• Upland Regional Cotton 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)
      Thirty four upland cotton varieties were grown 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 are presented in this paper.
    • Do PIX® Application Guidelines Change for Bt Cotton?

      Husman, Stephen H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Two PIX experiments were conducted on commercial cooperator sites in Waddell and Buckeye, Az in 1997 to evaluate the validity of the published University of Arizona (UA) PIX application guidelines for Bt cotton. Experimental treatments consisted of an untreated check, a calendar based application schedule (early bloom, peak bloom, cutout), and a feedback approach using plant growth measurements based on the UA PIX guidelines (height:node ratio, fruit retention). There were no significant yield differences at the Waddell site where height:node ratios and fruit retention values were above the optimum baseline season long, conditions not supportive of PIX applications. There was a significant yield decline at the Buckeye site between the untreated check and the calendar based treatment. Due to low plant vigor season long , there were no feedback based PIX applications. PIX applications under low vigor conditions can further compromise plant vigor and ultimately yield. The UA PIX application use guidelines are valid and should be used for both Bt and non -transgenic Upland cotton varieties.
    • 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.
    • Seasonal Distribution of Bemesia Honeydew Sugars on Pima and Upland Cotton Lint

      Henneberry, T. J.; Forlow Jech, L.; Hendrix, D. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Bemisia argentifolii Bellows and Perring populations were higher on Pima S-7 cotton compared with DPL 50 cotton. Higher numbers of mature open cotton bolls occurred earlier for DPL 50 compared with Pima S-7. Also, numbers of open bolls for DPL 50 peaked 8 to 14 days before Pima S-7 and decreased dramatically by 15 September reflecting termination of the first fruiting cycle in August In contrast the indeterminate fruiting pattern of Pima S-7 showed that numbers of open bolls per week declined gradually after the peak without a clear cut termination occurrence. About 95 and 80% of the open cotton bolls, of the Deltapine and Pima S-7 cottons, respectively, occurred by mid- September. This suggests that defoliation timing and early harvest can be important management tools to avoid sticky cotton. For upland cotton, extending the cotton season after 95% of the crop matured (≅ 15 September) resulted in development from non - sticky cotton to lightly- sticky cotton within 21 days following the occurrence of increasing whitefly populations after 15 September. Later fruiting and lack of a distinct end of the first cotton fruiting cycle probably precludes using early defoliation for long -staple Pima cotton. At harvest, thermodetector counts for all weekly harvests were greater than amounts found in lint for randomly selected 20 boll samples; and samples from all cotton picked from 4 m of row. This probably occurred because weekly picked cotton escaped rainfall and exposure and other weathering, in 1995 but not 1996, and machine - picked cotton contains more honeydew- contaminated leaf trash. Except in one instance, thermodetector counts and trehalulose and melezitose content in lint for all sampling methods were significantly correlated.
    • 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.
    • Marana Pima Test, 1997

      Hart, G. L.; Nelson, J. M.; Barney, Glen; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Nine pima cotton varieties were grown at Marana Agricultural Center as part of the national cotton variety testing program. Lint yield, boll size, lint percent, and plant population are presented in this report.
    • 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.
    • Cotton Virus Diseases

      Nelson, M. R.; Nadeem, A.; Ahmed, W.; Orum, T. V.; Silvertooth, Jeff; Department of Plant Pathology, University of Arizona, Tucson, AZ; Central Cotton Research Institute(CCRI), Multan Pakistan; Ayub Agricultural Research Institute(AARI), Faiselabad, Pakistan (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Virus diseases of cotton have historically been of only sporadic importance to global cotton production. Recent devastating epidemics in Pakistan and other areas have brought new awareness to the potential for disaster of a pathogen once considered to be of a minor importance. Under changing conditions this pathogen (cotton leaf curl virus) has emerged as a serious problem in Pakistan and India. Cotton leaf curl virus does not occur in the United States or the rest of the western hemisphere but recent experience worldwide is a reminder that pathogens, such as this geminivirus, can be moved easily from one part of the world to another and therefor we need to be aware of the potential impact of such pathogens on local crops.
    • Efficacy of Experimental Insecticides for Insect Control in Cotton Grown in the Low Desert Region of Arizona, 1997

      Kerns, David L.; Tellez, Tony; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Experimental insecticides were evaluated for control of lygus bugs relative to commercial standards in cotton. These products were also evaluated for activity towards whiteflies and pink bollworms. CGA293343 was not effective when used as a side-dress material at layby, but was effective toward whiteflies, and towards lygus at higher foliar rates. Regent, Vydate and Mustang + Thiodan were highly effective for lygus control, while EXP61096A and Mustang alone performed poorly. Against whiteflies, CGA293343, Acetamiprid, and Mustang + Thiodan were most efficacious, while Mustang alone and with Thiodan were most effective towards pink bollworms.
    • Efficacy of Experimental Insecticides for Whitefly Control in Cotton, 1996

      Kerns, David L.; Tellez, Tony; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Experimental insecticides were evaluated for control of sweet potato whiteflies relative to a commercial standard in cotton. Ni-25 provided excellent whitefly control and was equivalent to the commercial standard (Knack followed by Danitol + Orthene). Fenoxycarb + pymetrozine provided goodwhitefly control but seemed to require 2 sequential applications before control was equivalent to Ni-25. Diofenolan + pymetrozine appeared to be a slightly weaker treatment, but still provided acceptable whitefly control.
    • 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.
    • 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.
    • 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.
    • 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.
    • Short Staple Cotton Advanced Strains 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)
      Twenty five short staple advanced strains /varieties were grown in a replicated field on the Safford Agricultural Center in 1997. These included thirteen lines from Australia (including transgenic Bt lines), four lines from Georgia, five lines from NMSU, and two lines from Terra. The transgenic Australian lines dominated the trial with three of them yielding over 3 bales. The next nine varieties yielded over 2.5 bales per acre, they included six Australian variety, DP 90 (the standard variety) and an experimental from New Mexico. IF 1003 was the highest yielding non-transgenic variety in the trial. Much agronomic information is included in the paper as well as HVI values for each variety.
    • Effects of Cotton Ginning and Lint Cleaning on Sticky Cotton

      Henneberry, T. J.; Hendrix, D. L.; Perkins, H. H.; Silvertooth, Jeff; USDA, ARS Western Cotton Research Laboratory, Phoenix AZ; USDA, ARS, Cotton Quality Research, Clemson, SC (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      Ginning and lint cleaning effects on cotton stickiness were minimal but reduced amounts of trehalulose and reduced thermodetector counts occurred following each lint process Leaf trash from ginned seed cotton contained trehalulose and melezitose. Removal of leaf trash in ginning and lint cleaning probably accounts for some reduced lint stickiness.
    • 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.
    • Evaluation of Irrigation Termination Affects on Upland Cotton, 1997

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)
      A single field study was conducted in 1997 at the Maricopa Agricultural Center (1,175ft. elevation) to evaluate the effects of three dates of irrigation termination on the yield of a common Upland cotton variety (DP NuCOTN 33b). Planting date was 9 April (668 HU /Jan 1 86/55° F thresholds. Three dates of irrigation termination (IT1, IT2, and IT3) were imposed based upon crop development into cut -out. The earliest irrigation termination date, IT1 (7 August) was made as early as possible in an attempt to provide sufficient soil - water 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 20 August, and provided one additional irrigation over IT1. The final (IT3) date was 17 September, which was staged so that soil moisture would be sufficient for development of bolls set up through the last week of September and provide full top-crop potential. Lint yield results revealed no differences among any of the IT treatments. Mirconaire values increased slightly with later IT dates.
    • Review of the 1997 Arizona Cotton Season

      Silvertooth, Jeffrey C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1998-04)