• Aflatoxin Contamination of Bt and Non-Bt Cottonseed

      Knowles, Tim C.; Wakimoto, Vic; Wakimoto, Del; Keavy, Mike; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Transgenic Bt cotton varieties that are resistant to pink bollworm should sustain less feeding damage to bolls and cottonseed, compared to non-Bt varieties that are more susceptible to feeding damage by pink bollworm larvae. Prior to boll opening, the aflatoxin producing fungus Aspergillus flavus cannot penetrate undamaged cotton bolls. Thus resistance to pink bollworm could result in reduced aflatoxin contamination under high pink bollworm pressure. Cottonseed aflatoxin levels of Bt and non-Bt varieties were compared at various planting and harvest dates. Bt and non-Bt cotton varieties had similar cottonseed aflatoxin levels. Long season production systems favored high cottonseed aflatoxin levels, compared to short season production systems, regardles of the cotton variety grown.
    • Fungicide Treatment and Varietal Effects on Alternaria Leaf Spot of Pima Cotton

      Olsen, Mary W.; Clark, Lee; Moser, Hal; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      The effect of foliar treatments for prevention of Alternaria leaf spot was evaluated in the field on six varieties of Pima cotton. Disease was significantly reduced by protective sprays of mancozeb and micronized sulfur but not by foliar applications of urea in trials at the University of Arizona Safford Agricultural Center in Safford, AZ. Treatments had no significant effects on yields. Significantly fewer lesions developed on Pima variety UA 4 than on the other varieties. Disease pressure was relatively light, and even though scheduled preventive sprays with mancozeb were effective, fungicide applications probably would not increase yields under the environmental conditions of this experiment.
    • Non-chemical Control of Cotton Seedling Damping-off in the Field

      Misaghi, I. J.; Heydari, A.; Zoki, K.; Silvertooth, Jeff; Department of Plant Pathology, University of Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      We conducted four field trials in April 1995 and 1996 in Arizona to compare the effectiveness of the following treatments to reduce cotton seedling damping-off incidence: 1) a soil drench of an isolate of the bacterium, Burkholderia cepacia (DI), recovered by us from cotton plants; 2) isolate D1 barley meal formulation; 3) Deny® seed treatment (a peat moss -based formulation of another isolate of B. cepacia, CCT Corp. Carlsbad, California); 4) Deny® soil drench; 5) Kodiak® seed treatment (a formulation of the bacterium, Bacillus subtilis, Gustafson Inc., Dallas, Texas); 6) a mixture of three fungicides Metalaxyl, Triadimenol, and Thiram seed treatment; and 7) a mixture of Metalaxyl, Triadimenol, Thiram, and Kodiak® seed treatment. Except for DI, the other products are being marketed for the control of cotton seedling damping-off Only DI soil drench and a mixture of the three fungicides seed treatment increased cotton stand significantly (P ≤ 0.05) in three of four field trials.
    • 1997 Cottonseed Variety and Treatment Evaluation

      Knowles, Tim C.; Wakimoto, Del; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Three upland cotton varieties (Deltapine 5415, Stoneville 474, and SureGrow 125) were subjected to three seed treatments (non or control, standard commercial triple treated, and standard commercial plus Prevail added to the hopper box at 1 lb product /100 lb cottonseed) to determine seed germination and vigor in a Mohave Valley field prone to Rhizoctonia infection of cotton seedlings.
    • Survey of Cotton Weeds and Weed Control Practice in Arizona Upland Cotton Fields

      McCloskey, William B.; Baker, Paul B.; Sherman, Will; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, AZ; Department of Entomology, University of Arizona, Tucson, AZ; National Agricultural Statistics Service, USDA, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      The distribution of weed species and the herbicides and cultural practices used to control weeds in Arizona cotton fields were surveyed in 1995 and 1996. The most common weeds were purple nutsedge, bermudagrass, annual morningglory, Palmer amarnath, Wright groundcherry, common purselane, yellow nutsedge and Johnsongrass. The average statewide cost for hand weeding in 1995 was reported as $27.87 per acre in addition to other weed control costs. Statewide, most growers used preemergence herbicides before or at planting and used pre- and post-emergence herbicides later in the season. Most of these applications were broadcast applications suggesting that many of the postemergence herbicide applications were layby applications. Preemergence herbicides (usually applied preplant incorporated) such as Treflan, Prowl, and Prometryn were more commonly used than postemergence herbicides. Statewide, few growers banded preemergence herbicides or used electro- hydraulic quick-hitch guidance systems and in-row weeding tools with their cultivators.
    • Preliminary Study of Cotton Weed Control Strategies Using Over-The-Top Herbicides

      McCloskey, William B.; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A study was conducted at the Maricopa Agricultural Center to compare various cotton weed control programs that combined the use of the over-the-top herbicides Buctril, Roundup Ultra and Staple with reduced or eliminated preemergence herbicide applications in dry planted cotton. Roundup Utra provide superior large seedling Palmer amaranth control compared to Buctril or Staple. The yield and end of the season weed control data showed that BXNBuctril and Staple weed control strategies require the application of a dinitroaniline herbicide prior to planting. The data also suggest that a band application of Prowl in combination with timely postemergence Buctril or Staple applications would be just as effective as preplant incorporated application of Prowl. In contrast to the Buctril and Staple herbicide treatments, the end of the season weed control ratings and seed cotton yield were the same for all of the Roundup Ready cotton treatments suggesting that Roundup Ready cotton weed control strategies do not necessarily require a dinitroaniline herbicide (Prowl or Trejlan) application prior to planting.
    • Field Determination of Permanent Wilting Point

      Norton, E. R.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      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 (PA its 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 two 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 at the Maricopa location.
    • Comparison of the Two Methods for the Analysis of Petiole Nitrate Nitrogen Concentration in Irrigated Cotton

      Smith, J. H.; Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A study was conducted in Arizona in 1997 with the objective of analyzing the accuracy of a recently developed portable nitrate meter (Cardy meter) to effectively measure petiole nitrate - nitrogen (NO₃-N) in irrigated cotton (Gossvpium sue.). This task was accomplished by performing correlation and linear regression analyses on NO₃-N concentrations of cotton petiole sap, as measured by the Cardy meter, against the standard procedure NO₃-N analysis, as measured by an ion selective electrode (ISE). Results revealed that the NO₃-N concentrations of petiole sap were highly correlated with dried petiole NO₃-N (pearson correlation coefficient = 0.96, P < 0.0001). A regression equation with an r² = 0.92 was derived: Y = 9.96X - 1170.86, where X and Y are NO₃-N in petiole sap (ppm) and dried petioles (ppm), respectively. These results suggest that the sap analysis using the Cardy meter is a potentially valuable tool to monitor the in-season N status of irrigated cotton.
    • Evaluation of a Feedback Approach to Nitrogen and Pix Applications, 1997

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A single field experiment was conducted in 1997 at Marana, AZ to compare a scheduled approach (based on stage of growth) versus a feedback approach (based on growth parameters) to both nitrogen (N) and mepiquat chloride (P1X) 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 for Arizona growing conditions. Scheduled and feedback FIX applications were made for a total of 0.75 and 1.50 pt./acre, respectively, with the scheduled treatments being initiated earlier in the fruiting cycle (early and peak bloom). Feedback PIX treatments consisted of a single 0.75 pt./acre application near peak bloom (approx. 2000 heat units after planting, HUAP, 86/55 °F threshold). Scheduled applications of fertilizer N totaled 150 lbs. N/acre from two applications and feedback N treatments received a total of 100 lbs. N/acre from two applications. Treatments consisted of all combinations of scheduled or feedback applications of both N and PIX. The highest lint yields were from treatments receiving PIX applications, with significant differences (P ≥ 0.05) between a check treatment (with no FIX applications) and several other treatments that did receive PIX applications. If FIX was applied, there were no significant differences between the scheduled or feedback approach. Applications of PIX in relation to increasing HNRs (feedback approach) are demonstrated and reinforced in this study.
    • Side-dress Temik® Effects on Lint Yields

      Husman, Stephen H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Temik 15G was side-dressed at a rate of 7 lb./acre and 14 lb./acre and compared to an untreated check in 4 experiments in 1996 and 1997 in Buckeye, Az. Treatments were made just prior to early bloom. Lygus counts were taken using a sweep net on weekly intervals for four to six weeks post application. A net positive return on investment (ROI) ranging from $34.79/acre to $48.19/acre was realized in three of the four experiments with the seven lb./acre rate. One experiment resulted in a net economic loss of $24.84. A net positive ROI was experienced in two of the four experiments ranging from $23.31 to $50.11 using the fourteen lb./acre Temik rate. Two of the four experiments resulted in a net loss ranging from $28.28 to $93.27 using the fourteen lb./acre rate. It appears that lint yield increase responses are due in part to a plant response to Temik, not necessarily related to lygus density as evidenced in part by the lack of measured sweep count populations.
    • Foliar Fertilizer Evaluation on Upland Cotton, 1997

      Silvertooth, J. C.; Norton, E. R.; Ozuna, S. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A single field experiment was conducted in 1997 at the University of Arizona Yuma Valley Agricultural Center. The purpose of the experiment was to evaluate foliar applications of Macro Sorb (L form amino acids) and KeyPlex (chelated micronutrients and alpha keto amino acids) foliar fertilization materials on Upland cotton. Treatments consisted of various rates and times of application of the foliar materials based upon manufacturer recommendations. Results from this single experiment revealed no differences among treatments with respect to in-season plant measurements, tissue N concentrations, or lint yield.
    • Spatial Analysis of Aspergillus flabus S and L Strains

      Orum. T. V.; Bigelow, D. M.; Cotty, P. J.; Nelson, M. R.; Silvertooth, Jeff; Department of Plant Pathology, University of Arizona, Tucson, AZ; USDA/ARS/SRRC, New Orleans, LA (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      The distribution of S and L strains of Aspergillus flavus is more stable than previously realized. Analysis with GIS/geostatistics shows that patches of similar S strain incidence persist over years. This information will be exceptionally useful to programs involved with or planning large-scale treatments to reduce aflatoxin contamination because it can be used to spatially focus treatments.
    • 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), 1998-04)
      This is a continuing report on the effects of over -irrigation in cotton production. Started in the Spring of 1995, this study uses drainage lysimeters to study the impact of over-irrigation on nitrate leaching losses. Furthermore, yield and other growth components are monitored to see what effect, if any, the over-irrigation has. The study was initiated at the Maricopa Agricultural Center, Maricopa, Arizona. The drainage lysimeters used 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, two 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 three 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 1.5 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, 940 lb./acre of lint in 1996 and 1300 lb./acre in 1997. Cumulative drainage was 8 inches in lysimeter one and 28 inches in lysimeter two. Nitrate losses for the three years totaled 126 lb. N/acre for lysimeter two and 72.5 lb. N/acre for lysimeter one.
    • 1997 Low Desert Upland Cotton Advanced Strains Testing Program

      Husman, S. H.; Silvertooth, J. C.; Clark, L.; Nelson, J.; Knowles, T.; Wegener, R.; Johnson, K.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Upland cotton advanced strains and commercial check comparison varieties were evaluated in replicated field studies at five locations in 1997. The test sites include Parker, Az., Gila Bend, Az., Buckeye, Az., Maricopa, Az., and Safford, AZ. Ten seed companies submitted a maximum of five advanced strains entries. Three commercial check varieties were used at each site for comparison purposes and included DPL 5415, SG 125, and STV 474.
    • Pima Regional Variety Test at the Maricopa Agricultural Center, 1997

      Hart, G. L.; Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Eighteen 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 population and fiber property data are presented in this report.
    • Correlation between Early Season Insecticide Control of Pink Bollworm and Other Pests and Subsequent Whitefly Applications near Gila Bend, AZ, 1997

      Jech, L. E.; Husman, S. H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Cotton pesticide application histories in the Gila Basin were followed from 27 April through 20 September. The main interest was the effect of early season applications to control pink bollworm, Pectinophora gossypiella, and other pests on subsequent whitefly applications. Categories explored include, transgenic and non transgenic cotton, planting dates, and location within the valley. Regression analysis shows a significant effect due to the early season control for either P. gossypiella, or other pests (P > 0.009) but lower for them together (P > 0.026). Early applications for either PBW or other pest resulted in increased application for whitefly.
    • Irrigation Efficiencies and Lint Yields of Upland Cotton Growth at the Maricopa Agricultural Center, 1997

      Sheedy, Mike; Watson, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      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. This year there was a lint yield response to the different irrigation efficiencies, and a slight difference in yield between the two varieties. Lint yields were significantly lower in the 95% irrigation efficiency plots. Lint Yields ranged from 1448 # lint /acre (SG125 at 75%) to 1220 # lint/acre ( DP5409 at the 65% irrigation efficiency).
    • 1997 Season Update on Resistance of Arizona Whiteflies to Synergized Pyrethroid and Select Non-Pyrethroid Insecticides

      Dennehy, Timothy J.; Williams, Livey III; Li, Xiaohua; Wigert, Monika; Silvertooth, Jeff; Department of Entomology, The University of Arizona; Extension Arthropod Resistance Management Laboratory, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A whitefly resistance crisis in Arizona in 1995 prompted the development of a resistance management strategy in 1996 that recommended maximal once per season use of two insect growth regulators, pyriproxyfen (Knack®) and buprofezin (Applaud®), and limited and delayed use of synergized pyrethroid insecticides in cotton. Statewide monitoring of whitefly resistance has shown that implementation of this strategy has substantially reduced whitefly resistance to the synergized pyrethroids and has also resulted in increased susceptibility to key non pyrethroid insecticides. Having benefited from two years of success with this strategy, the Arizona cotton industry now faces the question of whether it can be sustained as pyriproxyfen and buprofezin gain additional registrations for use against whiteflies in vegetables, melons and glasshouse crops.
    • 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), 1998-04)
      Green bolls (100/field) were sampled from the uppermost internodes within adjacent fields of Bt (Deltapine 33B) and non-Bt (Hyperformer HS 44) cotton experiencing severe pink bollworm pressure late in the growing season. Average top crop lint yield reductions ranging from 30 to 70% were observed in the uppermost bolls of the non-Bt cotton variety. Average top crop lint yield reductions ranging from 0 to 40% were observed in the uppermost bolls of the transgenic Bt cotton variety.
    • Infection of Sorghum Varieties by the Cotton Root-knot Nematode, Meloidogyne incognita

      McClure, M.; Husman, S.; Schmitt, M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Twentythree varieties of sorghum, Sorghum bicolor, were evaluated for susceptibility to the cotton root -knot nematode, Meloidogyne incognita race 3. Eggs per gram of root were used as a measure of nematode reproduction and host susceptibility. The nematode reproduced on all varieties tested Mean egg counts were lowest on the varieties Northrup King (NK) KS-737, MF.; NK 1580,M; NK Ks-735 M.F.; NK 714Y MF.; NK Lt. Bronze X 609 M; Ciba-NK C-1506, M; and Pioneer 8877, but these varieties are still considered to be hosts capable of sustaining or increasing nematode populations in cotton fields. All varieties were better hosts than cotton.