• Contrasts of Three Insecticides Resistance Monitoring Methods for Whitefly

      Simmons, A. L.; Dennehy, T. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Three resistance monitoring methods were tested to evaluate their relative reliability, discriminating ability, convenience, and practicality for monitoring insecticide resistance in Arizona whiteflies. Adult whiteflies were collected from the field and tested in the laboratory with three methods: leaf disk, sticky trap, and vial. Each method was evaluated against two populations divergent in susceptibility using a mixture of Danitol® + Orthene® and two single chemicals, Thiodan® and Danitol®. The Yuma population was relatively susceptible and the Gila River Basin population highly resistant. Correlations of field efficacy and leaf disk bioassays were conducted with the Yuma population and a comparatively resistant Maricopa population. At each location egg, immature, and adult whitefly densities were monitored before and after Danitol® + Orthene® treatments and resistance estimates were also monitored in the populations using leaf disk bioassays. Our results illustrated that the leaf disk method had the greatest discriminating ability between susceptible and resistant populations. The results also indicated that the vial method was the most practical, and that the sticky trap method was good at discriminating between populations that have large differences in susceptibility. The field efficacy trials indicated results from leaf disk assays reflected what had occurred in the field.
    • Cotton Defoliation Evaluations, 1995

      Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      A single field experiment was conducted near Coolidge, AZ in 1995 to evaluate the effectiveness of a number of defoliation treatments on Upland cotton (var. DPL 5415). All treatments consisted of materials commercially available in Arizona, and each showed promise in terms of overall effectiveness. Results do provide reinforcement for current defoliation guidelines for Arizona which recommend using low rates (relative to the label ranges) under warm weather conditions, and increasing rates as temperatures cool.
    • Cotton Growth and Development Patterns

      Silvertooth, J. C.; Norton, E. R.; Brown, P. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Summaries of cotton crop phenology, as a function of heat units (HU, 86/55°F limits) have been developed across a wide range of production conditions in Arizona. Basic phenological events such as the occurrence of pinhead squares, squares susceptible to pink bollworm, and first bloom are described in terms of HU accumulations since planting (HUAP). Fruit retention guidelines and height: node ratios, which measure a crop's vegetative /reproductive balance, are developed as a function of HUAP. Similarly, the rate of canopy closure is described in terms of HUAP. The use of the number of nodes above the top white bloom to the terminal (NAWB) is developed as a measure of a crops progression towards cut-out. Also, the expected ranges of HU's accumulated since planting that are required to accomplish crop cut-out are shown for Upland and Pima cotton.
    • Cotton Irrigation Scheduling Trial on Pima and Upland Cotton Using AZSCHED, Safford Agricultural Center, 1995

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Irrigation scheduling is an important practice in cotton cultivation in the and southwest. AZSCHED irrigation scheduling software was used as a tool to schedule irrigation and then evaluate the soil water depletion levels over irrigation treatments with DP 90 and Pima S6. Lint yields were compared and irrigation costs were calculated for the various treatments. The highest yields and income levels came from applying irrigation when the soil depletion levels reached 40%.
    • Cultural Control and Pink Bollworm Populations

      Chu, C. C.; Henneberry, T. J.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory, Phoenix, Arizona 85040-8830 (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      A cotton management program in the Imperial Valley, CA was designed to reduce pink bollworm, Pectinophora gossypiella (Saunders), populations. The program established I March as the earliest planting date, 1 September for defoliant or plant growth regulator application and 1 November for cotton stalk destruction and plowdown. In-season gossyplure-baited pink bollworm male moth activity monitoring and immature green cotton boll inspections for larval infestation were encouraged as decision making aids to determine the need for additional control action. Male pink bollworm moth catches in gossyplure-baited Lingren and delta sticky traps were significantly reduced each year from 1990 to 1994 following the initiation of the management program in 1989. Fewer larvae per cotton boll occurred in the years from 1990 to 1992. Fiber quality of commercial cotton sampled was also improved from 1989 to 1994, as compared to the 1984 to 1988 average. Cotton production, in general, was reduced during 1989 to 1994 in areas surrounding Imperial Valley and may have contributed partially to reduced populations in Imperial Valley.
    • Defoliation of Pima and Upland Cotton at the Safford Agricultural Center, 1995

      Clark, L. J.; Carpenter, E. W.; Odom, P. N.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Twelve defoliation treatments were applied to Pima and upland cotton to compare the treatment effects on percent defoliation of the plants, percent first pick values, percent gin trash and any effects they might have on fiber qualities. All of the treatments were beneficial compared to the untreated check, but differences between treatments were small.
    • Defoliation Tests with Ginstar at the Maricopa Agricultural Center in 1995

      Nelson, J. M.; Hart, G. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Defoliation tests were conducted on upland cotton at the Maricopa Agricultural Center to evaluate rates of Ginstar and tank mixes of Ginstar with Def, Prep, and spray adjuvants. In September when temperatures were high, good defoliation was obtained 14 days after treatment using Ginstar at 0.094 lb. a. i./acre. As temperatures cooled in early October, a higher rate of Ginstar was necessary to achieve defoliation. Under very cool temperatures in late October and early November, the tank mix of Ginstar + Def generally improved defoliation over Ginstar used alone. Several adjuvants appeared to improve the effectiveness of Ginstar when temperatures were cool.
    • Development of a Yield Projection Technique for Arizona Cotton

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      A series of boll measurements were taken at several locations across the state in 1995 in an attempt to develop a yield prediction model. Measurements were taken out of two strip plot variety trials at the University of Arizona Maricopa Agricultural Center and in the Coolidge area, and also out of two commercial fields in Buckeye and Paloma Ranch over a period of approximately 2 months from peak bloom through cut-out. Data analysis revealed a best fit model that included seedcotton yield as a function of boll count, boll size, boll diameter, and heat units accumulated after planting (HUAP). A series of open boll counts were also taken from over 120 experimental units across the state within one week of harvest. The data revealed strongest relationships between final open boll counts and yield.
    • Differential Tolerance of Cotton Cultivars to Prometryn

      Molin, William T.; Khan, Rehana A.; Pasquinelli, Michael; Galadima, Abraham; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      The tolerance of cotton cultivars to the herbicide prometryn was determined in greenhouse tests. Prometryn was applied preemergence from 0.3 to 12.0 lbs. a.i./A and postemergence from 1.2 to 12.0 lbs. a.i./A. Upland cultivars were very susceptible to injury from prometryn applied preemergence; whereas Pima S-6, Pima S-7, and Acala 1517-75 were tolerant. Postemergence treatments of prometryn applied two weeks after planting were less injurious to Upland cultivars than preemergence treatments, however, differential tolerance between, Pima and Upland cultivars was evident at the high rates of application.
    • Distribution and Genetic Variability of Whitefly-Transmitted Geminiviruses of Cotton

      Brown, J. K.; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Whitefly-transmitted geminiviruses (subgroup III, Geminiviridae) are emerging viral pathogens of cotton, worldwide. Virtually nothing is known about the genetic variability, biological characteristics, or the molecular epidemiology of these new virus pathogens of cotton. The core region (550bp) of the geminiviral coat protein gene was examined as a potentially informative molecular marker by which to identify and track the global distribution of WFT geminiviruses of cotton. This is an essential step toward assessing the risks that emerging viruses pose to cotton production efforts. Preliminary analyses of geminivirus isolates from North America, Central America and the Caribbean Basin, and Sudan indicate that the core region of the coat protein gene permits predictions about relationships between virus isolates from cotton, based on subgeographical and major geographical origins, and has potential for distinguishing between geminiviral quasi-species and virus strains, thereof Through these efforts, a database of geminivirus coat protein gene sequences has been established to permit identification of additional isolates from cotton, and to facilitate the tracking of WFT geminiviruses for molecular epidemiological and subsequent risk assessment objectives. Using the latter information, it will become possible to identify the most important geminiviruses against which disease resistance efforts should be directed. Further, the availability of a broad suite of cotton geminivirus isolates from both Eastern and Western Hemispheres will permit assessment of cotton germplasm and/or genetically engineered lines for virus-specific and/or broad spectrum disease resistance for the first time.
    • Effect of Norflurazon (Zorial Rapid 80®) Mixed with Pendimethalin (Prowl®) and Prometryn (Caparol®) on Cotton Stand Establishment and Yield

      McCloskey, William B.; Dixon, Gary L.; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      The effect on cotton stand establishment and seed cotton yield of various rates of norflurazon applied in combination with pendimethalin or both pendimethalin and prometryn was determined in field studies conducted at the Maricopa Agricultural Center in 1994 and 1995 in a sandy loam soil. Cotton stand counts were highest when only pendimethalin was applied or when no herbicide was used. Tank mixing prometryn with pendimethalin did not significantly reduce plant populations. Tank mixing increasing amounts of norflurazon with pendimethalin resulted in decreasing plant populations in both the wet and the dry plant experiments. Tank mixing increasing rates of norflurazon with both pendimethalin and prometryn caused a similar decline in plant populations in both the wet and the dry plant experiments. The symptoms of dying cotton seedlings and the stand count data indicated that notflurazon was the component of the tank mixtures that caused seedling mortality. The effect of the herbicide treatments on seed cotton yields was much less than on stand counts, but the same trends discussed above were evident. However, at the label rate for norflurazon in coarse textured soils, 0.5 lb a. i./A, seed cotton yields were not significantly reduced. The smaller effect of the herbicide treatments on seed cotton yields was due to the bush type nature of DPL 5415 and increased growth of surviving plants when plant populations were reduced. The data indicates that yield losses were not significant unless plant populations were reduced below about 20,000 to 25,000 plants /A.
    • Effects of Combinations of Accelerate and Other Defoliants on Defoliation of Upland Cotton

      Nelson, J. M.; Silvertooth, Jeff; Maricopa Agricultural Center (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Field studies were conducted on upland cotton at the Maricopa Agricultural Center to evaluate the effectiveness of Accelerate when used in combination with other defoliants. In a September test, good defoliation was obtained in seven days using Ginstar or Dropp + Def + Accelerate and in 14 days using Accelerate + Prep. In October, under cooler conditions, no treatment provided acceptable defoliation in 14 days. In both tests, Ginstar used alone resulted in higher leaf drop percentages than Ginstar + Accelerate.
    • Effects of Silverleaf Whiteflies on Sticky Cotton and Cotton Yields in Arizona

      Henneberry, T. J.; Forlow Jech, Lynn; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory, Phoenix, Arizona 85040 -8830 (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Silverleaf whitey, Bemisia argentifolii Bellows and Perring, adults and nymphs were significantly reduced season -long in cotton plots treated with fenpropathrin plus acephate on 3 occasions (15 July, 2 August and 29 August). Thermodetector sticky cotton ratings were significantly reduced in insecticide-treated plots compared with untreated plots. Heavy rains reduced cotton stickiness in all plots.
    • Evaluation of a Feedback Approach to Nitrogen and Pix Application

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      A single field experiment was conducted in 1995 at Maricopa, AZ to compare a scheduled approach (based on stage of growth) versus a feedback approach (based on vegetative status) to both nitrogen (N) and mepiquat chloride (PIX™) applications on Upland cotton (Gossypium hirsutum L.). PIX feedback treatments were based upon fruit retention (FR) levels and height to node ratios (HNRs) according to established baselines. Scheduled and feedback PIX applications were made for a total of 1.0 pt./acre over two applications, with the scheduled treatments-taking place earlier in the fruiting cycle (early and peak bloom). Feedback PIX treatments began with a single 0.5 pt. /acre application near peak bloom (approx. 2200 heat units after planting (HUAP), 86/55 °F threshold) and followed with a second 0.5 pt. /acre application in late bloom. Scheduled applications of fertilizer N totaled 200 lbs. N/acre from three applications and feedback N treatments received a total of 100 lbs. N/acre from two applications. Treatments consisted of all combinations of scheduled or feedback applications of both N and FIX. The highest lint yields were from a treatment receiving feedback N and FIX, but all treatment yields were not significantly different (P ≥ 0.05) from one another. From a practical (economic) standpoint, however, these treatments were different in terms of the differences of fertilizer N and the timing of the PIX applications required to produce comparable yields. Results from 1995 are consistent with 1993 and 1994 results from the same study.
    • Evaluation of Irrigation Termination Management on Yield of Upland Cotton, 1995

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      A single field study was conducted in 1995 at the Maricopa Agricultural Center (1100 ft. elevation) to evaluate the effects of three dates of irrigation termination on yield a common Upland cotton variety (DPL 5415). Planting date was 3 April (469 HU /Jan 1 86/55° F thresholds). Following difficult establishment, crop vigor was generally low all season, with a relatively strong level of fruit retention. Three dates of irrigation termination an -1T3) were imposed based upon crop development into cut -out, with IT1 (21 August) set such that bolls set at the end of the first fruiting cycle would not be water stressed and could be fully matured. The third termination (IT3) date was 22 September, which was staged so that soil moisture would be sufficient for development of bolls set up through the first week of September. The second irrigation termination (IT2, 1 September) was intermediate to IT1 and IT3. Lint yield results revealed a 139 lb. lint/acre difference between IT1 and IT3, which was statistically significant (P < 0.05).
    • Evaluation of Soil Conditioners and Water Treatments for Cotton Production Systems

      Silvertooth, J. C.; Sanchez, C. A.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Advanced technologies to produce synthetic polymers such as polyacrylamide (PAM, and polymaleic anhydride (PMA) have produced products which may be economically feasible alternatives to traditional treatments such as gypsum in the desert Southwest. In 1995 a single field study was conducted at Paloma Ranch, west of Gila Bend in Maricopa County Arizona Upland Nucoton 35, DPL' was dry planted and watered -up on 10 and 11 April. Treatments consisted of various rates and times of applications of Sper Sal™, which included a check (no Sper Sal), 1 and 2 qts. /acre with the water-up irrigation; 1 and 2 qts./acre with a mid - season irrigation; and 1 qt. /acre mid-season following 1 or 2 qts./acre with the water -up irrigation. No differences among treatments were detected among any treatments in terms of plant growth and development or final lint yields. There were no early-season differences in soil crusting among the various soil amendment treatments in 1995, as opposed to 1994 when a severe rain occurred immediately following planting.
    • Fenoxycarb, Pymetrozine (C G A-215944), and Fenpropathrin/Acephate: Rotations for Silverleaf Whitefly Control in Upland Cotton in Central America

      Akey, D. H.; Henneberry, T. J.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory, 4135 East Broadway, Phoenix, Arizona 85040 -8830 (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Trials (0.01 ac plots) with fenoxycarb ( Fenoxycarb 40 W P, 0.0621b. ai /ac), pymetrozine (CGA 215944, Fulfill™ 50 W P, 0.094 lb. ai/ac), pymetrozine /fenoxycarb, (SterlingTM ), and fenpropathrin (DanitolTM 2.4 E C, 0.20 lb. or 0.10 lb. ai/ac) /acephate (OrtheneTM 90 S, 0.5 or 0.25 lb. ai /ac) were made against silverleaf whitefly, Bemisiq grgentifolii Bellows and Perring, at UA, Maricopa Agric. Ctr. Six applications (plus adjuvant Kinetic) were applied on 9 treatments. Ten treatments (embedded control included) were in a double tier complete random block design and there was I adjacent, 1.5 ac control block (treatment 11). Eggs and large nymphs were sampled weekly post application to determine efficacy; reported as % reduction from block control. Rotation schemes were: 1) 3 pymetrozine /fenoxycarb, then 3 fenpropathrin/acephate applications, 2) 3 pymetrozine 2 /3rate /fenoxycarb full rate, then 3 fenpropathrin /acephate applications, 3) fenoxycarb 6 applications, 4) pymetrozine 6 applications, 5) 3 fenpropathrin /acephate, then 3 pymetrozine /fenoxycarb applications, 6) 3 fenpropathrin /acephate, then 3 pymetrozine /fenoxycarb, 7) fenpropathrin /acephate at full, l/2, full, then 3-1/2 rate applications, 8) 2 pymetrozine /fenoxycarb, 2 fenpropathrin /acephate, 1 pymetrozine /fenoxycarb, and 1 last fenpropathrin /acephate application, 9) 2 fenpropathrin /acephate, 2 pymetrozine /fenoxycarb, 1fenpropathrin/acephate, and 1 last pymetrozine /fenoxycarb application, 10) embedded control, and 11) block control. Egg % reductions for season means ranged from 93-99% for combinations and rotations of them. Last % season analyses showed reductions from 95-99 %. Pymetrozine had a 98% reduction andfenpropathrin /acephate had 98 % egg reduction. Nymphal reduction for season means ranged from 80-95% for combinations and rotations of them. Last % season analyses, showed % reductions from 91-98 %. Pymetrozine had 92% reduction and fenpropathrin /acephate had 92% reduction of nymphs (season). These studies showed that pymetrozine, pymetrozine /fenoxycarb, fenpropathrin/acephate combinations and rotations provided excellent control of silverleaf whitefly immatures.
    • How the Quick Hitch Guidance Systems Work and Their Practical Applications

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      This article explains the operation of the two types of quick hitch guidance systems on the market. Techniques for farming with precision guidance are offered.
    • How to Mechanically Remove Weeds from the Row

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      This article offers practical advice on in-row weeding techniques and tooling setups.
    • Irrigation Efficiencies and Lint Yields of Upland Cotton Grown at the Maricopa Agricultural Center, 1995

      Sheedy, Mike; Watson, Mike; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      A field trial was conducted at the Maricopa Agricultural Center to observe the effects of four irrigation efficiencies (65%, 75%, 85%, and 95%) on the lint yield produced from two upland cotton varieties (DP 5409 and SG 125). Nitrogen requirements for the crop were determined using pre-season soil samples and in-season petiole samples in conjuction with crop monitoring data collected at weekly intervals. AZSCHED was used as a guide to the irrigation timing and amount of water applied during the season. The actual irrigation efficiencies obtained were less than what was targeted. The end season results were 59, 62, 62, and 68 %, respectively. This is due in part to the inherent inefficiency of irrigations in the early season. This year there was a lint yield response to the different irrigation efficiencies, but no difference in yield between the two varieties. Lint yields were significantly lower in the 95 % irrigation efficiency plots. Lint Yields ranged from 1058 and 1109 # lint/acre (DP5409 and SG125 at 95 %) to 1358 and 1353 # lint/acre (SG 125 and DP5409 at the 85 % irrigation efficiency).