• 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.
    • 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.
    • Plant Population Evaluation for Upland Cotton

      Silvertooth, J. C.; Norton, E. R.; Stedman, S. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
    • Nitrogen, Phosphorus, and Potassium Uptake by Upland and Pima Cotton

      Unruh, 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 nitrogen (N), phosphorus (P), and potassium (K) uptake by Upland cotton (Gossypium 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 N, P, and K uptake and the partitioning of each nutrient 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. The appropriate analyses for total N, P, and K were determined on each fraction (except lint). 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 total nutrient uptake and partitioning within both Upland and Pima cotton. In every case there was close agreement between the predicted and actual total nutrient uptake. For Upland cotton the actual total N, P, and K uptake was 199, 29, and 250 kg ha⁻¹ and the predicted total N, P, and K uptake was 199, 29, and 255 kg ha⁻¹, respectively. For Pima cotton the actual total N, P, and K uptake was 196, 29, and 215 kg ha⁻¹ and the predicted was 210, 29, and 229 kg ha⁻¹, respectively. The pattern of nutrient partitioning in Upland cotton were similar to the findings of others and Pima showed the same general patterns of partitioning as Upland cotton. Seeds were a major sink of nutrients. Nutrient uptake in seeds resulted in decreasing uptake in leaves and stems. Presumably, due to mobilization of nutrients from those parts to the seeds during seed development. The nutrient requirements to produce 100 kg lint ha' for Upland cotton was 15, 2.2, and 19 kg ha⁻¹ for N, P, and K, respectively and was 20, 3.0, and 22 kg ha⁻¹, respectively for Pima cotton.
    • Novel Pyrethroid Combinations for Control of Sweetpotato Whitefly and Their Impact on Lygus

      Ellsworth, P. C.; Meade, D. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Combinations of two insecticides, often a pyrethroid with an organophosphate, have been used more successfully in sweetpotato whitefly (SPWF) control programs rather than single insecticides when SPWF populations are chronically high. Ten combinations of various insecticides were compared for their effectiveness against all SPWF stages. Applications were by ground, broadcast over -the -top of plots 12 rows x 40 ft on five application dates. Three sampling methods were used: leaf turns and sweeps for adult counts, and microscopic leaf counts for immature stages. Danitol® +Orthene® emerged as the most consistently effective combination on all SPWF stages when compared to the untreated plots. Over all dates and SPWF life stages, the combinations were ranked according to the following order of descending efficacy: Danitol + Orthene 5 Danitol + Lorsban® Karate® + Penncap -M® = Scout Xtra® + Orthene = Asana® + Curacron® = Asana + Orthene < Asana + Phaser® = Scout + Phaser = Asana + Lorsban = Asana + Vydate® < untreated check. Yields were also affected by the combinations, but attributed to SPWF and Lygus suppression. Orthene treatment combinations yielded consistently greater than other entries and was likely due to superior Lygus control and at least average SPWF control. The Asana + Vydate was ranked among the best in Lygus control but low in SPWF control, while Karate + Penncap, Danitol + Lorsban, and Asana + Curacron were ranked high in SPWF control but low in Lygus control. The remaining treatments were more or less intermediate in SPWF and Lygus control. Rankings of these combinations for Lygus control were in the following order of descending efficacy: Asana + Vydate = Scout + Orthene = Asana + Orthene = Danitol + Orthene < Scout + Phaser = Danitol + Lorsban = Karate + Penncap < Asana + Curacron < Asana + Phaser = Asana + Lorsban < untreated check.
    • Irrigation Efficiencies and Lint Yields of Upland Cotton Grown at the Maricopa Agricultural Center, 1993

      Sheedy, Mike; Watson, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      The computer program AZSCHED, with weather data obtained from AZMET, was used to schedule irrigations for a yield trial of early season Upland Cotton (DPL 20) at the Maricopa Agricultural Center. Cotton lint yields were compared between plots from five treatments involving five irrigation efficiencies (50 %, 65 %, 75 %, 90% and 110 %). As in previous years, a potassium bromide tracer was applied to select areas in each plot to monitor the movement of water and nitrates down the soil profile. The total amount of fertilizer as nitrogen applied in two split applications and sidedressed was 100 #/a. The total amount of water applied to the plots ranged from 42.7" for 50% to 26.6" for 110% (deficit) irrigation efficiency. The plots were harvested on October 5, 1993. There was a significant difference in lint yield between the irrigation efficiency treatments. The 50% irrigation efficiency treatment produced 1190 # lint /acre while the 110% efficiency produced 883 # lint /acre.
    • Potential for Pink Bollworm Control with Entomopathogenic Nematodes

      Lindegren, J. E.; Henneberry, T. J.; Raulston, J. R.; Forlow Jech, L. J.; Valero, K. A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      The susceptibility of late instar pink bollworm (PBW), Pectinophora gosspiella (Saunders), larvae to two species of Steinemema was evaluated in small scale field tests in spring and summer of 1993. In the spring PBW mortality at 15 infective juveniles /cm² for S. carpocapsae and S. riobravis was 87 and 89 %, respectively. In midsummer, mortalities with S. riobravis were significantly greater than with S. carpocapsae at the four concentrations tested. A simple method was developed for small scale field testing and efficacy monitoring for PBW and other soil associated insects.
    • Physiological Response of Cotton to Terminal Damage

      Unruh, B. L.; Silvertooth, J. C.; Hanline-Boerum, T. R.; Marlow, B. M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      The terminal of a cotton (Gossypium spp.) plant controls the growth of lower vegetative branches through the production of hormones. If the terminal is damaged then the lower vegetative branches will begin to grow and produce new mainstems. The objective of this study was to determine what delays, if any, are caused by damage to the terminal meristem. Three identical experiments (differing only by their planting date) were conducted in the greenhouse in which Upland (G. hirsutum L., var. DPL 5415) cotton was planted in 24 pots and allowed to grow until the majority of the plants reached the four true -leaf stage. At that point half of the plants had their terminals removed. Twice weekly series of plant measurements were recorded for each plant in the study. Measurements taken included the number of mainstem nodes, plant height, node of the first fruiting branch (FFB), days after terminal removal (DATR) until the appearance of the FFB, node of the first bloom, and DATR until the appearance of the first bloom were recorded. Removal of the terminal significantly increased the node of the FFB, the node of the first bloom, and the occurrence of each of these by 7 to 8 days. Regression analysis was used to model plant height and the accumulation of mainstem nodes as a function of DATR. Results showed that plants with terminals removed did reach the same height as the control group. However, the plants with their terminals removed never accumulated as many mainstem nodes as their counterparts in the control group.
    • Seasonal Distribution of Cotton Leafperforator: Pheromone Dispenser Persistence and Effect of Trap Height on Moth Catches in Pheromone Baited Traps

      Leggett, J. E.; Henneberry, T. J.; White, R. D.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      The cotton leafperforator (CLP) Bucculatrix thurberiella Busck. is a sporadic pest in cotton fields of southwest desert area. The cotton leafperforator sex pheromone was identified and synthesized by Hall et al. (1992), thus providing a sensitive method for detecting CLP moths. Tests were conducted in 1992 and 1993 to determine the effective life of CLP polyethylene pheromone dispensers, correlate CLP male moth catches to cotton field infestations, determine the seasonal distribution, and effect of trap height on moth catches. The polyethylene pheromone dispensers were effective for about 4 weeks. The best correlation coefficients for 1993 data, were obtained by comparing CLP moth catches per night to main stem leaf damage at 6 node position from top of plants at field edges. Horseshoe stage CLP per leaf and trap catches had the highest correlation coefficient, r= 0.78. There was more than twice as much CLP damage to leaves at field edges when compared to leaves 10 m into the field. The first CLP moth capture occurred in early to late July and increased rapidly each year in August to 100 to 200 per trap night, but was variable in September, with a high of 300 and a low of 9 per trap night. CLP- baited delta traps placed 0.3 m above ground caught more moths than traps placed at greater heights from 11 to 21 August.
    • Use of Leaf Water Potentials to Determine Timing of Initial Post-Plant Irrigation

      Steger, A. J.; Silvertooth, J. C.; Brown, P. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Presumably, from a physiological standpoint, early season water stress should be avoided to ensure early fruit initiation, good fruit retention, and optimum yield potential of cotton (Gossypium spp.). This study was conducted to determine the optimum timing of the initial post plant irrigation and the long term effect of postponement on subsequent plant growth patterns, fruit retention, and yield. A short - season Upland variety, (G. hirsutum L.), DPL 20, was planted on 19 April in Marana, AZ, elevation 1970 ft. , on a Pima clay loam (Typic Torrifluvent) soil. Plots (experimental units) consisted of eight 40 in. rows and extended the full length of the irrigation run (600 ft.). Experimental design was a randomized complete block with four replications. Initial post - plant irrigations, designated T1 , 72, and T3, were applied when the midday leaf water potential (ψ) of the uppermost, fully- developed leaf reached -15, -19, and -23 bars, respectively. All treatments received the same irrigation regime following the initial post plant irrigation. Basic plant measurements were taken weekly from each experimental unit. These included plant height, number of mainstem nodes, location of first fruiting branch, fruit retention, number of nodes above the uppermost white bloom, bloom count within a 166 ft² area, and percent canopy cover. Soil -water data at seven 25 cm depth increments was collected from a total of 36 access tubes located within the field study, with three tubes per plot. Lint yields (lb. lint /acre) were 1112, 1095, and 977 for T1 , 72, and T3, respectively. Yields were significantly lower when the initial post plant irrigation was applied after ψ, dropped below -19 bars, confirming the results of a previous study conducted in 1992. Throughout the growing season, height - node ratios (HNR) of T1 and 72 plants were at or above the upper threshold established for DPL 20, while T3 HNR remained close to the expected baseline. Fruit retention was low for all three treatments due to season -long insect pressure from lygus bug. The low fruit retention data reflects the effects of high HNR. Future work will include efforts to separate changes in ψ due to day-to-day climatic variations from those caused by soil -water depletion. A second objective will be to incorporate the data obtained from the neutron moisture meter probe into the study results in an effort to better describe the complete soil-plant-atmosphere continuum as affected by the various treatment regimes employed in this study.
    • 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.
    • 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.
    • 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.
    • Pima Regional Variety Test Maricopa Agricultural Center, 1993

      Hart, G.; Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Twelve Pima varieties and experimental strains were grown in a replicated trial at the Maricopa Agricultural Center. Lint yield, boll size, lint %, gin turnout %, plant population and fiber property data are presented in this report.
    • Action Thresholds for Whiteflies in Arizona

      Ellsworth, Peter C.; Meade, Donna L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Three field tests were set -up for evaluation of action threshold levels for sweetpotato whitefly control with two different chemical combinations. The thresholds used to initiate treatments were ca. 1, 10, and 25 adult whiteflies per leaf designated as "early ", "moderate ", or "late ". Immatures were present during these treatment initiation points at the rate of ca. 5 nymphs and ca. 10 eggs per sq.in. in the 'early' plots, 15.3 nymphs and 39.1 eggs per sq.in. in the 'moderate' plots, and 52.1 nymphs and 299.3 eggs per sq.in. in the 'late' plots. The insecticides used included a pyrethroid combination [Danitol® (.1 lb a.i/A) + Orthene® (.5)] and a non-pyrethroid combination [endosulfan(.75) + Ovasyn® (.25)1 Applications were by ground, broadcast, over-the-top, at 20 GPA. Populations were monitored as whitefly adults (leaf turns & net sweeps) and nymphs and eggs (leaf counts). Once applications were triggered, they continued ca. weekly. The early threshold required seven applications, starting 10 July, and produced yields (4038.8 lbs seed cotton/A) which were 2 or 3 times larger than the untreated check (1589.3 lbs seed cotton/A). Lint or leaf stickiness was not apparent; however, 2 or 3 sprays were required before any significant differences in whitefly populations could be found. Whitefly numbers were lowered significantly in both insecticide regimens, with somewhat lower numbers present in the pyrethroid treated plots. The late threshold was sprayed only twice, starting 12 August, and yielded no more cotton (1719.2 lbs seed cotton/A) than the untreated check (1395.0 lbs seed cotton/A). Lint and leaf surfaces were covered in stickiness and sooty mold. Whitefly populations were excessive and led to premature cut -out and poor fruit retention. The moderate threshold (10 adults per leaf) received five applications, starting 22 July, and produced high yielding and high quality cotton (3462.2 lbs seed cotton/A). Some stickiness and sooty mold growth was observable only on the lowest leaves. This was a result of limited honeydew production prior to the threshold and well before any boll opening. Lygus populations were extremely high and caused large differences in yields which favored the pyrethroid combination slightly and the earliest threshold significantly. Given commercial farm control realities (e.g., delays in sampling or application, differences in coverage or application, variable efficacy), the ideal threshold for initiation of treatments is likely between 1 and 10 adults per leaf.
    • Potassium Fertilization of Upland and Pima Cotton

      Unruh, B. L.; Silvertooth, J. C.; Galadima, A.; Clark, L. J.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      In a continuing effort to assess the agronomic necessity of potassium (K) fertilization in Arizona cotton (Gossypium spp.) production, one new and two on-going (Maricopa and Safford Ag. Centers), K fertility studies were conducted in 1993. They included locations ranging from western (Yuma) to eastern (Safford) Arizona, with both Upland (G. hirsutum L.) and American Pima (G. barbadense L.) cotton, using soil and foliar applications of K. The results indicated that there was no response to the added K at any of the locations by either Upland or Pima cotton.
    • Nitrogen Management Experiments for Upland and Pima Cotton, 1993

      Silvertooth, J. C.; Norton, E. R.; Unruh, B. L.; Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Two field experiments were conducted in Arizona in 1993 at two locations (Maricopa and Safford). Both experiments have been conducted for five consecutive seasons, with consistent plot locations. 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 have been consistently evident in crop maturity and its relationship to lint yields.
    • Preliminary Field Evaluation of an Insect Growth Regulator, Buprofezin, for Control of the Sweetpotato Whitefly, Bemisia Tabaci

      Ellsworth, P. C.; Meade, D. L.; Odom, Phillip; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Two rates of buprofezin and a combination, buprofezin + endosulfan, were compared against Ovasyn® and the standard pyrethroid combination Danitol® + Orthene®. Targeted pests were all stages of the sweetpotato whitefly (SPWF). Danitol + Orthene was the most effective treatment against all SPWF stages. All buprofezin treatments, including the buprofezin + endosulfan combination, were moderately effective against all SPWF stages relative to the untreated check, while Ovasyn had control levels similar to the untreated check. Danitol + Orthene had the highest yield at 4030.2 lbs seed cotton/A, and buprofezin + endosulfan had the second highest yield, 2172 lbs/A. All other treatments yielded amounts similar to the untreated check, 863.0 lbs/A. Effects of these control practices on beneficial and other non- target arthropods have not yet been analyzed. Lygus populations were extreme in this test and favored the Danitol + Orthene treatment over the SPWF -specific buprofezin treatments.
    • Practical Uses of Crop Monitoring for Arizona Cotton

      Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
    • Upland Regional Cotton Variety Test at the Maricopa Agricultural Center, 1993

      Hart, G.; Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Thirty-six upland cotton varieties were grown in a replicated trial at the Maricopa Agricultural Center as part of the National Cotton Variety Testing Program. Lint yield, boll size, lint percent, gin turnout percent, plant population and fiber property data are presented in this report.