• Mepiquat Chloride Effects on Irrigated Cotton in Arizona

      Norton, E. J.; Silvertooh, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      A series of experiments have been conducted from 1988 to 1999 at various locations across the cotton producing regions of Arizona to evaluate mepiquat chloride (MC) applications in terms of plant growth and yield. These experiments were designed to evaluate MC under three application regimes. These regimes included low rate multiple applications, late season applications, and a feedback vs. scheduled management of MC and nitrogen (N) applications. The objective of this summary (including a total of 31 site-years) is to determine which of these three application regimes offer the greatest opportunity for a positive lint yield response to MC. Stability analysis was conducted by regressing the treatment mean lint yield against the environmental mean for each application regime. Results from the stability analyses revealed that the most viable method of application is a feedback approach for both MC and fertilizer N. The most reliable technique associated with plant assessment in a feedback approach was the height to node ratio (HNR) to indicate vegetative tendencies for determining the appropriate rate and timing of MC applications.
    • The New U. S. - China Trade Agreement and Arizona Cotton

      Ayer, Harry; Frizvold, George; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      Gaining greater access to export markets, particularly Asian markets, is important to Arizona cotton producers. Over 80 percent of Arizona’s cotton shipments are exports, roughly double the U.S. average. Asian countries typically account for half of world cotton imports. Relative to the rest of the United States, Arizona (along with California) has a location advantage supplying these markets. In November 1999 the United States and China signed a trade agreement to reduce China’s trade barriers and win U.S. support for China’s entry into the World Trade Organization (WTO). According to recent USDA projections, the agreement would increase China’s net cotton imports by $359 million when fully implemented in 2005 and by $328 million per year between 2000-09. Political uncertainty surrounds the timing of China’s accession to the WTO, however, and China’s return to cotton net-importer status could be delayed by Chinese policies to draw down their large accumulation of cotton stocks.
    • Nitrogen Management Experiments for Upland and Pima Cotton, 1999

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      Two field experiments were conducted in Arizona in 1999 at two locations (Maricopa and Marana). The Maricopa experiment has been conducted for nine consecutive seasons, the Marana site was initiated in 1994. The purposes of the experiments were to validate and refine nitrogen (N) fertilization recommendations for Upland 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. In 1999, fruit retention levels were low and crop vigor was high at the Maricopa site. As a result, even slight increases in N fertilization and crop vigor translated into lower yield.
    • Performance of Bollgard II® Upland Cotton Strains in Arizona

      Moser, H. S.; Silvertooth, Jeff; University of Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      Experimental strains containing the Bollgard II® gene construct have been developed in upland cotton through transformation of DP50B. We evaluated the field performance of two of these new strains at four locations in Arizona. Lint yields of these two lines compare favorably with the parent material used to develop the lines (DP50B), but are significantly lower than other conventional and transgenic varieties that are adapted to Arizona. Fiber quality was not compromised in the Bollgard II strains. In fact, one line, 15813, produced fiber that was of superior quality to DP50B. One of the lines (15985) was similar to DP50B for all traits measured in this test. These results show that the Bollgard II gene construct does not, in itself, compromise agronomic performance. Thus, it should be possible to successfully place Bollgard II into other varieties that are adapted to Arizona in order to produce an agronomically superior variety with the added benefit of the Bollgard II technology.
    • Pesticide Use in Arizona Cotton: Long-Term Trends and 1999 Data

      Agnew, G. E.; Baker, P. B.; Silvertooth, Jeff; Pesticide Information and Training Office (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      Arizona pesticide use, as reported on the Department of Agriculture's form 1080, can be summarized to provide a rich picture of pest management in Arizona cotton. Limitations in the pesticide use reporting system complicate the process but do not undermine results. Overall pesticide use decreased over the period 1991 to 1998 despite a peak during the whitefly infestation of 1995. Decreases in insecticide use are responsible for most of the reduction in pesticide use. Recently released 1999 data indicates that reductions continued. Comparison of the composition of pesticide applications between 1995 and 1998 reflect the changes in pest control efforts. A new "target pest" category on the 1080 provides an even richer picture of pest management practices in Arizona cotton.
    • Pima Cotton Regional Variety Trial, Safford Agricultural Center, 1999

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      Thirty 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 Hazera 83-208 with a yield of 1272 pounds of lint per acre. This interspecific hybrid from Israel yielded nearly 300 pounds per acre more lint than the next closest variety. The average yield in the trial was lower than in the previous year’s study. Yield and other agronomic data as well as fiber quality data are contained in this paper.
    • Pink Bollworm Egg Infestations and Larval Survival in NuCOTN 33b and Deltapine Cottons in Arizona

      Henneberry, T. J.; Forlow Jech, L.; de la Torre, T.; Faulconer, S; Hill, J. J.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      The gene for the Bacillus thuringiensis var. kurstaki (Berliner) insect toxic protein is a new advance in technology for pink bollworm (PBW), Pectinophora gossypiella (Saunders), control. We conducted studies in 1999 to investigate grower concern for reduced efficacy of NuCOTN 33b (Bt cotton) (Monsanto Company, St Louis, MO) in late-season because of breakdown or non-expression of the toxic protein. We compared the susceptibility of Bt and Deltapine 5415 (Monsanto Company, St Louis, MO) (non-Bt) cotton bolls to PBW at periodic intervals during the first and second cotton fruiting cycles. We placed >200 PBW eggs per boll on the inside surface of bracts of susceptible immature cotton bolls. The artificially infested bolls were later harvested and examined for evidence of PBW infestation. High percentages of both Bt and non-Bt cotton bolls had numerous larval entrance holes in the carpel walls of the bolls. Less than 1% of the Bt cotton bolls and over 70% of the non-Bt cotton bolls were found with living PBW larvae. Bt cotton bolls of the late-season second fruiting cycle were as resistant to PBW infestation as Bt cotton bolls of the first fruiting cycle.
    • Planting Date Effects on Soil Temperature, Crop Growth, and Yield of Upland Cotton, 1999

      Silvertooth, J. C.; Norton, E. R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      A field study was conducted in 1999 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 eight Upland varieties. Soil temperature effects associated with date of planting and method of planting (dry or wet planting) were also evaluated in relation to soil temperature at the depth of seed placement. Planting dates ranged from 28 April to 20 May and 821-1157 heat units accumulated since Jan 1 (HU/Jan 1, 86/55o F thresholds). Lint yields generally declined with later dates of planting for all varieties. Soil temperatures associated with the dry planting method, which requires a water-up irrigation, experienced much wider diurnal variations, had slightly lower mean temperatures, and were more strongly coupled to ambient air conditions. Thus, dry planting methods impose more potential risk in terms of seedling stress. Overall, crop growth and development patterns or yield results were not significantly different between the planting methods. Either method can provide satisfactory results if managed appropriately.
    • Preliminary Investigations in Ultra-narrow Row Cotton, Safford Agricultural Center, 1999

      Clark, L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      A preliminary investigation was made in Ultra-narrow row cotton production on the Safford Agricultural Center to see if there was any promise in that technology for cotton producers in the high deserts of Arizona. Increases in plant populations to near 100,000 plants per acre in single lines, double lines and quadruple lines per bed were the goals of the study. In-season plant mapping to evaluate differences in plant growth characteristics were done along with yield measurements to evaluate differences. Yield increases were not seen with increases in plant populations in single row plantings nor in multiple row plantings.
    • Reduced Whitefly Infestations in Cotton Using a Melon Trap Crop

      Castle, S. J.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Lab (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      A second year of field experiments was completed in 1999 at MAC that explored the potential of using a melon trap crop to reduce whitefly infestations in cotton. The experimental design was altered from 1998 to gain isolation among treatment blocks by using 4 separate fields that helped to avoid the influence of one treatment upon the other. A consistent response of significantly fewer whiteflies in cotton planted within a surrounding melon trap crop, relative to the same area of cotton without the trap crop, was observed throughout the July- September sampling period. Better chemical management of whiteflies in the melons during the second season helped to reduce the large differential in whitefly densities between melons and cotton observed the previous year, but preferentially contributed to a greater differential observed between melonprotected cotton and unprotected cotton. Although the infestation buildup was delayed and the season-long densities of whiteflies in the melon-protected cotton were reduced, the action thresholds for treatment with IGRs were ultimately attained and exceeded. In the present management environment of perhaps only 1 IGR treatment per season, it is unlikely that the melon trap crop approach would provide acceptable control unless a grower was willing to tolerate lateseason whitefly densities higher than the current IPM recommendations.
    • Short Staple Variety Trial in Cochise County, 1999

      Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      The Acala and Upland Variety trials typically grown in Cochise County were combined into one study in 1999 and were planted on the Glenn Schmidt farm, in Kansas Settlement. Twelve varieties were tested including three New Mexico Acalas and one Interspecific Hybrid from Israel. The highest yielding variety in the trial was FM 989 with a yield near 1200 pounds of lint. It was also the highest yielding variety in the Cochise County trial in 1998. PM 1560 BG came in a close second with the Israeli varity (Hazera 151-208) and the two New Mexico varieties (1517-95 and 1517-99) yielding over 1100 pounds of lint.
    • Short Staple Variety Trials, Graham County, 1999

      Clark. L. J.; Carpenter, E. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      Two replicated on-farm short staple variety trials were planted in 1999. Twenty-two varieties were evaluated on the Claridge farm in Solomon and fifteen varieties on the Colvin farm near Ft. Thomas. Several new varieties were planted in these studies, including 2 transgenic varieties: DP 5690RR, BXN 16; 4 Israeli inter-specific hybrids and six other varieties seen for the first time. DP 35B was the highest yielding variety in the Claridge trial with BXN 47 a close second. Both varieties yielded over 1300 pounds of lint per acre. PM 1440 was the highest yielding variety in the Colvin trial with SG 747 and DP 5690RR following closely behind. These varieties yielded between 700 and 800 pounds of lint per acre. Other agronomic data from the varieties and HVI values from the lint are also included in this report.
    • Silverleaf Whitefly - Trichome Density Relationships on Selected Upland Cotton Cultivars

      Chu, C. C.; Natwick, E. T.; Henneberry, T. J.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      We studied silverleaf whitefly (SLW) and trichome density relationships on ten selected upland cotton cultivars: Deltapine #20B, 50B and 90B, NuCOTN 33B, Stoneville 474, Fibermax #819 and 832, Siokra L-23, and 89013-114 at Maricopa, in AZ, 1999. Whitefly and stellate trichome densities were counted on leaves on main stem leaf nodes #1, 3, 5 and 7 of each cultivar. Stoneville 474 had about 2-3 times more eggs, nymphs, and adults and also had 3-30 times more branched trichomes on abaxial leaf surfaces compared with the nine other cultivars. The top young leaves on node #1 had about 6 times more stellate trichomes compared with older leaves. However, the top young leaves also had reduced numbers of eggs and nymphs (23 and 1/cm2 of leaf disk, respectively) compared with older leaves. The results suggest that other factors, in addition to trichomes, at least for young terminal leaves, affect silverleaf whitefly population development.
    • Soil Test Calibration Evaluations for Phosphorus on Upland and Pima Cotton

      Thelander, A. S.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      Numerous field experiments were conducted at a wide range of sites in Arizona from 1988 through 1999 involving phosphate (P) fertilization of cotton (Gossypium spp.). A total of 21 site-years were used to study the effects of P on both Upland (G. hirsutum L.) and Pima (G. barbadense L.) varieties. The purpose of these experiments was to evaluate University of Arizona (UA) soil fertility guidelines with respect to soil test results (NaHCO3 extractable P) and to possibly fine-tune or calibrate these guidelines in relation to soil test P, applied P, and yield for common Arizona soils used in cotton production. Results from these experiments, based on soil test information, plant measurements, and lint yield showed no significant difference (P 0.05) due to treatments for all the studies with the exception of one P study conducted in Graham County in 1998 and another P study conducted in Pinal County in 1999. The 1998 Graham County site had a preseason soil test value of 7.6 ppm NaHCO₃ extractable P. The 1999 Pinal County site had a preseason soil test value of 3.0 ppm NaHCO3 extractable P. Analysis of yield results vs. soil P show that soil test P levels greater than 5 ppm are consistently sufficient for both Upland and Pima cotton. Yield results vs. applied P (lbs. P₂O₅/acre) for both Upland and Pima did not indicate a positive response over the rates of fertilization tested (20-160 lbs. P₂O₅/acre). Based on the results from these studies, the current UA soil fertility guidelines for P fertilization of cotton appear to be valid. Furthermore, the data indicates that the UA soil fertility guidelines may be further refined to provide the following categories: < 5 ppm = high probability of response to an added P fertilization; 6-10 ppm = medium probability of response to an added P fertilization; and > 10 ppm = low probability of response to an added P fertilization.
    • Susceptibility of Arizona Whiteflies to Chloronicotinyl Insecticides and IRGs: New Developments in the 1999 Season

      Li, Yongsheng; Dennehy, Timothy J.; Li, Xiaohua; Wigert, Monika E.; Silvertooth, Jeff; Extension Arthropod Resistance Management Laboratory, Department of Entomology, The University of Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      Whiteflies are serious pests of cotton, melons, and winter vegetables in Arizona’s low deserts. Successful management of whiteflies requires an integrated approach, a critical element of which is routine pest monitoring. In this paper we report findings of our 1999 investigations of resistance of Arizona whiteflies to insect growth regulators (IGRs) and chloronicotinyl insecticides. Whiteflies collected from cotton fields, melon fields and greenhouses were tested for susceptibility to imidacloprid (Admire/Provado), and two other chloronicotinyl insecticides, acetamiprid and thiamethoxam, and to two insect growth regulators (IGRs), buprofezin (Applaud) and pyriproxyfen (Knack). Contrasts of 1999 and 1998 results indicated increased susceptibilities, on average, to both imidacloprid and buprofezin of whiteflies collected from cotton. A cropping system study showed that whiteflies collected from spring melons had significantly lower susceptibility to imidacloprid than those collected from cotton or fall melons. The opposite was found for pyriproxyfen, to which whiteflies from cotton and fall melons had lower susceptibility than those from spring melons. As in 1998, whiteflies with reduced susceptibility to imidacloprid continue to be found in certain locations, particularly in spring melon fields and greenhouses. Results of our laboratory bioassays on susceptibility of Arizona whiteflies to chloronicotinyl insecticides provided evidence of a low order cross-resistance between imidacloprid, acetamiprid and thiamethoxam. Monitoring in 1999 provided the first evidence of reduced susceptibility of Arizona whiteflies to pyriproxyfen.
    • Upland Cotton Regional Variety Trial

      Moser, H.; Hart, G.; Clark, L.; Silvertooth, Jeff; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      Each year the University of Arizona conducts upland cotton variety tests to evaluate the performance of a diverse set of experimental lines and commercial varieties in Arizona. One such program is the Regional Variety Test (RVT). In 1999, we evaluated a total of 59 varieties at one or more locations in Arizona. These varieties were submitted to us for testing by 16 private seed companies and two public breeding programs. This report presents the results of the trials conducted at Maricopa, Marana, and Safford.
    • Use of Insect Growth Regulators and Changing Whitefly Control Costs in Arizona Cotton

      Agnew, G. Ken; Frisvold, George B.; Baker, Paul; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      In 1996, two Insect Growth Regulators (IGRs), pyriproxyfen (Knack®) and buprofezin (Applaud®) became available to Arizona cotton growers for control of whitefly, Bemisia argentifolii under a Section 18 EPA exemption. This study makes use of a section-level database to examine (a) factors explaining IGR adoption and (b) how adopters of IGRs altered their overall insecticide use to control whiteflies. IGR adoption can be explained to a large extent by location effects. Adoption was more likely on sections where an index of whitefly susceptibility to synergized pyrethroids was low and on sections with higher whitefly control costs in the previous year. Adoption was inversely related to local population density. On sections where growers adopted IGRs, expenditures on synergized pyrethroid and other whitefly-specific tank mix applications fell by $62.52 per acre. On sections with no IGR adoption, tank mix expenditures fell less, by $44.37 per acre. On adopting sections, net costs of controlling whiteflies fell by $29.62 per acre, or by over $11,000 per farm.
    • Weed Control in Arizona Ultra Narrow Row Cotton: 1999 Preliminary Results

      McCloskey, William B.; Clay, Patrick A.; Husman, Stephen H.; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, AZ; Maricopa County Cooperative Extension, University of Arizona, Phoenix, AZ; Pinal and Pima County Cooperative Extension, University of Arizona, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2000)
      In two 1999 Arizona studies, a preplant incorporated (PPI) application of Prowl (2.4 pt/A) or Treflan (0.75 lb a.i./A) followed by a topical Roundup Ultra (1 qt/A) application at the 3 to 4 true leaf cotton growth stage provided good weed control. At the University of Arizona Maricopa Agricultural Center field that had low density weed populations, a postemergence topical Staple (1.8 oz/A) application also provided good weed control was more expensive. At the Buckeye, Arizona study site, a PPI application of Prowl at a reduced rate (1.2 pt/A) was as effective as the full rate (2.4 pt/A) but a preemergence application of Prowl (2.4 pt/A) was not as effective as either of the PPI Prowl rates or PPI Treflan (0.75 lb a.i./A). A postemergence topical Staple application (1.8 oz/A) following the Roundup Ultra application did not significantly improve weed control. After one field season of experimentation and observation in Arizona UNR cotton, experience suggests that in fields with low to moderate weed populations, a PPI Prowl or Treflan application followed by a postemergence topical Roundup Ultra application will provide acceptable weed control in most fields. However, the presence of nutsedge or other difficult to control weeds may require two postemergence topical Roundup Ultra application prior to the four leaf growth stage of cotton. More research is needed to further explore weed control options in Arizona UNR cotton production systems.