• Demonstration to Manage Pink Bollworm with BT Cottons, Yuma Valley Ag Center, 1996

      Howell, Don R.; Palumbo, John; Tellez, Alfonso; Hernandez, Humberto; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Transgenic cotton with the Bollgard™ gene inserted has shown great promise in controlling pink bollworm infestations in cotton. This trial was superimposed over a variety trial. Evaluations of pbw infestation indicated remarkable control even though the bolls became infested. Yields were increased in this trial when almost 100% infestation of pbw was allowed to occur. It appears that the trangenic cottons containing Bollgard™ may be an effective method of pbw control.
    • Evaluation of Irrigation Termination Management on Yield of Upland Cotton

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      A single field study was conducted in 1996 at the Maricopa Agricultural Center (1,175ft. elevation) to evaluate the effects of two dates of irrigation termination on the yield of a common Upland cotton variety (DPL 5415). Planting date was 11 April (667 HU/Jan 1 86/55° F thresholds. Two dates of irrigation termination (IT1 - IT2) were imposed based upon crop development into cut-out, with IT1 (14 August) being provided such that bolls set at the end of the first fruiting cycle would not be water stressed and could be fully matured The second termination (IT2) date was 10 September, which was staged so that soil moisture would be sufficient for development of bolls set up through the first week of September. Lint yield results revealed no differences between IT1 and IT2.
    • Irrigation Efficiencies and Lint Yields of Two Upland Cotton Varieties Grown at the Maricopa Agricultural Center, 1996

      Sheedy, Mike; Watson, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      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 conjunction 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 60, 66, 72, and 74 %, respectively. The low efficiencies are due in part to the inherent inefficiency of irrigations in the early season. There was no lint yield response to the different irrigation efficiencies, and no difference in yield between the two varieties. Lint Yields ranged from 1146 # lint/acre (SG125 at 75 %) to 925 # lint /acre (SG 125 at the 95 % irrigation efficiency).
    • Upland and Pima Cotton Demonstration Using IGR's Knack and Applaud to Control Silverleaf Whitefly at the Yuma Valley Ag Center in 1996

      Howell, D. R.; Palumbo, J.; Nelson, J.; Hernandez, H.; Gayler, R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      The section 18 granted for the use of insect growth regulators in 1996 in Arizona provided an excellent opportunity to demonstrate the efficacy of the materials. Knack® (Pyriproxyfen) and Applaud® (Buprofezin) both demonstrated excellent control of whitefly in this demonstration. Efficacy of the insect growth regulators was monitored by using the "Ellsworth-Naranjo" methods of measuring adult and nymph whitefly numbers. This method provided good tracking of the populations throughout the period monitored. The areas treated were cotton variety trials both pima and upland. On the upland trial whitefly infestation data was collected on each variety. Hairy leaf varieties tended to have higher whitefly numbers of both adults and nymphs.
    • Suppression of Plant Parasitic Nematodes in Cotton Using the Antomopathogenic Nematode Steinernema Riobravis (Cabanillas, Poinar, and Raulston) (Rhabditida: Steinernematidae)

      Gouge, D. H.; Smith, K. A.; Payne, C.; Lee, L. L.; Van Berkum, J. R.; Henneberry, T. J.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory, Columbia, MD; biosys Inc. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Cotton fields were treated with the entomopathogenic nematode, Steinernema riobravis, and Vydate® L for the control of plant parasitic nematodes. Short staple cotton grown near Coolidge, Arizona, was treated at a rate of 1 billion and 2 billion S. riobravis nematodes per acre, and 0.5 lb a.i. Vydate® L per acre. Untreated cotton received an application of water only. Treatments were applied through a subterranean drip system with 12 inch spaced outlets. Applications were made in the daily irrigation cycle of 0.33 inches of water, normal irrigation cycles followed Products were uniformly distributed over the treated fields. Entomopathogenic nematodes persisted throughout the 6 week experimental period at the 1 billion per acre rate. However, nematodes applied at 2 billion per acre rate disappeared rapidly. Populations of various plant parasitic nematode species were monitored subsequent to treatment application. Nematodes were extracted using a standard sugar flotation technique and counted in I ml slide samples. Both Meloidogyne incognita and Tylenchorhynchus spp. populations were reduced by S. riobravis applied at 1 billion per acre rate. Phytoparasitic nematodes were reduced following application of Vydate® L, but control was not sustained beyond one week.
    • The 1997 Arizona Cotton Advisory Program

      Brown, P.; Russell, B.; Silvertooth, J.; Ellsworth, P.; Stedman, S.; Husman, S.; Howell, D.; Knowles, T.; Clark, L.; Dunn, D.; et al. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Arizona Cooperative Extension generates and distributes weather-based Planting Date and Cotton Development Advisories for 15 cotton production areas (Marana, Laveen, Paloma, Litchfield Pk., Pinal Co., Parker, Mohave Valley, Queen Creek, Safford, Yuma Valley, Aguila, Cochise Co., Greenlee Co., Harquahala and Wellton-Mohawk). Planting Date Advisories are distributed from shortly after legal first planting date until the end of April and stress 1) planting cotton varieties according to heat unit accumulations rather than calendar date and 2) the importance of weather conditions and 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 1997, and growers may obtain advisories by mail /fax from local extension offices or by computer from the AZMET computer bulletin board system or AZMET Internet Web Page (http://ag.arizona.edu/azmet). Major program changes planned for 1997 include 1) providing heat stress information on Crop Development Advisories and 2) the addition of an advisory for the Wellton-Mohawk area.
    • Aflatoxin Contamination of Bt Cottonseed

      Cotty, P. J.; Howell, D. R.; Bock, C.; Tellez, A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Transgenic Bt cotton may have reduced susceptibility to aflatoxin contamination as a result of pink bollworm resistance. During 1995 and 1996, Bt cottonseed from several commercial fields in Arizona contained aflatoxin levels unacceptable for dairy use. Comparison of cottonseed with and without BGYF (bright-green-yellow fluorescence) from one highly contaminated (> 6,000 ppb aflatoxin Bj) Bt seed lot indicated that most contamination probably resulted from exposure of mature cotton to high humidity. Seed exhibiting BGYF was repeatedly detected in Bt cottonseed lots but, pink bollworm exit holes were not observed in the field. A field plot test in 1996 demonstrated high resistance among Bt cultivars to both pink bollworm damage and formation of BGYF seed cotton. These observations suggest that resistance to pink bollworm will result in reduced aflaaoxin contamination when pink bollworm pressure coincides with conditions conducive to Aspergillus flavus infection. However, Bt cultivars are not resistant to aflatoxin increases occurring after boll opening and large quantities aflatoxin can form during this period. If insect control provided by Bt cultivars leads growers to hold crops in the field longer, most advantages of Bt cotton in aflatoxin management may be lost. Combined use of Bt cultivars and atoxigenic strains of A. flavus may result in the most reliable control of aflatoxin contamination.
    • Short Staple Variety Demonstrations, Graham County, 1996

      Clark, Lee J.; Cluff, Ronald E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      TWO on farm, replicated short staple variety demonstrations were established in 1996. Twelve varieties were evaluated on the Carpenter farm in Solomon and on the Colvin farm in Eden. Several new varieties were planted in both studies, including 2 varieties from Stoneville, 2 varieties from Australia and DP 35B, the Bt version of DP 5690. Delta Pine 5690 and DP 35B were the highest yielding varieties with yields of 1697 and 1220 pounds of lint per acre at the Solomon and Eden locations, respectively.
    • Seasonal Infestation by Pink Bollworm of Transgenic Cotton, NuCOTN 33, and Parental Cultivar DPL-5415 in Commercial Fields: the Second Season

      Flint, H. M.; Parks, N. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Bolls from transgenic cotton, NuCOTN 33 (Delta and Pine Land Co.) containing the Bollgard™ gene (Monsanto Co.) and from the parental cultivar DPL-5415 were examined for mature larvae of the pink bollworm (78,240 total bolls). Bolls from paired fields were collected in the Queen Creek, Buckeye, Maricopa, and Marana, AZ, areas. Equal numbers of bolls were collected from the edges of each field each week July - October except for Marana where a single collection was made 30 October. Bolls were incubated for 2 weeks and/or dissected from 1 September onward. Numbers of pink bollworm larvae were very low in all fields through August and increased to extremely high levels (up to 3.4 larvae/boll at Marana) in some control fields in October. Numbers of pink bollworm found in NuCOTN 33 were extremely low or nonexistent, even in fields immediately adjacent to heavily infested control fields. The overall numbers of larvae found in NuCOTN 33 were comparable to those found in 1995. In 1995, the percent worms of bolls were: NuCOTN 33 = 0.0003 (13 larvae /38320 bolls) compared to 11.80% for DPL -5415 (4711 larvae /39920 bolls). Overall percent worms of bolls for 1996 were: NuCOTN 33 = 0.0004% (14 larvae/33350 bolls) compared to 34.19% (11572 larvae/33850 bolls) in DPL-5415.
    • Silverleaf Whitefly on Cotton

      Chu, C. C.; Henneberry, T. J.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory, Brawley, CA and Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Silverleaf whiteflies (SLW), Bemisia argentifolii Bellows and Perring, have been devastating pests of cotton and other crops in Arizona and California in recent years. Studies with cotton insecticide treatments initiated each week from shortly after cotton seedling emergence to late in the cotton season were conducted at the Irrigated Desert Research Station, Brawley, CA. The results suggest action thresholds in relation to cotton yield of 0.22 SLW nymphs/cm² of leaf disc, 0.64 eggs/cm² of leaf disc or 2.22 adults/cm² of yellow sticky card surface.
    • Monitoring Whitefly Susceptibility to Applaud

      Yasui, M.; Ellsworth, P. C.; Lublinkhof, J.; Comer, D.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      A bioassay developed by one of the authors (MY) in 1993 was used to monitor susceptibility of sweetpotato whitefly to Applaud in five different field locations. Whitefly populations were exposed to from 0 (untreated fields) to 4 (small plot trial) applications of Applaud. Susceptibilities of whiteflies, as measured by LC₅₀s and LC₉₅s, did not increase with exposure to Applaud (0 to 4 applications) nor since baseline measurements of susceptibility were made in 1993. Under current patterns of use (single use), risk of resistance to Applaud appears to be minimal.
    • Date of Planting by Long Staple Variety Trial, Safford Agricultural Center, 1996

      Clark, L. J.; Carpenter, E. W.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Four varieties of Long Staple cotton were tested over three dates of planting in this study. Two later maturing varieties, Pima S-6 and Oro Blanco, and two earlier maturing varieties, Pima S-7 and Conquistador (OA 312), were planted at three dates ranging from early April to mid May to find the optimal planting times as well as the yield reduction effects of planting too late for a particular variety.
    • Upland Advanced Strains Cotton Variety Test at the Maricopa Agricultural Center, 1996

      Hart, G. L.; Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Twenty five upland advanced strains were grown in a replicated trial at the Maricopa Agricultural Center. Lint yield, boll size, plant population, plant height and fiber property are presented in this report.
    • Using Drainage Lysimeters to Evaluate Irrigation and Nitrogen Interactions in Cotton Production

      Martin, E. C.; Pegelow, E. J.; Watson, J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Although the cost for water is one of the largest expenditures in a grower's budget in Arizona, many growers in the state still over- irrigate their fields to assure that there will be no yield losses. These excess irrigations usually do not cause any negative effects to the crop, they can cause the loss of available nitrogen to the plant and the potential for nitrate contamination of groundwater resources. To assess the impact that excess irrigation may have on cotton yields and the potential for groundwater contamination, a drainage lysimeter study was initiated at the Maricopa Agricultural Center, Maricopa, Arizona. Drainage lysimeters are large, open- topped steel boxes filled with soil and placed underground in the experimental field. Crops are grown directly above the lysimeters and the water that moves through the soil profile is collected at the bottom of the lysimeter and analyzed. 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. The data presented in this paper are from two years of an ongoing experiment. Throughout the growing season, water samples were taken from the lysimeters 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 recommended by AZSCHED. The amount applied was equal to the total crop water use since the last irrigation. In treatment two, the timing was the same as treatment one, but the amount of irrigation water applied was 1.25 times more. Treatment three was also irrigated at the same time but with 1.5 times more water. Yield samples were taken at the end of each season and showed no significant differences between treatments, with yields averaging about 1100 lb./acre of lint in 1995 and 940 lb./acre of lint in 1996. The drainage amounts ranged from 9.5" in treatment three to 2.5 inches in treatment one. The corresponding nitrate-N losses were 56.9 lb. N/acre for treatment three and 33.4 lb. N/acre for treatment one. Monitoring continued during the winter to assess the impact of winter rainfall. In the last two years, there has been no significant winter rainfall.
    • Cotton Defoliation Evaluations, 1996

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Two field experiments were conducted near Coolidge and Marana, AZ in 1996 to evaluate the effectiveness of a number of defoliation treatments on Upland (var. DPL 5415) and Pima (var. S-7) cotton.. All treatments consisted of materials commercially available in Arizona, and each showed promise in terms of overall effectiveness. Results do reinforce recommendations regarding the use of low rates (relative to the label ranges) under warm weather conditions and increasing rates as temperatures cool.
    • Cotton Heat Stress

      Brown, Paul B.; Zeiher, Carolyn A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Heat stress has been a subject of considerable concern among Arizona cotton growers due to a recent string of hot, humid summers. Research studies indicate heat stress develops when mean crop temperature exceeds 82.4F (28C). Serious heat stress develops when mean crop temperatures exceed 86E Several meteorological factors impact crop temperatures in Arizona; however, accurate estimates of crop temperature can be made using a model requiring air and dew point temperature. This model was used to evaluate heat stress conditions in Arizona over the past 10 years. Results from this evaluation show the past three years were difficult years for heat stress. Elevation and humidity levels are major factors impacting heat stress in any given year. Lower elevation areas are more prone to heat stress than high elevation areas such as Safford. Possible management options to minimize the impact of heat stress include early optimal planting dates, variety selection, field location and good water management.
    • Field Determination of Permanent Wilting Point

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Water is a vital resource for cotton production in the desert Southwest. One method of managing irrigation water is through the use of a "checkbook" approach to irrigation scheduling. This involves irrigating based upon the percent depletion of plant available water (PAK9 from the soil profile. In order to effectively utilize this method of irrigation scheduling soil water content values at field capacity (FC) and permanent wilting point (PWP) must be defined. In this study the PWP values were characterized for Iwo different soil types, one at Maricopa, AZ and another at Marana, AZ. The possibility of having different values for PWP as a function of crop stage of growth was also investigated in this study. Results demonstrated differences in both FC and PWP values between the two locations. Differences were also observed as a function of crop growth stage in the pattern of soil water extraction.
    • 1996 Weather Conditions

      Brown, P.; Russell, B.; Machibya, T.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Weather again presented significant challenges to Arizona cotton producers in 1996. Warm early season weather allowed most growers to plant earlier than normal and the 1996 crop moved through the first half of the season in excellent shape. The arrival of high monsoon humidity in early July combined with high July temperatures to create heat stress conditions which led to fruit shed at most central and western production areas. The stressful combination of humidity and temperature remained entrenched through much of July and August, creating generally poor fruiting conditions in both months. Monsoon activity continued through mid-September in many areas, then was followed by a month of generally good weather conditions for finishing the crop. Cool weather effectively ended the growing season after mid-October. The overall warm year produced seasonal heat unit accumulation well in excess of normal. Precipitation was generally well below normal, especially along the Colorado River.
    • Short Staple Variety Trials in Cochise County, 1996

      Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Variety trials were grown at two locations and with two different sets of short staple varieties. One trial on the Robbs farm, north of Kansas Settlement, tested seven acalas varieties from New Mexico and California and one variety from Australia. The other trial on the Noel Curry farm, near the town of Cochise, tested nine upland varieties as part of the statewide testing program and three acalas from NM and CA. The highest yielding variety in our tests was SG 125 with a yield over 3 bales per acre. In the acala study, the Australian variety and an experimental from NM were the highest yielding varieties with yields just over 2 bales per acre. Lint quality of each variety and an estimated crop value are also given in this paper.
    • Agronomic Evaluations of Bt Cotton

      Silvertooth, J. C.; Norton, E. R.; Husman, S. H.; Knowles, T.; Howell, D.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      In 1996 transgenic Bt cotton was first grown on a commercial level in Arizona and the U.S. cottonbelt. Insecticidal properties of Bt varieties had been evaluated rather thoroughly in both the private and public sectors prior to commercial release. However, the agronomic characteristics had not been evaluated to any sufficient extent beyond the level of the developing companies. Lab and field tests were conducted in Arizona in 1996 dealing with the Delta and Pine Land Co. (DPL) companion varieties 5415/NuCOTN 33b (similar to 5415 but with the Bt gene) and 5690/NuCOTN 35b (with Bt gene). Most field comparisons were between 5415 and 33b. Lab and field studies revealed very similar agronomic characteristics between the companion varieties. No differences were detected with respect to heat tolerance, as determined by comparative fruit loss and abortion rates at the onset of the monsoon season. Only slightly higher vigor or growth rates were noted for 33b over 5415, which was considered to be negligible. Yield results revealed higher lint yields for 33b over 5415 in most cases. The difference in yields were attributed to pink bollworm infestations and damage, even when chemical control measures were being taken. It was concluded that 33b, as a transgenic version of 5415, is indeed very close to it's non-Bt counterpart.