf desiccation in a test on 10 September. Ginstar and Dropp + Def treatments gave good defoliation of cotton in a 23 September test. In October tests, defoliation treatments were effective on Pima cotton but upland cotton as difficult to defoliate. Ginstar defoliant was generally as effective as the Dropp + Def treatment at the rates tested.
    • Do Prowl and Treflan Cause Cotton Injury?

      Moffett, Jody; McCloskey, William B.; Husman, Stephen H.; Dixon, Gary L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Two dinitroaniline herbicides, Prowl and Treflan, were tested in field experiments with cotton to determine their differences, if any, in terms of weed control and crop injury potential. Plots treated with the lowest rate of Treflan (0.125 lb a.i./A at one location and 0.25 lb a.i./A at a second location) exhibited reduced weed control in comparison to the other herbicide treatments. Although root inhibition was slight, lateral root growth of cotton was inhibited more by the higher rates of Treflan (0.75 and 1.0 lb a.i./A) than by the higher rates of Prowl (1.0 and 1.25 lb a.i./A). However, differences in weed control and crop injury were not reflected in differences in cotton stand counts, height measurements and yield as there were no significant differences in these parameters between treatments.
    • Dry Matter Accumulation by Upland and Pima Cotton

      Unrah, B. L.; Silvertooth, J. C.; Steger, A. J.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Several investigations of dry matter accumulation by Upland cotton (Gossvpium hirsutum L.) have been conduced, however no investigations of this type have included American Pima cotton (G. barbadense L.). We conducted a study to describe the total dry matter accumulation and partitioning of that dry matter into various plant parts for both Upland and Pima cotton. During the growing seasons of 1990, 1991, and 1992 at two south-central Arizona locations, both Upland (var. DPL 90) and Pima (var. S-6) cotton were grown. Beginning 14 to 20 d after emergence, whole cotton plants were removed and cotton plants were separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction, also included squares, flowers, immature bolls, and burs from mature bolls, Regression analyses was used to model nutrient uptake as a function of both days after planting (DAP) and heat units after planting (HUAP). Regression analyses indicated that HUAP was equally good, and in most cases superior to using DAP to model dry matter accumulation and partitioning within both Upland and Pima cotton. The general patterns of dry matter partitioning for Upland and Pima cotton are similar. However, Upland and Pima differ in the relative amount of dry matter incorporated into reproductive (bur, seed, and lint) and vegetative (leaf and stem) structures. Upland cotton produced 3527 lb /acre more total dry matter than Pima cotton. At the end of this study the vegetative /reproductive ratio for Upland was 83% compared to 70% for Pima. Upland was also more efficient at partitioning lint dry matter within the total dry matter of the reproductive structures. Dry matter incorporated into reproductive structures was 23% lint for Upland, compared to only 14% lint in Pima cotton. In summary, Upland placed more total dry matter into reproductive structures, and of the amount placed into reproductive structures, a greater proportion was incorporated into lint, when compared to Pima cotton.
    • Effect of Foliar Applications of PGRIV on Yield of Upland and Pima Cotton

      Nelson, J. M.; Hart, G. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      The commercial product PGRIV was tested in small plots on cotton at the Maricopa Agricultural Center. Multiple foliar applications of PGRIV had no significant effect on lint yield or fiber properties of DP5415 or Pima S-7 cotton.
    • The Effect of Night Temperature on Cotton Reproductive Development

      Zeiher, Carolyn A.; Brown, Paul W.; Silvertooth, Jeffrey C.; Matumba, Nkonko; Mitton, Nancy; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      A field study was initiated in the summer of 1993 to investigate the effect of increased night temperatures on cotton reproductive development. DPL 5415 was planted on May 10. Treatments consisted of two temperature regimes placed in a completely randomized design with four replications. The two temperature treatments were initiated at first bloom and treatments terminated after 6 weeks. Cotton grown under ambient night temperature served as the control treatments while plants where the infrared radiation balance was modified to increase the nighttime foliage temperature served as the high night temperature treatment. This study showed that increasing the nighttime foliage temperature of cotton reduced vegetative dry matter production, plant height, and fruit retention. The photosynthetic capacity of the two treatments was not significantly different, suggesting that increased respiration at these higher nighttime foliage temperatures may be responsible for the reduction in assimilated carbon which contributed to the poor fruit retention.
    • Effect of Plant Water Status on Defoliation and Yield of Pima Cotton

      Nelson, J. M.; Hart, G. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      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 the yield of Pima cotton. Irrigation termination dates of 3 and 20 September and 8 October were used to achieve different levels of plant water stress at the time defoliants were applied (26 October). A single application of defoliants was not adequate to defoliate the cotton under the conditions of this test. The 3 September irrigation termination date resulted in the highest percentage of defoliation (63 %). CWSI and plant water content (RWC) measurements indicated that the irrigation termination treatments resulted in large differences in plant water stress at defoliation time. There was a significant increase in the percent defoliation as the CWSI values increased from 0.54 to 0.99.
    • The Effects of PIX Application Timing on Upland Cotton Lint Yield and Growth and Development Parameters

      Husman, S. H.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Six commercial scale field studies were conducted from 1991-1993 to further evaluate and predict Upland cotton yield and development responses to PIX application timing as a function of cotton growth and condition. Treatments imposed 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 six 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.
    • Evaluation of a Feedback vs. Scheduled Approach to PIX Application

      Fletcher, D. C.; Silvertooth, J. C.; Norton, E. R.; Unruh, B. L.; Lewis, E. A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Two field experiments were conducted in 1993 in Arizona to compare a scheduled approach (based on stage of growth) versus a feedback approach (based on vegetative status) to mepiquat chloride (PIX™) applications on Upland cotton (Gossypium hirsutum L.). PIX feedback treatments received no PIX applications due to plants lacking vegetative tendencies based upon height:node ratios (HNRs) and established baselines. Scheduled PIX applications ranged from 0.5pt. /acre to 0.75 pt./acre, and were applied at early bloom (approx. 1500 heat units after planting (HUAP), 86/55 °F threshold) and post early bloom (approx. 2000 HUAP). PIX treatments did consistently reduce plant heights compared to an untreated check. Statistically significant differences (P ≤ 0.05) in lint yield were observed among the treatments (feedback vs. scheduled)at the Safford location only. Evidence from these studies do reinforce the use of a feedback approach from the standpoint of conserving inputs and maintaining optimum growth control.
    • Evaluation of Date of Planting on the Yield of Several Upland Varieties at Marana, 1993

      Silvertooth, J. C.; Brown, P. W.; Norton, E. R.; Unrah, B. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      A single field experiment was conducted in 1993 at Marana, Arizona (2,000 ft. elevation) to evaluate the response of three Upland cotton varieties to three dates of planting. Planting dates ranged from as early as 6 April to 11 May. Planting date was a significant effect for all varieties and revealed a substantial drop in yield with delays past 20 April in 1993, which corresponded to 568 heat units (HU, 86/55 °F thresholds) accumulated since 1 January.
    • Evaluation of Trap Crops as a Component of a Community-Wide Pink Bollworm Control Program

      Thacker, Gary W.; Moore, Leon; Ellsworth, Peter C.; Combs, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Trap crops were evaluated as a part of a community -wide pink bollworm (PBW) control program. We measured extraordinarily high numbers of PBW larvae in the trap crops in 1992, which indicated that the trap crops were attracting PBW moths from wide areas. However, we have no direct way of measuring any effect this would have on the main crop. Overall PBW populations were very low in 1993. While PBW numbers drastically declined in the community, this study offers no conclusive evidence as to whether trap crops are an effective component of a community-wide IPM program.