• Effect of Norflurazon (Zorial Rapid 80®) Mixed with Pendimethalin (Prowl®) and Prometryn (Caparol®) on Cotton Stand Establishment and Yield

      McCloskey, William B.; Dixon, Gary L.; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      The effect on cotton stand establishment and seed cotton yield of various rates of norflurazon applied in combination with pendimethalin or both pendimethalin and prometryn was determined in field studies conducted at the Maricopa Agricultural Center in 1994 and 1995 in a sandy loam soil. Cotton stand counts were highest when only pendimethalin was applied or when no herbicide was used. Tank mixing prometryn with pendimethalin did not significantly reduce plant populations. Tank mixing increasing amounts of norflurazon with pendimethalin resulted in decreasing plant populations in both the wet and the dry plant experiments. Tank mixing increasing rates of norflurazon with both pendimethalin and prometryn caused a similar decline in plant populations in both the wet and the dry plant experiments. The symptoms of dying cotton seedlings and the stand count data indicated that notflurazon was the component of the tank mixtures that caused seedling mortality. The effect of the herbicide treatments on seed cotton yields was much less than on stand counts, but the same trends discussed above were evident. However, at the label rate for norflurazon in coarse textured soils, 0.5 lb a. i./A, seed cotton yields were not significantly reduced. The smaller effect of the herbicide treatments on seed cotton yields was due to the bush type nature of DPL 5415 and increased growth of surviving plants when plant populations were reduced. The data indicates that yield losses were not significant unless plant populations were reduced below about 20,000 to 25,000 plants /A.
    • How the Quick Hitch Guidance Systems Work and Their Practical Applications

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      This article explains the operation of the two types of quick hitch guidance systems on the market. Techniques for farming with precision guidance are offered.
    • How to Mechanically Remove Weeds from the Row

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      This article offers practical advice on in-row weeding techniques and tooling setups.
    • Monitoring and Management of Whitefly Resistance to Insecticides in Arizona

      Dennehy, T. J.; Williams, Livy III; Russell, June S.; Li, Xiaohua; Wigert, Monika; Silvertooth, Jeff; Extension Arthropod Resistance Management Laboratory (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Monitoring of whitefly resistance in the major cotton producing areas of Arizona confirmed the presence of an over 100 fold resistance to the mixture of Danitol® + Orthenem (fepropathrin + acephate). Strong evidence was found of cross-resistance affecting the other principle pyrethroid insecticides used to control whiteflies (Asana®, Capture® Karate®). Susceptibility to Ovasyn® varied widely in leaf -disk bioassays; lesser variation was observed in whitefly susceptibility to endosulfan. A provisional resistance management strategy (IRM) for Arizona whiteflies was formulated and evaluated in a 200 acre field trial in 1995. A key element of the strategy was diversifying as much as possible the insecticides used against whiteflies. Contrasts of this (rotation) strategy with a more conventional (less diverse) regime showed that rotation slowed but did not prevent resistance from developing. By seasons end both the IRM and conventional plots had very high and comparable levels of resistance to Danitol® + Ortliene®. This large field trial illustrated clearly the seriousness of the whitefly resistance problems faced in Arizona. It showed that whitefly populations cannot be managed effectively solely with the products currently registered for this purpose in Arizona. The large shift to lower susceptibility took place with as few as 3 insecticide treatments. In concert, our field art laboratory results indicated unequivocally that Arizona growers will be forced by resistance to greatly reduce reliance on pyrethroid insecticides in the future. This underscores the urgency for obtaining approval of novel new insecticides for whitefly control and for deploying new products within the framework of a resistance management strategy that limits their use.
    • Response of Cotton to Precision-Guided Cultivation and DSMA in a Dense Stand of Purple Nutsedge

      Thacker, Gary W.; McCloskey, William B.; Silvertooth, Jeff; UA Cooperative Extension, Pima County, Tucson, Arizona; Department of Plant Sciences, University of Arizona, Tucson, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      Close cultivation (within 1.5 inches of the cotton drill row) accomplished with an electro-hydraulic machine guidance system and an early season application of the herbicide DSMA were evaluated for purple nutsedge suppression in cotton. There were no significant differences in the cotton plant mapping data collected mid - season except that there was significantly less boll retention on the second fruiting branch in the precision cultivator treatments that may have been caused by root pruning during the second precision cultivation that could have shocked the cotton. There were significant differences in seed cotton yield with the precision cultivator treatments yielding more than the standard cultivator treatments. There was an opposing yield trend with the use of DSMA; DSMA tending to be beneficial with the precision cultivator and detrimental with the standard cultivator. We cannot explain this opposing trend. We regard our results as preliminary until we gain more experience with precision-guided cultivators in dense stands of nutsedge.
    • Weed Control in Roundup Ready® Cotton: Preliminary Experiments

      McCloskey, William B.; Dixon, Gary L.; Moffett, Jody E.; Silvertooth, Jeff; Department of Plant Sciences, University of Arizona, Tucson, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 1996-03)
      The efficacy of Roundupm herbicide for the control of common Arizona weeds in Roundup Ready® cotton was evaluated in field studies conducted at the Maricopa Agricultural Center in 1995. Promising results were obtained with 1 lb a.i./A (1 quart/A) over-the-top band applications of Roundup when cotton had 1 to 2 true leaves followed by a second, "sloppy", post-directed application ofRoundup at 1 lb a.i./A when cotton had 4 to 5 true leaves. Excellent control of small Palmer Amaranth, Wright Groundcherry, and annual morningglory seedlings was obtained with each 1 lb a.i./A Roundup application in the broadleaf weed study. The two sequential 1 lb a.i./A Roundup applications kept plots free of broadleaf weeds until layby. In the nutsedge weed control study, it was found that nutsedge plants treated with a single 1 lb a. i./A application of Roundup were stunted and exhibited leaf chlorosis, but efficacy was marginal with weed control ratings of only 40 to 50 percent. Nutsedge control ratings for an application of norflurazon (i.e., Zorial) alone or combined with Roundup applied at the 1 to 2 true leaf stage of cotton were 63 and 75 percent, respectively. Two sequential applications of Roundup at 1 lb a.i./A, both with or without norflurazon, resulted in about 90 percent nutsedge control. Roundup Ready cotton exhibited good tolerance to two sequential early season 1 lb a.i./A Roundup applications, as made in these studies, with no apparent seed cotton or lint yield reductions.