• Fruiting Distribution Patterns among Three Cotton Varieties under Irrigated Conditions

      Ozuna, S. E.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A field experiment was conducted at the UA Maricopa Agricultural Center (MAC) to determine the fruiting distribution patterns of two commonly grown Upland cultivars, DP 33b and DP 5415, and one American Pima cultivar, Pima S-7. Results indicate that cotton plants (G. hirsutum L. and G. barbadense L.) produce total yield at fruiting branches one through 18, with the majority of yield occurring at fruiting branches one through 12. Among fruiting branches one through 12, the majority of yield is occurring at fruiting positions one and two. These results indicate that the bulk of the yield is produced early in the season and declines as the season progresses
    • 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.
    • Pima Cotton Regional Variety Trial, Safford Agricultural Center, 1997

      Clark, L. J.; Carpenter, E. W.; Hart, G. L.; Nelson, J. M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      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 1997 was OA 325 with a yield of 746 pounds of lint per acre. It was followed by four other Olvey varieties yielding over 700 pounds per acre. 1997 was not a good Pima cotton year in this valley, weather problems early and insect problems late in the season both took their toll. Yields were more than 300 pounds lower than the previous year and 100 pounds less than in 1995. Yield and other agronomic data as well as fiber quality data are contained in this paper.
    • 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.
    • Diversity and Global Distribution of Whitefly-Transmitted Geminiviruses of Cotton

      Brown, J. K.; Silvertooth, Jeff; Department of Plant Sciences (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Geminivirus diseases of cotton are on the rise, worldwide, yet few have been studied in adequate detail to permit the implementation of rational approaches to disease control. The rising costs of managing the whitefly vector, coupled with substantial losses caused by geminivirus-incited diseases now hinder cotton production by requiring inputs that are beyond economic feasibility. The need for geminivirus disease resistant cultivars in diverse cotton producting areas and against different viral genotypes presents a new challenge. To meet this need, information about the identity, distribution, and relevant biotic characteristics of cotton -infecting geminiviruses is needed This project addresses this problem through the molecular analysis of the genomes of cotton-infecting geminivirus from cotton throughout the world Here, sequence similarities of the coat protein gene and of the non-coding IR/CR involved in regulating virus replication and transcription were examined by comparative sequence analysis to achieve virus identification. This is the first effort to determine virus identity and to map the distribution of geminiviruses on a global basis. The outcome of this effort will be a data base containing biotic and molecular information that will permit rapid and accurate geminivirus identification, and the selection of relevant viral species for development of cotton cultivars with disease resistance to the geminiviruses specific to individual production areas.
    • 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.
    • 1997 Cottonseed Variety and Treatment Evaluation

      Knowles, Tim C.; Wakimoto, Del, 1947-; 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.
    • 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.
    • 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.
    • 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.
    • Telone II® Following Grain Rotation for Nematode Control?

      Husman, S. H.; McClure, M. A.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Nine field trials were conducted between 1994 and 1997 in Buckeye and Gila Bend, Arizona to determine the effect of soil fumigation with Telone II on the yield of cotton following rotation with Durum wheat. Telone was shank injected at two or more rates (0, 3, or 5 gal/acre) in fields previously maintained with a cotton-wheat-summer/winter fallow rotation. Eight fields were planted to Upland and one field to Pima cotton. Eight of the nine studies resulted in a statistically significant lint yield increase with the 5 gallon rate compared to the untreated check. Seven of the nine studies resulted in a positive net economic return on investment ranging from $0.78/acre to $103.29/acre. In one trial where all three rates were compared, yield at the 5 gallon rate was increased 141 lint lbs/ac compared to the 3 gallon rate which did not differ from the control.
    • Layby Mexican Sprangletop Control with Select (Clethodim) and Antagonism Resulting from Staple (Pyrithiobac Sodium) and Select Tank Mixed

      Knowles, Tim C.; McCloskey, Bill; Keavy, Mike; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Late emerging summer annual grassy weeds such as Mexican sprangletop can stain cotton lint resulting in price discounts for color at harvest. Cyanizine (Bladex) is commonly applied layby for grassy weed, morningglory, and pigweed control, however use of this herbicide will be phased out by 2002 with rate reductions beginning in 1998. Clethodim (Select) herbicide was evaluated as an alternative to cyanizine for layby grassy weed control, plus the antagonistic effect of tank mixing Select with Staple herbicide was examined in Parker Valley, AZ during the 1997 cotton growing season.
    • 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.
    • 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.
    • Agronomic Evaluations of Transgenic Cotton Varieties

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Several field experiments were conducted in many of the cotton growing areas of Arizona in 1997 for the purpose of evaluating agronomic characteristics of many new transgenic Upland cotton varietie. In many cases, the new transgenic lines were compared directly with their recurrent (non-transgenic) parents. Evaluations were carried out by collecting plant mapping data from each variety on a regular 14 day interval throughout the season and relating the resultant information to established baselines for Upland cotton in Arizona. Lint yield measurements were also taken on each variety at all locations. Results indicate that all transgenic lines tested are very similar to their recurrent parents in terms of growth, development, and yield Some subtle differences were noted but they were very slight and should impact management of the varieties significantly in comparison to their recurrent parents.
    • IPM/BMP Practices in Arizona Cotton

      Baker, Paul B.; McCloskey, William B.; Sherman, Will; Dennehy, Timothy D.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Arizona cotton growers were surveyed regarding the importance of Integrated Pest Management (IPM) and Best Management Practices (BMP). Telephone surveys reached 249 individuals over a ten-day period. The survey asked growers to rate the importance of each IPM/BMP tactic on a scale of 1 (not important) to 5 (very important). Of the 14 practices /tactics listed for IPM, eight had significant chi-square values. These included scouting, crop rotation, variety selection, petiole testing for nitrogen, pheromone use, equipment calibration, and stalk destruction. Of the eight practices /tactics listed for BMP, six had significant chi -square values. These included crop rotation, timing and splitting of nitrogen applications, petiole testing, time of planting and variety selection for specific suppression (Bt cotton). In general, whether it was an IPM, weed management, or a BMP practice/tactic, the growers scored a majority of the tactics as important. It could be inferred from the growers' responses that they agree that the practices listed as important were, in fact, important grower practices.
    • 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).
    • Evaluation of B. T. Cotton Deployment Strategies and Efficacy against Pink Bollworm in Arizona

      Simmons, A. L.; Dennehy, T. J.; Tabashnik, B. E.; Antilla, L.; Bartlett, A.; Gouge, D.; Staten, R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A multi- agency team in Arizona in 1997 evaluated B.t. cotton deployment strategies in a large field trial; conducted statewide monitoring of pink bollworm (PBW) susceptibility to the Cry1Ac endotoxin, and established a Rapid Response Team that investigated claims of unacceptable performance of B.t. cotton. Though needing further evaluation, in-field refuges of one row of non-B.t. cotton for each five rows of B.t. cotton showed promise as an alternative to the current recommendation of external refuges for planting B.t. cotton. Preliminary results of statewide monitoring showed that four field populations were more susceptible to Cry1Ac than were two reference susceptible laboratory strains. A strain of PBW previously reported to be resistant to CrylAc was confirmed to be significantly less susceptible to this toxin than were the two susceptible laboratory strains or the four field populations tested. The Rapid Response Team, based at the Arizona Cotton Growers Association, investigated nine reports of unusual larval survivorship in B.t. cotton. Only one of these, which has been placed in culture, was confirmed to have resulted in substantial numbers of large larvae surviving in bolls of putatively B.t. cotton. Further investigations of this population and the plants from which it was derived are underway.
    • Nitrogen Management Experiments for Upland and Pima Cotton, 1997

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Two field experiments were conducted in Arizona in 1997 at two locations (Maricopa and Marana). The Maricopa experiment has been conducted for eight consecutive seasons, the Marana site was initiated in 1994. The purposes of the experiments were to validate and refine nitrogen (N) fertilization recommendations for both Upland and Pima cotton. The experiments each utilized N management tools such as pre- season soil tests for NO₃⁻-N in- season plant tissue testing (petioles) for N fertility status, and crop monitoring to ascertain crop fruiting patterns and crop N needs. At each location, treatments varied from a conservative to a more aggressive approach of N management. Results at each location revealed a strong relationship between the crop fruit retention levels and N needs for the crop. This pattern was further reflected in final yield analysis as a response to the N fertilization regimes used. The higher, more aggressive, N application regimes did not benefit yields at any location.
    • 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.