A field experiment compared several rates of mepiquat chloride and Goëmar® BM86 on Upland cotton in the Palo Verde Valley during 2005 for their effects on cotton growth and yields. Leaf chlorophyll levels were significantly increased in DPL 449BR by usage of mepiquat chloride on initial samples dates after applications, and these treatments also effected cotton heights. Retention percentages and numbers of fruiting structures per plant were initially increased by treatments which contained Goëmar® BM86, although late in the season significant differences existed between Goëmar® BM86 treatments as a result of interaction with mepiquat chloride. All treatments resulted in a slight (0.01 inch) increase in fiber length as well as staple, resulting in increased lint value. The combination treatment of Goëmar® BM86 plus 12 oz./acre of mepiquat chloride had highest cotton value ($1,035/ acre), and was worth $178/acre more than the untreated check.

Three plant growth enhancement chemistries (AuxiGro®, ChaperoneTM, HappyGroTM) were evaluated on DPL 449BR cotton during the summer of 2005, Application were made during mid-July to late planted cotton to evaluate and compare effects of these products on cotton growing under severe heat and growth stress to determine if such chemistries could overcome this stress. Two foliar fertilizers were included with two formulations of AuxiGro® to determine if differences associated with these treatments existed. Usage of HappyGroTM = PhotoGroTM resulted in the most fruiting structures/plant while treatments that included ChaperoneTM resulted in reduced numbers of structures when compared with the untreated check on August 24. Highest yields among products tested were noted for the formulations of AuxiGro® 518 which were slightly higher than the untreated check. Quality was improved in comparative formulations of AuxiGro® by inclusion of CalMax® + First Choice® Foliar Pride when compared with First Choice® Bollster.

Three plant growth enhancement treatments were applied to April-planted DPL 555BR cotton on the morning of July 2, 2005. Plant parameter data were obtained during July, and yield and quality data were obtained at harvest in December. Usage of ChaperoneTM resulted in decreased potassium and phosphorus levels in petioles, as well as increased amounts of leaf chlorophyll. Treatments initially resulted in less fruiting structure/plant but had more than the untreated cotton at 26 days post treatment, with highest numbers per plant noted from the HappyGroTM + PhotoGro treatment. Each treatment resulted in less seed cotton and lint per acre than the untreated cotton. Less spotting associated with treated cotton increased the lint strength and increased trash levels. The AuxiGro® WP + CalMax® + Foliar Pride treatment resulted in the highest fiber strength per pound and lint value.

Chaperone™ was applied in mid-July to three different cotton varieties (DPL 449BR, DPL 555BR, STV 5599BR) being grown in the same field. Varieties differed in their responses, with application of Chaperone™ resulting in fewer fruiting structures per plant than untreated DPL 449BR or STV 5599BR, but more such structures in DPL 555BR. Seed cotton yields were increased in DPL 555BR by almost 300 lbs./acre by application of Chaperone™, but were only about 20 lbs./acre greater in the other two varieties. A higher percentage of lint in seed cotton was associated with Chaperone™ application in both DPL 449BR and STV 5599BR, but a lower percentage in DPL 555BR. Calculated lint yields increased in both DPL 449BR and STV 5599BR, but yields were almost identical for treated/untreated DPL 555BR in this experiment. Application of Chaperone™ resulted in a slight increase in fiber uniformity in all three varieties.

This study was conducted in 2005 at the University of Arizona Maricopa Agricultural Center. The objective was to compare the performance of various PPO inhibitors [Aim (carfentrazone-ethyl), ET (pyraflufen-ethyl), Blizzard (fluthiacet-methyl) and Resource(flumiclorac)] as stand-alone defoliation treatments either as a single or sequential application, or tank mixed with Ginstar or CottonQuik. Plots were arranged in a randomized, complete block design with four replicates. Each plot was composed of four, 40 inch rows that measured 25 feet long. Delta and Pine variety DP 449BR was planted on 12 April 2005. Treatments included: Ginstar @ 6 oz/A, Ginstar @ 8 oz/A, Aim @ 1 oz/A, ET @ 1.5 oz/A, Resource @ 8 oz/A and Blizzard @ 0.5 oz/A, Aim followed by Aim, ET followed by ET, Blizzard followed by Blizzard, Resource followed by Resource, Ginstar @ 6 oz/A plus Aim, Ginstar plus ET, Ginstar plus Resource, Ginstar plus Blizzard, CottonQuik at 32 oz/A plus Aim, CottonQuik plus ET, CottonQuik plus Resource, and CottonQuik plus Blizzard. All treatments receiving a PPO inhibitor also contained a Crop Oil Concentrate at 1% v/v. None of the PPO inhibitors applied as a single application performed as well as Ginstar at either the 6 oz/A or 8 oz/A rates. At 14 days after treatment (DAT), both Aim and Blizzard achieved 74% defoliation, Resource 69% and ET 60%. For sequential applications at 14 DAT, Aim at 1.5 oz/A followed eight days later by a second application of Aim performed as well as the standalone applications of Ginstar at 6 oz/A and 8 oz/A. Two applications of Blizzard at 0.5 oz/A eight days apart defoliated as well as Ginstar at 6 oz/A. Tank mixing any of the four PPO inhibitors with Ginstar did not improve defoliation over Ginstar alone, at either rate nor did defoliation rates decrease as a result of the mixes. A mixture of Aim + CottonQuik (75%) defoliated as well as a standalone treatment of Ginstar (82%).

This study evaluated the effectiveness of defoliating at various heat unit accumulations: 630HU, 730 HU, 830 HU, 930 HU, 1030 HU, 1130 HU and 1330 HU and impact on lint yield and fiber quality. American Upland cotton variety DP 449 BR was planted on 12 April 2005 at the University of Arizona Maricopa Agriculture Center in Maricopa, Arizona. The experimental design was a split plot with four replications of each of seven defoliation timings. Final irrigation occurred on 05 August 2005. When heat unit accumulation reached 630 HU (on 20 August 2005), 730 HU (on 01 September 2005), 830 HU (on 04 September 2005), 930 HU (on 08 September 2005), 1030 HU (on 12 September 2005), 1130 HU (on 19 September 2005) and 1330 HU (on 27 September 2005) using the 86/55 F model chemical defoliants were applied. A mixture of Def (tribufos) at 24 oz/A, Dropp (thidiazuron) at 0.2 lb/A and Prep (ethephon) at 24 oz/A was applied using a high clearance research sprayer. The earliest treatments (630 and 730 HU accumulated) had significantly fewer open bolls at defoliation than those that received later treatments. At harvest, this trend disappears: the latest application (at 1330 HU) had significantly fewer open bolls than any other timing. Seven days after defoliant application (7 DAT), highest levels of defoliation were observed in the following treatments in descending order: 830 HU, 630 HU, 1130 HU, 930 HU and 730 HU followed by 1030 HU and 1330 HU. At harvest, there were no significant differences among mean defoliation percentages with the exception of the 1330 HU timing, which was significantly less defoliated than any of the other timings. Highest lint yield and gin turnout were observed in the earliest defoliation timings, lowest in the later timings. No significant differences in micronaire, length or uniformity were observed between defoliation timings. Differences did occur in fiber strength which was highest in earlier timings and lowest in the last timing, but all were above the discount level.

A defoliation experiment was conducted during the 2005 growing season in an effort to evaluate effectiveness of the Ginstar™ defoliant alone and in combination with Cotton Quick™. This study was conducted at the University of Arizona Safford Agricultural Center on Upland (cultivar DP655BR). Plots were planted on 22 April. Treatments were arranged in a randomized complete block design with four replications and treatments that included Ginstar™ at 6 and 8 oz./acre rates and Ginstar™ at the 6 and 8 oz./acre rates in combination with various rates of Cotton Quick™ (1.5, 2, 3, and 4 pts/acre). A control, not receiving any harvest prep material was also included for a total of eleven treatments. Treatments were imposed on 3 October and evaluations were made on 14 October and 26 October. Estimations on percent leaf drop, regrowth control, and open boll were made. Lint yield was estimated by harvesting the center two rows of each plot and sub-samples were collected for fiber quality analysis. Plots were harvested on 26 October in an attempt to evaluate the boll opening effectiveness of the Cotton Quick™ material. Results indicated increased leaf drop in lower Ginstar™ rates with the addition of Cotton Quick™. Measurements of open boll percentages did not indicate any increase with the addition of Cotton Quick™ however, lint yield and fiber quality parameters would demonstrate otherwise. Lint yield slightly increased in all treatments receiving Cotton Quick™ while fiber micronaire decreased in Cotton Quick™ treatments. This would indicate a blending of less mature bolls opened with the addition of Cotton Quick™ with those already opened. Percent lint also increased in all treatments receiving Cotton Quick™.

A single experiment was conducted in 2005 at the University of Arizona Safford Agricultural Center in an effort to continue to evaluate several different formulations of the plant growth regulator (PGR) mepiquat chloride. Plots were established with the cultivar Deltapine DP 655BR on 19 April 2005. Four treatments were imposed on 18 July 2005 of 16 oz./acre applications of Mepex, Pix Ultra, and Pentia, plus a control plot. Plots were four 36” rows wide and extended the length of the irrigation run of 220 feet. Plots were arranged in a randomized complete block design with four replications. Plots were monitored with respect to plant growth and development through collecting plant measurement data over the course of the season. Yield results were obtained by harvesting the center two rows of each plot and weighing the resultant seedcotton. Fiber quality was determined from a sub-sample collected from each plot at harvest. Plant growth and development trends indicated strong fruit retention levels all season with strong early season vigor. Each of the PGR applications had significant impact on plant height effectively reducing internode elongation. Lint yield results indicated increased yields for all PGR applications over the control with Pentia producing a statistically significant higher yield. Fiber quality was also impacted by PGR application. All PGR treatments had trends toward higher staple length, fiber strength, and fiber uniformity. These results are consistent with previous results indicating that PGR applications have the potential to increase yields under situations were high vigor is present.

Studies were conducted in 2002, 2004, and 2005 at the University of Arizona Maricopa Agricultural Center located near Maricopa, Arizona. Objectives of the study were to evaluate the efficacy of contact herbicides for defoliation as a second application and evaluate any potential improvement in lint return (gin turnout), fiber quality and overall lint value. In 2002, Delta and Pine cultivar 458 BR was planted on 17 April. In 2004 and 2005 Delta and Pine cultivar 449 BR was planted on 13 May and 12 April respectively. In all years, plots were 13.33 ft wide and 25 ft long and treatments were arranged in a randomized complete block with four replications. Irrigation was terminated at cutout (NAWF=5) and defoliation treatments were initiated 22 days later. All plots received an initial defoliation treatment of thidiazuron plus diuron (Ginstar) at 8 oz/A. In 2002 and 2004, follow-up applications occurred seven days after initial defoliation, and included the following treatments: paraquat (Gramoxone Max) at 10.7 oz/A plus nonionic surfactant at 0.25%v/v, flumiclorac (Resource) at 8 oz/A plus crop oil concentrate (COC) at 1% v/v, pyraflufen (ET) at 1.5 oz/A plus COC at 1% v/v or carfentrazone (Aim) at 1.0 oz/A plus COC at 1% v/v. In 2005, follow-up application occurred eight days after initial defoliation and included the same treatments as 2002 and 2004 with the addition of fluthiacetmethyl (Blizzard) at 0.5 oz/A plus COC at 1% v/v and an adjustment of the Gramoxone Max rate to 20 oz/A. For comparison purposes, in all years, one treatment did not receive a follow-up application. In 2002 and 2004, percent defoliation was significantly higher in treatments that received an application of Ginstar followed by Aim, Resource, ET or Gramoxone Max compared with a single application of Ginstar. However, follow-up treatment with Gramoxone Max at 10.7 oz/A provided significantly less defoliation than Aim or ET treatments. In 2005, defoliation was significantly increased by follow-up application with all of the contact herbicides evaluated, No significant differences were observed in gin turnout, lint yield or loan value in the years these variables were evaluated.

A defoliation experiment was conducted during the 2006 growing season in an effort to evaluate the effectiveness of Ginstar® and FreeFall® defoliant alone and in combination with CottonQuik®. This study was conducted at the University of Arizona Safford Agricultural Center on Upland (cultivar DP655BR). Plots were planted on 20 April. Treatments were arranged in a randomized complete block design with four replications and treatments included Ginstar® at 6 and 8 oz./acre rates and Ginstar® at the 6 and 8 oz./acre rates in combination with various rates of CottonQuik® (1.5, 2, 3, and 4 pts/acre). We also evaluated a new product from DuPont, FreeFall® SC at different rates (3.2, 4.8, 6.4 oz./acre) in combination with CottonQuik® (2 pts./acre). The standard defoliation protocol among growers in southeastern Arizona is sodium chlorate plus Gramoxone®, so this treatment combination was also included. A control, not receiving any harvest prep material was also included for a total of fifteen treatments. Treatments were imposed on 13 October and evaluations were made on 20 October and 1 November. Estimations on percent leaf drop, regrowth control, and open boll were made. Lint yield was estimated by harvesting the center two rows of each plot and sub-samples were collected for fiber quality analysis. Plots were harvested on 2 November directly after the second evaluation date in an attempt to evaluate the boll opening effectiveness of the CottonQuik® material. Results indicated higher effectiveness of leaf drop or defoliation in the plots that included CottonQuik® as opposed to Ginstar® alone. The treatments performed much better that the standard sodium chlorate treatment. Percent leaf drop also increased at the higher rates of FreeFall® (4.8, 6.4 oz./acre). The percentage of open boll was also improved with the addition of CottonQuik® to the all of the treatments. However, very little significant differences were observed in lint yield and fiber quality. A trend of increased yield with the addition of CottonQuik® was observed when compared to Ginstar® alone or the standard sodium chlorate treatment. All aspects of harvest preparation including percent defoliation and boll opening appear to be significantly enhanced with the use of CottonQuik® when compared to standard Ginstar® rates alone.