• 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.