A series of experiments were conducted in 2003 in the Upper Gila River Valley in Safford, AZ to evaluate several different formulations of the plant growth regulator (PGR) Pix manufactured by BASF. Two experiments were conducted at the Safford Agricultural Center (SAC) while the third was conducted on a grower-cooperator field in the same valley. Experiments conducted at SAC involved evaluating the four formulations of Pix (Pix, Pix Plus, Pix Ultra, and Pentia) in a standard (STD) treatment regime and a low rate multiple (LRM) regime. The untreated control plots in both the LRM and STD experiments produced higher yields than any of the other PGR formulations. Comparing only the PGR formulation treatments the Pentia treatment produced the highest yield in both the STD and LRM experiments. No significant differences were observed in fiber quality for either the LRM or STD experiment. The third experiment conducted on a growercooperator field was a Pentia demonstration experiment. Three treatments including a control, a standard, single Pentia application, and an aggressive split application of Pentia were employed. The highest yield was produced in the most aggressive Pentia treatment. Results from this set of experiments demonstrate the importance of incorporating information from plant monitoring techniques when making decisions about PGR applications.

An experiment to investigate the effects of several plant growth enhancement products (AuxiGro7 WP, FirstChoice7 Bollster, CalMax, FoliGro7 BollSet) on DPL 451BR was conducted in the Palo Verde Valley. The cotton field chosen for this project was planted in April 2003, and flowering and boll/lint production was highly affected by summer heat, therefore product effectiveness was tested under the extreme high temperatures conditions that existed in 2003. Products were applied July 11 (shortly after first bloom), August 1st and/or August 15. Three rates (1, 2, 4 oz./acre) of AuxiGro7 WP were applied at each date, although just a single rate of other products was evaluated. Data collected included plant mapping following the first two application dates as well as lint yield and quality at harvest on October 20-23. Data indicated rate effects for treatments containing AuxiGro7 WP as noted in response to applications on August 1 (retention rates) and August 15 (cotton quality factors). These responses were signficantly different than the untreated check, and were often signficantly different than the Bollster fertilizer treatment itself as though Bollster was also included with AuxiGro7 WP treatments. Although yields for any treatment and the untreated check were not significantly different, previously noted differences for retention for the AuxiGro7 WP treatments may not have been realized due to the high temperatures and extended periods of not only Level 1 but Level 2 stress during the course of the experiment. Cotton values per acre were highest ($609.85/acre) in the 4 oz/acre of AuxiGro7 applied on August 15, due to highest valued lint as a result of micronaire of 5.2 combined with increased fiber strength and fiber length. Application of CalMax resulted in a significant increase in fiber strength following two applications of 4 oz./acre of AuxiGro7 + Bollster, but CalMax following two applications of Bollster did not affect fiber strength when compared with each of the two application treatments. A third application of FoliGro7 BollSet was detrimental for cotton yields and strength compared with only two applications of this product, although both treatment regimens resulted in shorter fibers that were not quite as strong as the untreated check.

A single field study was conducted during the 2004 cotton growing season at the University of Arizona Safford Agricultural Center to evaluate the effect of two plant growth regulators (PGRs) manufactured by LT Biosyn Inc. on the growth, development, yield, and fiber quality of cotton grown in the southeastern region of the state. This test was designed as a follow up study to work that was performed in 2003 on a grower cooperator site that demonstrated positive lint yield responses to the use of one of the PGRs used in this project. This was an eight treatment test involving the application of two PGRs, HappyGroTM (HG) and MegaGroTM (MG). The two formulations are intended to have different effects on plant growth and development. The HG formulation is a kinetin based product designed to enhance cell division and differentiation. The MG formulation is designed to enhance root growth early in the season. Several treatment combinations were designed to investigate varying scenarios of application of these two products alone and in conjunction with each other. The test included a control and each treatment was replicated four times in a randomized complete block design. Plant measurements were collected throughout the season to look for differences in plant growth and development. Lint yield was estimated by harvesting the entire plot and weighing the seedcotton with a weigh wagon equipped with load cells. Sub samples were collected for fiber quality and percent lint determinations. Plant measurements revealed extremely high fruit retention levels throughout the entire season with end of season levels near 75%. This high fruit retention resulted in very low vigor. Under these conditions, while lint yield was extremely high for this region (1300-1600 lbs. lint per acre), no statistical differences were observed among treatments. Fiber quality measurements also revealed no significant differences.

Two separate defoliation experiments were conducted during the 2004 growing season in an effort to evaluate the effectiveness of commercially available harvest preparation materials alone at full label rates and to also evaluate these materials at reduced rates with the addition of various synergistic chemicals designed to enhance the effectiveness of commercially available harvest prep materials. The studies were conducted at the University of Arizona Safford Agricultural Center on both Upland (cultivar DP555BR) and Pima (cultivar DP340) cotton. Plots were planted on 20 April and 27 April for the Upland and Pima, respectively. Plots were arranged in a randomized complete block design with four replications and treatments included Ginstar at recommended rates and Ginstar at reduced rates with the addition of three chemical enhancement materials (A, B, and C). Sodium chlorate was also included at a full rate and at reduced rates with the three enhancement materials. A control, not receiving any harvest prep material was also included for a total of eleven treatments. Treatments were imposed on 15 October and evaluations were made on 27 October and 4 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. Results indicated that the most effective treatment for both Upland and Pima trials was Ginstar at the full rate. Reduced rates of Ginstar in combination with the enhancement chemicals of B and C also provided good defoliation results. The chemicals that were designed to enhance the efficacy of the commercial harvest prep materials appeared to have an antagonistic affect with the sodium chlorate. Defoliation effectiveness decreased with the addition of chemicals A, B, and C to sodium chlorate. No statistical differences were detected among lint yield or any of the fiber quality parameters in any of the treatments of both the Upland and Pima trials.

A single field study was conducted at the University of Arizona Safford Agricultural Center during the 2004 season to evaluate the utilization of a feedback technique that is based upon plant growth and development to schedule applications of the new plant growth regulator (PGR) from BASF, Pentia. A simple three treatment study was constructed consisting of a control treatment (no Pentia application), a scheduled treatment (application of 16 oz/acre at first bloom regardless of plant growth), and a feedback treatment (applications based upon plant growth and development). Application decisions on the feedback treatment were made using height to node ratios (HNR) as a measure of plant vigor. Treatment applications were made on the scheduled regime on 14 July with a one time 16 oz/acre application. The feedback regime received an application (16 oz/acre) of Pentia five days later on 19 July. An additional application (16 oz/acre) was made on the feedback treatment on 3 August due to continued high HNR levels. Significant differences in plant vigor were observed post application among the three treatments as measured by end of season HNR ratios. Yield results indicated positive lint yield response to Pentia application with both the scheduled and feedback treatment producing statistically higher yields than the control. Differences between the feedback and scheduled treatments were not statistically different however a slight yield increase was observed in the scheduled treatment. The second Pentia application made to the feedback treatment was not necessary. End of season HNR measurements indicate that the additional 16 oz/acre application suppressed growth to below the average baseline for HNR. These results indicate that potential positive response to PGR applications, specifically Pentia, under conditions of high vigor.

A single field trial was conducted during the 2004 season to evaluate three different mepiquat formulations used to control vegetative plant growth. This project involved the evaluation of mepiquat formulations of Mepex Ginout (DuPont), Pix Ultra and Pentia (BASF). These three treatments, along with a control, were arranged in a randomized complete block design with four replications. Plots were 20, 36” wide rows and extended for a full one half mile irrigation run. Applications of all treatments were made on 22 July 2004 at a rate of 16 oz/acre for each formulation. Lint yields were determined at the end of the season by harvesting the center eight rows of each plot. The harvested seed cotton was weighed using a weigh wagon equipped with load cells. Sub samples were collected from each plot for fiber quality and lint percent determinations. No significant differences were observed among treatments with respect to any of the fiber quality parameters measured. The Mepex Ginout treatment produced the highest lint yield and also the highest percent lint. The control was not significantly different from the other two formulation treatments. Lint percent values had a major impact on lint yield. The control had the lowest seed cotton yield but because of the higher percent lint values, lint yield for the control was ultimately higher than both the Pentia and Pix Ultra treatments. This study demonstrates the positive effect of the PGR applications and also the effect that percent lint can have on final lint yield.

A single defoliation experiment was conducted during the 2004 growing season in an effort to evaluate the effectiveness of commercially available harvest preparation materials in the higher elevation areas of southeastern Arizona. Many growers will not employ a defoliation regime but will let the crop naturally senesce with the cooler temperatures and frost. This evaluation compared a standard treatment of Ginstar with some additional tank mix ethephon based products from DuPont and BASF. These treatments were compared to the common Na chlorate treatment employed by many growers in this region of the state. Treatments included a base rate of 8 oz/acre Ginstar with three different rates of both CottonQuick and Prep. Treatments were applied on 15 October in a randomized complete block design with four replications. Data collected included observations of percent defoliation, percent regrowth control, and percent open boll on two separate dates after treatment (27 October and 4 November). Yield data was also collected at the end of the season by harvesting the center two rows of each plot. Sub samples were collected for fiber quality analysis. Results showed significant differences among treatments with respect to defoliation parameters measured. Treatments including Ginstar and higher rates of both CottonQuick and Prep performed well. The treatment consisting of Na chlorate alone was also effective. The Ginstar + CottonQuick treatment did appear to have a slight advantage in final percent open boll counts. No significant differences among treatments were detected with respect to yield and fiber quality. However, lint yield for the control treatment was lower than the other defoliation treatments. This would indicate that some type of defoliation regime does provide benefit in terms of increased yield.

A single trial was conducted during the 2005 cotton growing season at The University of Arizona Safford Agricultural Center to evaluate the effects of the selective herbicide Envoke in combination and alone with the plant growth regulator (Pix). Combining applications of chemical inputs in a crop production system has the potential to help reduce costs by eliminating a trip across the field with equipment. The effects of these applications on growth, development, yield, and fiber quality was investigated. The trial was arranged with seven treatments including 1) control, 2) broadcast Envoke, 3) post-direct Envoke, 4) broadcast Pix, 5) broadcast Envoke + Pix, 6) post-direct Envoke followed by broadcast Pix, and 7) broadcast Pix followed by post-direct Envoke. These treatments were imposed in both normal and high soil moisture regimes. Plots were arranged in a randomized complete block design with four replications in two separate studies (normal and high soil moisture). Plots were monitored for effects on plant growth and development throughout the season by collecting a series of plant measurements from each treatment. Effects on final lint yield and fiber quality was determined by harvesting the center two rows of each four-row plot and weighing the resultant seed cotton. A sub-sample was collected for lint turnout and fiber quality analysis. Results indicated very little differences in plant growth and development among any of the treatments in both the normal and high moisture regimes. Significant differences were observed among lint yield and fiber quality parameters. Analysis of variance indicated significant effects due to treatment in lint yield, fiber length, strength, and uniformity. Significant differences were also observed due to soil moisture with respect to micronaire and fiber strength. Significant interaction between treatment and moisture regime was observed in micronaire, fiber length, strength, and uniformity. Results indicate that even though plant growth and development did not appear to be significantly impacted by the application of Pix + Envoke, lint yield was impacted. In both the normal and high soil moisture regimes the treatment receiving the combined application of Pix and Envoke produced the lowest yield.

Two rates of the ethylene blocker ReTain® were evaluated on four varieties of cotton in the Palo Verde Valley during the summer of 2005. Data indicated that responses to ReTain® varied greatly by variety. Application of ReTain® to DPL 555BR resulted in significant increases in numbers of fruiting structures per plant, however, these increases were not realized at harvest, as ReTain® treatments resulted in numerically reduced yields for this variety. Bolls per plant at harvest were not signficantly different for DPL 449BR, DPL 5415R or STV 5599BR. Both rates of ReTain® significantly increased uniformity of DPL 555BR cotton lint, but the lower rate of ReTain® evaluated usually resulted in slightly higher cotton lint quality for most components measured than did the higher rate. Quality and yield data were not collected for DPL 449BR, DPL 5415R or STV 5599BR.

Eight varieties were evaluated under field conditions for resultant plant populations after field infection with Rhizoctonia solani. Highest plant populations were noted in Delta and PineLand 454BR, followed by three other Delta and PineLand (DPL) varieties. Stoneville and Phytogen cotton varieties had reduced plant stands compared to DPL varieties at approximately 30 days after planting. DPL 454BR, which had the highest plant population, also had earlier growth and establishment than other varieties which is thought to have helped plant survival. Although all seed was treated with multiple fungicides, seed of DPL varieties was treated with several fungicide active ingredients (thiram, tridimenol) not present on seed from other varieties. Comparative increased stand on DPL varieties may be in part due to plant genetics as well as fungicide. Stand loss was noted in all varieties however. Data indicate that in-furrow application of fungicides or applications to small cotton plants may be necessary for heavier soils under cool and moist early season growing conditions in the low desert.