• 1995 Seed Treatment Evaluations

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Cottonseed was treated with several fungicide treatments in an effort to protect the seed and seedling from disease. Seed germination and vigor was evaluated in two Arizona locations; Maricopa and Marana. Stand counts were taken on two separate dates after emergence at both Maricopa and Marana and percent emergence was calculated. Significant differences in percent emergence due to treatment were observed in both sample dates at Marana. Results at Maricopa were not statistically significant but similar trends to those at Marana were observed with treatment number 6 (no treatment) having the lowest percent emergence and treatment number 2 (combination of Nu-Flow ND and Apron TL) having the highest emergence.
    • 1995 Weather Conditions

      Brown, P.; Russell, B.; Machibya, T.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      The 1995 cotton season proved to be one of the most challenging in marry years. Cold, dry spring weather delayed planting and forced many growers to replant a significant portion of their crop. The late crop then ran into extreme summer heat in July and August and very high August humidity. Daytime temperatures in excess of 120°F were reported in the low deserts in July and many locations reported extended periods with daytime temperatures above 1107. Poor fruit retention was a common grower observation as the summer heat continued The saving grace for 1995 proved to be warm and dry fall weather which assisted late season development and harvest operations.
    • The 1996 Arizona Cotton Advisory Program

      Brown, P.; Rusell, B.; Silvertooth, J.; Ellsworth, P.; Stedman, S.; Thacker, G.; Husman, S.; Cluff, R.; Howell, D.; Winans, S.; Grumbles, R.; Knowles, T.; Dunn, D.; Schneider, M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Arizona Cooperative Extension generates and distributes weather -based Planting Date and Cotton Development Advisories for 14 cotton production areas (Marana, Laveen, Paloma, Litchfield Pk., Pinal Co., Parker, Mohave Valley, Queen Creek, Safford, Yuma Valley, Aguila, Cochise Co., Greenlee Co. and Harquahala). Planting Date Advisories are distributed from mid -February through the end of April and stress 1) planting cotton varieties according to heat unit accumulations rather than calendar date and 2) the importance of soil temperature to good germination. Cotton Development Advisories are distributed from early May through mid - September and provide updates on crop development, insects, weather and agronomy. The Cotton Advisory Program will continue in 1996 and growers may obtain advisories by mail or fax from the local county extension office, and by computer from AZMET or the University of Arizona College of Agriculture World Wide Web Page. Major program changes planned for 1996 include 1) adjusting the Crop Development Advisories to reflect the revised legal first planting dates in low elevation production areas and 2) the addition of an advisory for Harquahala.
    • Arizona Upland Cotton Variety Testing Program

      Silvertooth, J.; Norton, R.; Clark, L.; Husman, S.; Cluff, R.; Stedman, S.; Thacker, G.; Knowles, T.; Winans, W.; Grumbles, R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Eleven field experiments were conducted in many of the cotton growing areas of Arizona in 1995 for the purpose of evaluating Upland cotton varieties in terms of adaptability and performance. Seven commercial cottonseed companies participated in the program. Two varieties were submitted from each company at each location. Experiments were conducted on grower - cooperator fields in each case. Locations used in the program spanned the range of conditions common to cotton producing areas of the state from about 150 ft. to 4, 000 ft. elevation. Results indicated a broad range of adaptability and competitiveness on the part of each of the participating companies and their representative varieties. The 1995 season offered some extremes in terms of weather conditions, with very cold spring temperatures, followed by very hot conditions in July and August. Variety performance under these extremes offers an opportunity for review and comparison with regard to adaptability. Each of the companies offers a compliment of varieties that can serve to match various production strategies commonly employed in the state as well as showing a strong capacity to be regionally adaptive.
    • Assessing the Impact of Irrigation Management Strategies on Yield and Nitrate Leaching in Upland Cotton Production

      Martin, E. C.; Pegelow, E. J.; Watson, J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Although the cost for water is one of the largest expenditures in a grower's budget, many growers still over -irrigate their fields to assure that there will be no yield losses. Although these over -irrigations usually do not cause any negative effect to the crop, they can cause the loss of available nitrogen to the plant and the potential of nitrate contamination of groundwater resources. To assess what impact over-irrigation may have on yield and the potential for groundwater contamination, a drainage lysimeter study was initiated at the Maricopa Agricultural Center, Maricopa Arizona. Drainage lysimeters are large steel boxes with the tops open. In this study, three lysimeters were installed. The lysimeters were 80" wide (two row widths), five feet long, and six feet deep. They were placed 18 inches below the soil surface and filled with soil as to best represent the soil in its natural condition. On April 10, cotton was dry planted and watered up. Throughout the season, water samples were taken from the lysimeters and from suction lysimeters placed in the field. Nitrogen applications were made according to field conditions and weekly petiole sampling. Irrigations were made according to field conditions and using the AZSCHED irrigation scheduling program. Treatment one was irrigated according to the schedule and amount recommended by AZSCHED. In treatment two, the timing was the same as treatment one, but the amount applied was 0.25 times more. Treatment three was also irrigated at the same time but with 0.5 times more water. Yield samples were taken at the end of the season and showed no significant differences between treatments, with yields averaging about 1100 lbs /acre of lint. The drainage amounts ranged from 4" in treatment three to 1.5 inches in treatment one. The corresponding nitrate -N losses were 33 lbs/acre for treatment three and 20 lbs/acre for treatment one. Monitoring will continue over the winter to assess the impact of winter rainfall.
    • Chemical Control Studies of Silverleaf Whitefly Control

      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)
      Chemical control studies for silverleaf whitefly, Bemisia argentifolii Bellows and Perring, control on cotton showed that fenpropathrin-acephate, fenpropathrin-endosulfan, and endosulfan-bifenthrin mixtures gave adequate control and increased cotton yields were obtained as compared within untreated cottons. Pyriproxyfen, applied biweekly or alternated with fenpropathrin-acephate, Nicotiana, and a fenpropathrin-mycotrol mixture also gave effective control.
    • Comparison of Early Season and Mid-Season Applied Plant Growth Regulators on DPL 5415 Cotton

      Rethwisch, Michael D.; Rovey, Nathan; Heeringa, Nathan; Quist, Aron; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Several plant growth regulators were applied to DPL 5415 cotton to evaluate effectiveness on cotton lint yield. Growth regulators applied in small amounts over multiple applications early in the growing season reduced yields compared with the check while a single application applied at full-bloom slightly increased lint yields. High night time temperatures from late July into early September were detrimental for cotton production. Increased squaring of early season applications compared with the check may have resulted in reduced yields due to increased stress from temperatures and/or nutrient availability. Increased stress in the early treated (more fruit) plots may have had greater fruit abscission.
    • Comparison of Various Plant Growth Regulators on Pima S-7 Cotton Yields

      Rethwisch, Michael D.; Hurtado, Greg; Hurtado, Rosario; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      All plant growth regulators and nutritional products applied to Pima S-7 cotton during bloom economically increased lint yields, with increases ranging from 80 - 261 lbs. /acre. Greatest increase was noted with Boll-Set Plus, a product that contains raised levels of calcium and zinc. Cytokin and Boll -Set Plus significantly increased yields at one location. A lint yield increase of approximately 40 lbs/acre was noted when Tech-Flo Alpha was added to Cytokin. A single application of Foliar Triggrr resulted in equal yields as two applications of the Cytokin plus Tech-Flo Alpha.
    • 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.