• Preliminary Evaluation of the "Next Generation" of Bt Cotton

      Sieglaff, D. H.; Ellsworth, Peter C.; Silvertooth, Jeffrey C.; Hamilton, E.; Silvertooth, Jeff; The University of Arizona, Department of Entomology & Maricopa Agricultural Center; Department of Plant Sciences; Monsanto Company, Chesterfield, MO (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      The next generation of Bollgard® cotton was evaluated for agronomic and insecticidal efficacy under central Arizona growing conditions. Two novel lines were compared with their recurrent parents, DP50 and DP50B. There were no seasonlong differences observed among the varieties in most plant development and insect parameters. However, DP50 had significantly lower emergence than the other lines tested (possibly related to seed quality). The lower plant population may have been responsible for greater whitefly abundance observed on two dates mid-season. During early-season ratings of secondary “pests” (15 DAP) (scaled on damage and/or presence), the two test lines received lower ratings for thrips and flea beetle when compared with DP50, DP50B and DP50Bu (untreated for Lepidoptera). However, these difference are likely as a result of the difference in seed treatments that the two test lines received (Gaucho®) and the others did not. This seed treatment does have known activity against thrips and beetle pests. In mid-season, the two test lines received lower ratings for beet armyworm when compared to DP50, DP50B and DP50Bu (although, not significantly different from DP50B or DP50Bu). Efficacy against pink bollworm (PBW) was assessed one time at the end of the season (we were limited to this time, so as to not affect yield), and DP50 was the only variety in which PBW exit holes were observed and PBW larvae collected. However, the low Lepidoptera pressure experienced during the season limited assessments of the two novel lines’ efficacy toward PBW. There was no significant difference in yield (bale/A) among the varieties. Although, one of the test lines had a lower lint turnout than each other variety. The two novel Bollgard lines performed well under our growing conditions, but continued evaluations will be necessary under more conditions and more insect pressures before “varietal” performance and gene efficacy can be assessed adequately.
    • 1998 Low Desert Upland Cotton Advanced Strains Testing Program

      Husman, Stephen J.; Wegener, R.; Johnson, K.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Upland cotton advanced strains and commercial check comparison varieties were evaluated in replicated field studies at three locations in 1998. The test sites include Buckeye, Az., Maricopa, Az., and Safford, AZ. Twelve seed companies submitted a maximum of five advanced strains entries per location. Three commercial check varieties were used at each site for comparison purposes and included DPL 5415, SG 125, and STV 474.
    • The 1999 Arizona Cotton Advisory Program

      Brown, P.; Russell, B.; Silvertooth, Jeffrey C.; Ellsworth, Peter C.; Olsen, Mary W.; Husman, Stephen H.; Walser, R.; Clark, L.; Dunn, D.; Schneider, M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Arizona Cooperative Extension generates and distributes weather-based Planting Date and Cotton Development Advisories for 19 cotton production areas (Aguila, Buckeye, Cochise Co., Coolidge, Eloy, , Laveen, Litchfield Pk., Marana, Maricopa, Mohave Valley, Paloma, Parker, Pinal Co., Queen Creek, Roll, Safford and Yuma Valley). Planting Date Advisories are distributed from legal first planting date until the end of April and provide updates on heat-unit-based planting windows, recent and forecasted weather conditions, heat unit accumulations, variety selection, soil temperatures, recommended plant population, and early insect management and control. Cotton Development Advisories are distributed from early May through early September and provide updates on crop development, insects, weather and agronomy. The Cotton Advisory Program will continue in 1999, and growers may obtain advisories by mail/fax from local extension offices or by computer from the AZMET Internet Web Page (http://ag.arizona.edu/azmet). Major program changes planned for 1999 include 1) use of historical AZMET weather data for local normals and 2) elimination of the computer bulletin board as a computer-based means of retrieving the advisories.
    • Monitoring Bemisia Susceptibility to Applaud (buprofezin) during the 1998 Cotton Season

      Ellsworth, Peter C.; Sieglaff, D. H.; Yazui, M.; Lublinkhof, J.; Silvertooth, Jeff; The University of Arizona, Department of Entomology & Maricopa Agricultural Center; Nihon Nohyaku, Ltd., Osaka, Japan; AgrEvo USA Co., Wilmington, DE (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Starting in 1993, we developed a field-based protocol for bioassaying sweetpotato whiteflies (SWF) for susceptibility to buprofezin (Applaud®). Since then, we have monitored Arizona SWF populations (up to 5 regions) for susceptibility to Applaud in four out of the last six seasons. We observed no appreciable decrease in susceptibility. Instead, we have observed an increase in susceptibility of present day whiteflies when compared to populations bioassayed in 1993 and 1996, before any Applaud use in the U.S.. This result, however, is likely related to various procedural changes in the bioassay methodology. Nevertheless, our current estimates of whitefly susceptibility are similar to those obtained from various unexposed populations from around the world and to populations we bioassayed in 1997. Differences between our LC50 estimates and those of some other researchers can probably be explained by various procedural differences: 1) method of Applaud application, 2) whitefly stage collected and sources of leaf foliage, and 3) bioassay environmental conditions. Our results also showed each year that Applaud susceptibility does not decline after Applaud application(s) based on commercial paired field comparisons and replicated small and large plot evaluations. In fact, susceptibilities actually marginally increased after an Applaud application. This fact does not alter the recommendation for Arizona to limit Applaud use to one time per crop season, but does provide hope for the development of a sustainable use pattern even if usage continues on non-cotton hosts (i.e., on melons and vegetables under Section 18). Given the tremendous value of this mode of action, however, commodity groups should work together wherever possible to coordinate the usage of this and other valuable compounds so that whitefly generations are not successively exposed to this product.
    • Evaluation of Planting Date Effects on Crop Growth and Yield for Upland Cotton, 1998

      Norton, Eric R.; Silvertooth, Jeffrey C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      A field study was conducted in 1998 at the University of Arizona Marana Agricultural Center (1,974 ft. elevation) to evaluate the effects of three planting dates on yield and crop development for three Upland varieties. Planting dates ranged from 9 April to 28 May and 342-885 heat units accumulated since Jan 1 (HU/Jan 1, 86/55o F thresholds). Crop monitoring revealed early season fruit loss leading to increased vegetative growth tendencies with all three planting dates. General trends also showed decreasing lint yield with the later dates of planting for all varieties. The more determinate variety (STV 474) was able to set and a fruit load more rapidly than the other varieties in this study at several dates of planting, which resulted in higher yields.
    • Short Staple Variety Trials in Cochise County, 1998

      Clark, Lee J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      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 two acala varieties and the most promising advanced strain from New Mexico, two short seasoned varieties from SureGrow and one Australia variety. The other trial on the Glenn Schmidt farm, in Kansas Settlement, tested seventeen upland varieties as part of the statewide testing program. The highest yielding variety in the Robbs trial was SG 404 with SG 125 coming in second. In the Schmidt trial, FM 989, an Australian variety that has performed well in Safford, had the highest yield, just over 2 bales per acre.
    • Marana Pima Test

      Hart, G. L.; Nelson, J. M.; Barney, Glen; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Seventeen pima cotton varieties were grown at the Marana Agricultural Center as part of the national cotton variety testing program. Lint yield, boll size, lint percent and fiber properites are presented in this report.
    • Mortality Factors Affecting Whitefly Populations in Arizona Cotton Management Systems: Life Table Analysis

      Naranjo, Steven E.; Ellsworth, Peter C.; Silvertooth, Jeff; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ and 2University of Arizona, Maricopa, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Direct-observation studies were conducted in replicated experimental plots to identify causes and estimate rates of mortality of whiteflies in cotton over the course of six generations from late June through late October. In plots receiving no whitefly or Lygus insecticides, predation and dislodgment were major sources of egg and nymphal mortality, and overall survival from egg to adult ranged from 0-18.2%. Similar patterns were observed in plots treated with the insect growth regulator (IGR) Knack. Applications of the IGR Applaud or a mixture of endosulfan and Ovasyn caused high levels of small nymph mortality and reduced rates of predation on nymphs during the generation immediately following single applications of these materials in early August. Whitefly populations declined to very low levels by mid-August in all plots, and few differences were observed in patterns of whitefly mortality among treated and control plots 4-6 weeks after application. The population crash was associated with an unknown nymphal mortality factor which reduced immature survivorship during this first posttreatment generation to zero. The application of insecticides for control of Lygus in subplots modified patterns of mortality in all whitefly treatments by generally reducing mortality from predation during generations observed from mid-July through August. Parasitism was a very minor source of mortality throughout and was unaffected by whitefly or Lygus insecticides.
    • How to Obtain Cotton Advisories from the Internet

      Brown, P.; Russell, B.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Weekly advisories developed by the Arizona Cotton Advisory Program are now available from the Internet. Nineteen location-specific advisories are developed each Monday morning and then transferred to the Main AZMET Internet Web Page located at URL address http://ag.arizona.edu/azmet. To retrieve advisories from the Internet users must 1) log on to the Internet using the procedures required by your Internet service provider; 2) enter the URL for the Main AZMET Web Page; 3) move to the Cotton Advisory sub-page; and 4) select the advisory of interest. Advisories for the most recent week, this year to date, and all of 1998 are available at this Internet address.
    • Late Season Pink Bollworm Pressure in the Top Crop of Bt and Non-Bt Cotton

      Knowles, Tim C.; Dennehy, Tim J.; Rovey, Albert; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Green bolls (100/field) were sampled from the uppermost internodes within adjacent fields of Bt (Deltapine 33B) and non-Bt refuge (Hyperformer HS 44 or Deltapine 20) experiencing severe pink bollworm pressure late in the growing season. Evidence of 3rd instar or larger pink bollworm larvae survival was higher in susceptible bolls sampled from transgenic Bt cotton late in the 1998 growing season, compared to that observed late in the 1997 growing season.
    • Evaluation of the Effects Added Nitrogen Interaction on Nitrogen Recovery Efficiency Calculations

      Norton, Eric R.; Silvertooth, Jeffrey C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Two studies were conducted in 1996 and 1997 at the University of Arizona Maricopa Agricultural Center (MAC) to evaluate the added nitrogen interaction (ANI) or ‘priming effect’ on the determination of nitrogen recovery efficiencies (NRE). The method employed was to compare NRE’s as calculated by two different methods; the difference technique and the isotopic technique. The difference in NREs observed between the two methods indicates the extent of an ANI. Results demonstrated no statistical differences between NRE’s calculated by the two methods. Therefore, no ANI was observed in the field. These results indicate that the less expensive method of calculating NREs (difference technique) is sufficient under irrigated cotton production systems in the desert Southwest.
    • Pima Regional Variety Test at the Maricopa Agricultural Center, 1998

      Hart, G. L.; Nelson, J. M.; Clark, Lee J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Seventeen Pima varieties were grown in a replicated trial at the Maricopa Agricultural Center as part of the national cotton variety testing program. Lint yield, boll size, lint percent, plant populations, plant heights and fiber properties are presented in this report.
    • Evaluation of a Feedback Approach to Nitrogen and Pix Applications, 1998

      Norton, E. J.; Silvertooth, Jeffrey C.; Norton, Eric R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      A single field experiment was conducted in 1998 at Marana, AZ to evaluate a scheduled (based upon stage of growth) versus a feedback approach (based upon growth parameters and crop conditions) to nitrogen (N) and mepiquat chloride (PixTM) applications on upland cotton (Gossypium hirsutum L.). The parameters used in evaluating feedback applications for both N and Pix included fruit retention (FR) levels and height to node ratios (HNRs) with respect to established baselines for cotton grown in the desert Southwest. Scheduled and feedback Pix applications were made for a total of 1.5 and 2.5 pint Pix/acre, respectively, with the feedback treatments receiving a late season application at approximately 3100 heat units after planting (HUAP 86/550 F threshold). Scheduled Pix treatments received a single 1.5 pint Pix/acre application prior to peak bloom (approximately 2000 HUAP). Scheduled applications of fertilizer N totaled 205 lbs. N/acre from three applications. Feedback applications of N received a total of 100 lbs. N/acre from two applications. Treatments consisted of all combinations of feedback and scheduled applications of both N and Pix. The highest lint yields occurred in the treatment consisting of Pix feedback and N feedback (treatment two), however, there were no significant differences (P≥0.05) among any of the treatments with respect to yield.
    • Development of a Yield Projection Technique for Arizona Cotton

      Norton, Eric R.; Silvertooth, Jeffrey C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      A series of boll measurements were taken at numerous locations in cotton producing areas across Arizona in 1998 in an attempt to continue to develop a yield prediction model with a project that began in 1993. Results from 1995 showed the strongest relationship between final open boll counts and yield compared to a number of other measurements. Based on these results, data collection on boll counts began in 1996 and has continued in 1997 and 1998. Boll counts were taken as the number of harvestable bolls meter-1. All boll count measurements were made within one week of harvest. Number of bolls per unit area were then correlated to lint yield and an estimate for the number of bolls per area needed to produce a bale of lint was calculated. Estimates using all three years data combined indicate that approximately 38 bolls meter-1 are needed to produce one bale of lint per acre.
    • Evaluation of Chemical Controls of Lygus hesperus in Arizona

      Ellsworth, Peter C.; Silvertooth, Jeff; The University of Arizona, Department of Entomology & Maricopa Agricultural Center (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      When other means fail to avoid damaging levels of an insect pest population, chemical control becomes necessary. Chemical control is a variable farm input which should be optimized to reduce economic damage by the pest while maximizing profit and minimizing exposure to secondary pest outbreaks, pest resurgence, and risks of insecticide resistance. To best balance these needs, a grower or PCA needs the best information possible for selecting and timing chemical controls. This study examines the array of Lygus chemical control options currently available as well as experimental compounds that may or may not be available in the future. While identifying the best chemical controls is the major objective of this study, insights into proper timing and duration of control are also discussed. In short, there are few, yet effective, Lygus insecticides available to growers currently. However, with proper rates and timing, significant yield protection can be achieved with Orthene® or Vydate®. To a lesser extent, Thiodan® (endosulfan) was also effective against Lygus, though higher rates than used in this study may be necessary to achieve acceptable control. The use of mixtures did not enhance control of Lygus over our two standards (Orthene or Vydate). Newer compounds were also studied; however, Mirids (plant bugs) are not worldwide targets for development by the agrochemical industry. Thus, most new compounds are effective on some other primary pest (e.g., whiteflies, boll weevil, thrips, aphids), and control of Lygus is merely a potential collateral benefit. Of these, the chloronicotinyls (e.g., Provado®, Actara®) were not practically effective against Lygus hesperus, in spite of their existing or pending labelling. Their labels are based on demonstrated efficacy against a related species present in cotton outside of the West (Lygus lineolaris). One compound shows excellent promise as a Lygus control agent, Regent® (fipronil). Under development by Rhône- Poulenc, this insecticide provides as good or better protection against Lygus than our best materials. In a system demanding multiple applications to control chronic Lygus populations, Regent could be key to the development of a sustainable use strategy that does not over rely on any single chemical class. None of the insecticides tested significantly controlled adult Lygus, except after repeated use and time. Even then, this effect was likely the result of generational control of the nymphal stage which thus produced fewer adults over time. Nymphal control was excellent for Orthene, Vydate, and Regent. Yields were up to five times higher in the best treatments relative to the untreated control. Other effects were also documented for the best treatments which have additional positive impact on grower profitability: shorter plants (better defoliation), higher lint turnouts, less gin trash, and a lower seed index.
    • Short Staple Variety Trial, Greenlee County, 1998

      Clark, Lee J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Six short staple cotton varieties including two New Mexico acalas varieties and one advanced strain, an Australian varieties and two SureGrow varieties with higher yield potential were tested in this study. New Mexico Acala 1517-95 had the highest lint yield with a yield of 419 pounds of lint per acre. The average yield was about 400 pounds per acre lower than the 6 year average due to a cold spring and a four inch rain that fell in one hour in the middle of July. In addition to lint yields; percent lint, plant heights, plant populations and lint hvi values are shown. A lint yield comparison for 1993 through 1998 is included in this paper.
    • 1998 Seed Treatment Evaluations

      Norton, Eric C.; Silvertooth, Jeffrey C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      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 three Arizona locations; Maricopa, Marana, and Safford. Stand counts were taken after emergence at all three locations and percent emergence (PEM) was calculated. Significant differences in percent emergence due to seed treatments were observed in the both sample dates at Marana. Maricopa and Safford showed no statistically significant differences due treatment.
    • Cotton Defoliation Evaluations, 1998

      Silvertooth, Jeffrey C.; Norton, Eric R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      A field experiment was conducted near Marana, AZ in 1998 to evaluate the effectiveness of a number of defoliation treatments on Upland (var. Stoneville 474) cotton.. All treatments consisted of materials commercially available in Arizona. Results reinforce general recommendations regarding the use of low rates (relative to the label ranges) under warm weather conditions and increasing rates as temperatures cool. Defoliation treatments of Ginstar alone did a satisfactory job of defoliation and regrowth/topgrowth contol and were very similar to Dropp + Def combination treatments. Adding Prep to Ginstar in this experiment did not improve defoliation or topgrowth control.
    • Narrow Row Cotton Production in Vicksberg

      Knowles, Tim C.; Cramer, Roc; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Deltapine 458B/RR, Deltapine 5415RR, Deltapine 20B, and Deltapine 20 cotton varieties were planted on June 5 into narrow 15 inch wide rows. Populations ranged from 80,000 to 100,000 plants per acre. Seed cotton was stripper harvested on December 17. Although lint yields were somewhat low (1- 2 bale/acre) for this late planted cotton, we learned several important practices for effective narrow row cotton production systems, based on our first years experience in western Arizona.
    • Pima Cotton Regional Variety Trial, Safford Agricultural Center, 1998

      Clark, Lee J.; Carpenter, E. W.; Hart, G. L.; Nelson, J. M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Sixteen long staple varieties were tested in a replicated small plot trial on the Safford Agricultural Center in Graham county at an elevation of 2950 feet. The highest yielding variety in this study was OA 340 with a yield of 1021 pounds of lint per acre. It was followed by two other Olvey varieties yielding over 900 pounds per acre, including OA 322 and OA 361 (White Pima). In the adjacent regional short staple cotton trial were three interspecific hybrids from Hazera, an Israeli Seed Company. These hybrids grew like short staple cotton, but the fiber was more like the barbadense parent. These hybrids yielded from 1146 to 1091 pounds per acre. Their data is included at the bottom of the tables for comparison with the other long staple variety values. Yield and other agronomic data as well as fiber quality data are contained in this paper.