• 1996 Low Desert Upland Cotton Advanced Strains Testing

      Husman, S. H.; Jech, L. E.; Metzler, F.; Wegener, R.; Johnson, K.; Silvertooth, Jeff; Maricopa County Cooperative Extension, University of Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Upland cotton advanced strains and commercial check comparison varieties were evaluated in replicated field studies in 1996 on Cooperator fields in Queen creek, Buckeye, and Gila Bend, AZ. Eight seed companies submitted advanced strains plus a commercially available check of their choice for each site. The highest lint yields for advanced strains entries by location were: J & S Research JSX 12 (1890 lb./acre), Delta Pine and Land Co. DPX 1075 (1420 lb/acre) and Delta Pine and Land Co. DPX 1075 (2510 lb/acre) at Queen Creek, Buckeye and Gila Bend, Arizona respectively.
    • 1996 Seed Treatment Evaluations

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      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 the first sample date at Marana with the treatment combination of NuFlow ND and Maxim having the highest percent emergence. Results from the second sample date at Marana were statistically significant but similar treatment ranking was observed. Results at Maricopa showed no statistically significant differences due to treatment for either sample date.
    • 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.
    • 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.
    • 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.
    • Arizona Upland Cotton Variety Testing Program, 1996

      Silvertooth, J.; Norton, R.; Clark, L.; Husman, S.; Knowles, T.; Howell, D.; Stedman, S.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Eleven field experiments were conducted in many of the cotton growing areas of Arizona in 1996 for the purpose of evaluating Upland cotton varieties in terms of adaptability and performance. Five commercial cottonseed companies participated in the program. Two varieties were submitted from each company at each location. Experiments were conducted on a commercial level on grower - cooperator fields in most cases. Locations used in the program spanned the range of conditions common to cotton producing areas of the state from about 100 ft. to 4,000 ft. elevation. Results indicated a broad range of adaptability and competitiveness. The 1996 season offered some extremes in terms of weather conditions, with very hot summer temperatures, particularly in July and August. The hot summer weather conditions were primarily difficult in relation to higher humidities (dewpoints) with high night and daytime temperatures. Variety performance under these extremes offers an opportunity for review and compare with regard to adaptability, or what is commonly referred to as "heat tolerance". The 1996 season was very similar in this respect. Each of the participating seed companies offer 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.
    • Commercial Field Performance of KNACK™ on Cotton in the Yuma Valley

      Palumbo, John C.; Hannan, Todd A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      The insect growth regulator, Knack was evaluated for efficacy against sweetpotato whitefly in paired plots within three commercial cotton fields near Somerton, Arizona. A single application of Knack and Danitol/Orthene was made in July and the impact on whitefly populations, natural enemies and secondary pests was measured for 40 d. Knack appeared to act slowly during the first 2 weeks, but after 21 days nymph populations were greatly reduced. Populations of nymphs and adults began to return to their pre-test levels after 40 d. The Danitol/Orthene application resulted in a significant decrease in adult numbers. Initially nymph densities declined, but after 14 d densities appeared to increase at a much greater rate than was observed in the Knack plots. Under the conditions experienced in this study, a single application of Knack in early July provided protection against sweetpotato whitefly as good, or better than experienced with Danitol/Orthene. Reductions in yields or lint quality attributable to whitefly were not observed in either treatment regime. Although beneficial predators were measured throughout the season, insecticide sprays for lygus control prevented significant buildup of populations. However, the numbers of Liriomyza leafminer adults captured on sticky traps were significantly lower in Knack-treated plots.
    • Conservation of Natural Enemies Relative to Use of Insect Growth Regulators for Control of Sweetpotato Whitefly

      Naranjo, Steven E.; Hagler, James R.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      As part of a large-scale, multi-institutional experiment in 1996 to examine and demonstrate strategies for management of Bemisia tabaci involving the use of two insect growth regulators (IGRs), we evaluated effects on the abundance and activity of native natural enemies. For parasitoids there were significant differences between insecticides regimes on 4 of 10 sampling dates. In general, parasitoid abundance and rates of parasitism were depressed in treatment plots receiving a rotation of conventional chemistry in comparison with those receiving IGRs. There was no apparent effect of any of the treatment variables on parasitoid emergence (immature survival). Results for arthropod predators are still preliminary, but densities were generally depressed in plots receiving a rotation of conventional insecticides in comparison with those receiving IGRs. These preliminary results suggest that use of IGRs for suppression of B. tabaci may help conserve populations of important natural enemies.
    • Control of Pink Bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) with Biocontrol and Biorational Agents

      Gouge, D. H.; Smith, K. A.; Payne, C.; Lee, L. L.; Van Berkum, J. R.; Ortega, D.; Henneberry, T. J.; Silvertooth, Jeff; Western Cotton Research Laboratory, Phoenix, AZ; biosys, Inc., Columbia, MD; Texas A & M University, Extension, El Paso, TX (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      At pre- sowing irrigation (mid-March), cotton fields were treated with two entomopathogenic nematode species; Steinernema riobravis and S. carpocapsae for control of diapausing Pectinophora gossypiella larvae. Pima S-6 cotton fields situated in Fort Hancock, Texas were treated at a rate of one billion nematodes per acre. Caged, diapausing larvae were buried in fields at a depth of one inch, in row tops and furrow bases. Nematodes were applied with a spray rig, fixed winged aircraft, or in furrow irrigation via a constant flow, battery box. Fields were irrigated after ground application, prior to aerial spraying and during furrow application. Caged larvae were recovered 48 hours after nematode application. All application methods resulted in uniform distribution of nematodes over the treated fields. No significant differences ir. larval mortality between nematode species or application method could be determined. However, aerial and furrow application methods gave consistently better parasitism of larvae compared to ground rig delivery. Larval mortality in cassettes buried in furrow bases was significantly higher than in row tops. Larval mortality ranged from 53.26-79.14 %. Both nematode species could be recovered 50 days post application. At pin-head square Frustrate® PBW pheromone bands (biosys, Inc.) were applied at 100 bands per acre placement rate (16 g a. i./acre), giving a target release of 115 mg gossyplure/acre/day. Capillary gas chromatography was used to analyze bands throughout the growing season. A uniform release profile indicated sufficient release of pheromone for 144 days after placement. Pink bollworm mating disruption was monitored in three ways: 1. Delta 2 traps were positioned throughout the farm, forming a continuous trap line. Significantly larger numbers of moths were recovered form untreated zones. 2. Virgin female moths were placed in mating stations at dusk. At sun rise moths were collected and later dissected for spermatophores. Significantly higher mating activity occurred in untreated fields (p= 0.000). 3. Green bolls were collected at random and examined for larvae. Significantly higher infestation levels existed in untreated zones. At harvest (November), seed cotton yields were weighed using trailer scales. Higher yields were recovered from pheromone (1,864 lb/acre), and pheromone + nematode fields (1,712 lb/acre), than control fields (1,450 lb/acre). However, due to large variations between fields, the differences were not statistically significant (p = 0.436).
    • 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.
    • 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.
    • Defoliation of Pima and Upland Cotton at the Safford Agricultural Center, 1996

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Nine 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 1996

      Nelson, J. M.; Hart, G. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      Defoliation tests were conducted on Upland and Pima cotton at the Maricopa Agricultural Center to evaluate rates of Ginstar, tank mixes of Ginstar with other defoliants and spray adjvants, and Ginstar used as a preconditioner. The cotton used in these tests was generally difficult to defoliate, probably because of an excessive supply of nitrogen and cool temperatures in October and November. In September tests, no treatment gave acceptable defoliation of Upland cotton and only the highest rate of Ginstar and the Ginstar + Def treatment were effective on Pima cotton. In October and November tests, temperatures were cool and Upland cotton was not consistently defoliated by a single application of defoliant. Pima cotton was effectively defoliated by Ginstar treatments in early October and November tests. Under cool weather conditions when defoliation was very difficult, Ginstar used as a preconditioner at .047 lb. a. i./acre followed by Ginstar at .094 lb. a. i./acre generally gave acceptable defoliation.
    • 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.
    • 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), 1997-03)
      A series of boll measurements were taken at numerous locations across the state in 1995 in an attempt to continue to develop a yield prediction model that began in 1993. Results from 1995 showed the strongest relationship between final open boll counts and yield. Based on these results, data was collected in 1996 from several locations around the state. Boll counts were made just prior to harvest and then correlated to yield. Results showed that a good estimate for lint yield could be obtained using the factor of approximately 13 bolls/row-ft./bale of lint for Upland cotton on a 38 to 40 inch row spacing.
    • 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), 1997-03)
      A single field experiment was conducted in 1996 at Maricopa, AZ to compare a scheduled approach (based on stage of growth) versus a feedback approach (based on vegetative status) to both nitrogen (1V) 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) with respect to established baselines. Scheduled and feedback PIX applications were made for a total of 0.75 and 1.25 pt./acre, respectively, with the scheduled treatments being initiated earlier in the fruiting cycle (early and peak bloom). Feedback PIK treatments consisted of a single 0.75 pt./acre application near peak bloom (approx. 2200 heat units after planting (HUAP), 86/55°F threshold). Scheduled applications of fertilizer N totaled 225 lbs. N/acre from three applications and feedback N treatments received a total of 135 lbs. N/acre from three applications. Treatments consisted of all combinations of scheduled or feedback applications of both N and PIX The highest lint yields were from a treatment receiving feedback N and PIX, 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 1996 are consistent with 1993, 1994, and 1995 results from the same study.
    • Evaluation of Calcium Soil Conditioners in an Irrigated Cotton Production System

      Griffin, J. R.; Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      In 1996 a single field experiment was conducted at Paloma Ranch, west of Gila Bend in Maricopa County Arizona. Nucoton 33B was dry planted and watered -up on 15 April. Treatments consisted of various rates and times of application of nitrogen (N) and calcium (Ca) from two sources (N-Carm and CAN-17), as well as a standard N source, UAN-32, along with a Calcium (Ca) check which received no Ca. Treatments], 2, and 3 each received a total of 280 lbs. N/acre. Treatment 4 received a total of 210 lbs. N/acre while treatment 5 received a total of 301 lbs. N/acre. Treatment 1 was a check plot and received only standard applications of UAN-32. Treatments 2 and 4 each received a total of 72 lbs. of Ca/acre. Treatment 5 received a total of 79 lbs. Ca/acre while treatment 4 received a total of 300 lbs. Ca/acre. No significant differences were found among the various treatments in terms of plant growth, soil water content, ECₑ values, and sodium absorption ratios. Lint yields were significantly different (P < 0.07).
    • 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.
    • Evaluation of Late Season Pix™ Applications

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1997-03)
      The effects of late-season Pix™ on the growth characteristics and yield of Upland cotton was examined in this study. Three treatments were imposed late season (3447 HUAP), 1, a check plot, receiving no Pix™; 2 receiving 0.75 pt/acre, and 3; receiving 1 pt/acre. The imposed treatments did not have a statistically significant effect on plant growth characteristics or earliness, nor were there any significant overall yield differences detected among treatments.