• 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.
    • Influence of Pink Bollworm, Pectinophora Gossypiella, (Saunders) (Lepidoptera : Gelechiidae), Female Age on Oviposition Capacity and Egg Hatchability

      El-Lissy, O.; Al-Beltagy, A.; Antilla, L.; Leggett, J. E.; Silvertooth, Jeff; Arizona Cotton Research and Protection Council, Tempe, AZ; Plant Protection Research Institute, Cairo, Egypt; USDA -ARS- Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Oviposition capability and e 4: hatchability of three laboratory reared strains of pink bollworm, Pectinophora gossvpiella, (Saunders) were evaluated to determine the effect of age on the female reproductive capacity. From comparisons of various female ages in terms of the amount of eggs deposited and the level of ex hatchability, it was concluded that young females (3-6 days old) had the highest potential for oviposition and that their eggs had the highest percentages of hatchability.
    • Initial Post Plant Irrigation Effects on Low Desert Upland Cotton Yields Using Leaf Water Potential Measurements

      Husman, S. H.; Barrot, D. J. Jr.; O'Leary, J. W.; Moore, M.; Wegener, R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Leaf water potential (LWP) measurements using a pressure chamber were used to determine optimum timing of the first irrigation following planting on Upland cotton in 1992 and 1993. 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 studies consisted of three irrigation treatments with four replicates arranged in a randomized complete block design (RCB). Targeted treatment thresholds were 0.15 LWPI (wet), 0.30 LWPI (medium), and 0.45 LWPI (dry). Timing of the first irrigation for the 1992 study occurred at 36, 53, and 63 days after planting. Timing of the 1993 first irrigation occurred at 50, 61, and 77 days after planting for the wet, medium, and dry treatments respectively. There were no significant lint yield differences between irrigation treatments in both 1992 and 1993.
    • 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.
    • Long Staple Cotton Variety Trial, Safford Agricultural Center, 1993

      Clark, L. J.; Carpenter, E. W.; Hart, G. L.; Nelson, J. M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Sixteen long staple cotton varieties (including 4 Pima experimental lines) were tested in a replicated small plot trial on the Safford Agricultural Center. Plots were machine harvested twice to determine yield and percent first pick Small hand samples were taken to determine boll size, percent lint turnout and fiber qualities. Pima S-6 was the highest yielding variety with 1110 pounds per acre of lint. Five of the sixteen varieties yielded over 2 bales per acre. A new variety OA 312 looks particularly promising with yield very close to S-6, fiber quality better than S-6 and an earliness that approaches that of S-7.
    • Methanol Effect on Upland Cotton

      Husman, S. H.; McCloskey, W. B.; Molin, W. T.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      The effects of foliar applied methanol on Upland cotton were measured in a large field study in Phoenix, AZ. An untreated check was compared to weekly applications of 30% methanol, 30% methanol plus 1% Urea and 0.1 % Fe EDTA, and 1% Urea and 0.1% Fe EDTA. Plant growth and development, photosynthesis, transpiration, soil water use and lint yields were measured. There were no differences in any of the measured variables between treatments.
    • Methanol Treatments on Pima and Upland Cotton

      Nelson, J. M.; Nakayama, F. S.; Flint, H. M.; Garcia, R. L.; Hart, G. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      A study was conducted at the University of Arizona Maricopa Agricultural Center, Maricopa, AZ in 1993 to determine the effect of foliar applications of methanol on cotton physiology, growth, yield and whitefly infestation. Six applications of a 30% methanol solution during bloom had no effect on plant height, boll weight, lint yield or earliness of Pima S-7 (Gossvpium barbadense L.) or upland DP5415 (Gossvpium hirsutum L.) cotton. No effect of methanol on photosynthesis or photorespiration was observed. A significant reduction in sweetpotato whitefly nymph population occurred on DP5415 cotton seven weeks after methanol treatment began. This study provided no evidence that methanol can be used to improve cotton production.
    • 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.
    • 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.
    • Numerical and Binomial Sequential Sampling Plans for Adult Bemisia Tabaci in Cotton

      Naranjo, S. E.; Flint, H. M.; Henneberry, T. J.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Fixed-precision numerical and binomial sequential sampling plans are reported for adults of Bemisia tabaci (Strain B) on cotton. Both plans are based on whole leaf sample units from the fifth mainstem node (counted from the terminal). Numerical sampling plans allow for the efficient estimation of adult population density. Numerical sampling stop lines are presented relating the cumulative number of adults counted to the number of leaves examined for two levels of statistical precision. Binomial plans were developed to allow classification of adult population density for pest management decision -making application. These plans were devised for three action threshold levels; 5, 10 or 15 adults per leaf Binomial sampling stop lines are presented relating the cumulative number of infested leaves to the number of leaves examined as an aid for determining the need for population suppression.
    • Nutsedge Control in Cotton Using Norflurazon (Zorial Rapid 80): A Progress Report

      McCloskey, William B.; Dixon, Gary L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      Field experiments were conducted in 1992 and 1993 to determine the crop safety and efficacy of norflurazon applications for control of purple and yellow nutsedge in cotton. Norflurazon was applied preplant-incorporated (PPI) or in two applications, PPI and postemergence (POST) when cotton was 3 to 4" tall. As the PPI norflurazon application rate increased from 0.5 to 0.75, 1.0, and 1.25 lb a.i./A, early season nutsedge control increased from 29 to 49, 58, and 76% of control. Early season weed control declined after about 6 weeks. POST emergence applications of norflurazon prolonged the period of nutsedge control. Data collected 71 and 21 days after the PPI and POST applications, respectively, showed that the 0.5 +1.5, 0.75 +1.25, and 1.0+1.0 lb a.i./A (PPI +POST) treatments resulted in 85, 76, and 73% control of nutsedges. Nutsedge control declined throughout the season with the 0.5 +1.5, 0.75 +1.25, and 1.0+1.0 lb a. i./A split applications all resulting in about 27% control 3 months after the POST applications. PPI rates 1.5 to 2 times the labeled rate for a particular soil type caused cotton injury in several experiments in the 1993 cotton season although no injury was observed in the 1992 season.
    • The Pegasus Rapid Plowdown System: A New Concept in Cotton Tillage

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      This new concept in tillage is to open a deep, temporary slot next to the cotton row and to insert the stalks and/or roots into the slot before the soil falls back in. The Pegasus Rapid Plow Down System is a relatively simple implement which offers good residue burial and reliability. Our limited field test data indicate that this invention requires less energy and field work time than conventional tillage systems.
    • 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.
    • Pima Cotton Genetics

      Percy, R. G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1994-03)
      A feasibility study of short season management in Pima cotton, using short season genotypes, was initiated in 1993. Four short season genotypes, a full season check, and a short season check were evaluated in replicated tests under short season and full season regimes. In this first preliminary year of data, no significant yield loss could be attributed to management regime or to earliness of genotypes. Three of the putative early maturing genotypes exceeded the full season Pima S-7 check in yield. Results were contrary to expectations. The short season test is planned for repeat in 1994. An investigation of a virescent mutant discovered in 1990 (CM-1-90) was conducted in 1991, 1992, and 1993. Crosses of the mutant to Pima S-6 to determine inheritance, and to various virescent mutants to determine allelism produced results which were anamolous to normal, nuclear inheritance. Reciprocal crosses to PS-6 and to various virescent mutants confirmed that the new mutant was cytoplasmicaly inherited.