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.

Field experiments were conducted in 2004 and 2005 at the University of Arizona Maricopa Agricultural Center (1,175ft. elevation) to evaluate the effects of five irrigation termination (IT1, IT2, IT3, IT4, and IT5) dates on yield and fiber micronaire of eleven Upland cotton varieties and one Pima variety. In addition, the economic relationships of IT treatments were also evaluated. The experimental design was a split plot in a randomized complete block design with three replications. The main treatments included the five IT dates and the subunits consisted of 11 Upland varieties and a Pima variety. The first two IT treatments (IT1 and IT2) were imposed with the intention of terminating irrigations very early and pre-maturely at peak bloom. Based upon current UA recommendations for IT to complete a single cycle fruit set, the more optimal date of IT would have included one or two additional irrigations (beyond IT1 and IT2). In this experiment, IT2 was structured to provide an additional (one) irrigation just past peak bloom. For the IT3 plots, the intention was to attempt to time termination in advance of cutout. The 2004 and 2005 IT4 and IT5 were imposed to attempt to complete the primary fruiting cycle development and produce a second cycle fruit set that require irrigations until late August and late September, respectively. In general, lint yield and micronaire results revealed significant differences among the IT treatments and varieties. In a similar fashion to a previous set of IT experiments (2000-2002), lint yield and micronaire values consistently increased with later IT dates. The best combined lint yield and micronaire results were achieved with IT4 date, which received 12 and 18 in. less irrigation water than IT5 in 2004 and 2005, respectively. In 2004 and 2005, the 12 and 18 in. water saved equate to approximately 20% and 30% less water used under the conventional practice, respectively. The average marginal value of water for all eleven Upland varieties in going from IT1 to IT2, IT2 to IT3, IT3 to IT4, and IT4 to IT5 for November 2004 prices and low carrying costs is calculated at $320.07, $150.15, $100.54, and -$28.16 per acre-foot of water. If steeper mike discounts (November 1999), a lower base lint price (45¢/lb.), and higher costs (i.e., more costly insecticide and chemical costs) are imputed to extend the crop, the marginal value of an acre-foot of water for all Upland varieties and replications in going from IT1 to IT2, IT2 to IT3, IT3 to IT4, and IT4 to IT5 is estimated at $164.04, $48.15, $12.97, and -$94.79. Profitability and the value of water for extending the season varies quite markedly between different varieties and termination dates.

Management of phosphorus (P) fertilizer in Arizona cotton production systems has been studied for many years. A series of field experiments have been conducted across Arizona since 1989 with the most recent trial conducted in 2004. These trials represent over 15 site-years of research investigating the response of upland cotton (Gossypium hirsutum L.) to the application of P fertilizers and have been conducted over a wide range of environmental conditions. A summary of these field trials is presented in this paper. All trials were structured in a similar fashion with a control being compared to various rates of applied P fertilizer ranging from 0 to over 120 lbs P₂O₅ per acre. All trials had a similar experimental design with large plots (minimum of 0.16 acres) and treatments arranged in a randomized complete block design with a minimum of three replications in all cases. All applications were made either pre-plant or shortly after stand establishment. A wide range of soil test P levels were evaluated at many locations across the State. Results indicate that the critical level for sodium bicarbonate extractable P is 5 parts per million (ppm) with a 90% probability of a positive lint yield response when soil test levels fall below the critical level. Effective (positive crop response) fertilization rates range from 60-90 lbs of P₂O₅ per acre.

A series of experiments were conducted across three locations in Arizona to evaluate over 40 commercial cotton strains during the 2006 cotton growing season. These trials were conducted in Yuma, AZ (130 ft. above MSL); Maricopa, AZ (1170 ft. above MSL); and Safford, AZ (2900 ft. above MSL). Strains were planted in four row plots extending 38 feet in a randomized complete block design with a minimum of four replications. Each location had three commercial cotton varieties included as control treatments for comparison. Data collected on these trials included a series of plant measurements at three growth stages over the course of the season, yield and fiber quality data. All data were subjected to statistical analysis to test for differences among strains for yield and fiber quality. All three locations produced high yields despite high levels of heat stress in the lower deserts. Statistically significant differences were observed in yield and all fiber quality parameters at each location. Several lines performed considerably better than the commercial control varieties in terms of both yield and fiber quality indicating that continued progress is being made in developing new varieties that perform well in the varied cotton producing regions of Arizona.

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.

Seven foliar fertilizers containing calcium were applied to DPL449BR cotton in the Palo Verde Valley on June 24, 2005, immediately after three consecutive days of level one stress. Plants had been blooming prior to application and had several open blooms per plant at time of application. All treatments increased level of leaf chlorophyll by at least 7.4% when compared with the untreated check as with a Minolta 502 SPAD meter on July 7, with greatest (21.3%) increase noted from Calcium Metalosate®. No statistical differences were noted for this parameter on July 13, and by July 21 highest mean leaf chlorophyll content was noted from untreated cotton. Leaf chlorophyll was lowest in untreated cotton on July 25 however. Shortest stigma lengths beyond anthers on July 13 was noted in treatments with highest amounts of calcium applied per acre, while all treatments had numerically fewer abnormal flowers than the untreated check on July 21. Treatments resulted in slightly taller plants than the untreated check on July 6 and 21, and more nodes on July 6. Most treatments also resulted in more fruiting nodes per plant on July 21 and August 4. Greatest height:node ratios were noted in CalMax® treated cotton on all three sample dates. Highest retention percentages were noted in untreated cotton on July 6 and August 4. All treatments resulted in numerically more fruiting structures/plant than the untreated check on July 21, although only CalMax® treated cotton had significantly more. Most treated cotton had fewer such structures per plant on August 4 than on July 21, however such structures in untreated cotton increased during this time. Calcium Metalosate® was the only treatment that resulted in more seed cotton/acre than the untreated check. Calculated lint yields varied, and reflected the single datum turnout percentage for each treatment derived from commercial ginning of modules. Wide variation in turnout data do not appear to be supported with differences in cotton quality data, as similar economics were noted for all cotton lint on a per pound basis.

Bt cotton is an extremely important tool for integrated pest management in the Southwest. It has been a major factor in the current historic low levels of conventional insecticide use in cotton of this region. This is due to Bt cotton’s unprecedented efficacy against the pink bollworm, Pectinophora gossypiella, and its selectivity in favor of key natural enemies of arthropod pests. Due to the pivotal importance of Bt cotton and widespread concerns about the development of pest resistance to transgenic crops, a multi-agency resistance management program was established to monitor and pro-actively manage resistance development in the pink bollworm. This report constitutes results from the ninth year of this monitoring program. Larvae were obtained from bolls collected in cotton fields located throughout the Southwest, cultured in the laboratory, and offspring tested using diet-incorporation bioassays that discriminate between susceptible and resistant pink bollworm. A total of 11 Arizona and four California collections were successfully reared and tested for susceptibility to Cry1Ac using a discriminating concentration of 10 μg Cry1Ac/ml of diet. Susceptibility to Cry2Ab2 was estimated similarly for 12 strains from Arizona and four from California using diagnostic concentrations of 1.0 and 10 μg Cry2Ab2/ml of diet. Success of pink bollworm eradication in suppressing pink bollworm populations in New Mexico and Texas precluded successful collection of samples in those states. No survivors of 10 μg Cry1Ac/ml were detected in any bioassays of 2005 strains (n=5358). The grand mean frequency of PBW survival of 10 μg Cry1Ac/ml in 2005 was 0.000%. A susceptible culture, APHIS-S, used each year as an internal control, yielded 99.3% corrected mortality in tests of 10μg/ml Cry1Ac (n=490). All twelve pink bollworm strains collected in 2005 were highly susceptible to Cry2Ab2, based on contrasts with baseline data collected from 2001-2003. There were no survivors of bioassays of either 1.0 μg Cry2Ab2/ml (n=1,000) or 10 μg Cry2Ab2/ml (n=3425). The susceptible APHIS-S culture had 82.5% corrected mortality in tests of 10 μg/ml Cry2Ab2 (n=200) and 100% mortality in tests of 10 μg/ml Cry2Ab2 (n=120). Field evaluations of efficacy of Bt cotton were conducted by the Arizona Cotton Research and Protection Council in adjacent pairs of Bt and non-Bt fields at 44 Arizona locations. Statewide, large pink bollworm larvae were found in an average of 15% of non-Bt bolls sampled from borders of refuge fields. This was on the low end of the range of infestation levels observed in refuges during the past decade. Bolls from adjacent Bt cotton (Bollgard™) fields yielded an average of 0.28% infested bolls. This value was down slightly from the previous year. Over 70% of the pink bollworm recovered from collections in Bt fields were from bolls that did not express Bt toxin. We conclude that there was no indication of problems with pink bollworm resistance to Cry1Ac or Cry2Ab2 at the locations sampled in 2005. Moreover, Bt cotton continued to exhibit exceptional field performance in Arizona.

We report biotype identifications and susceptibility to insecticides of whiteflies (Bemisia tabaci) collected from cotton, vegetables, melons and ornamental plans during the 2005 season. No major problems with field performance of insecticides against whiteflies were confirmed in 2005 in Arizona. Whitefly resistance to pyriproxyfen did not increase, relative to levels recorded in 2004. However, we detected pyriproxyfen resistance in all Arizona whitefly samples tested. A single sample collected from cotton in Holtville, CA, had no detectable resistance to pyriproxyfen. Samples from cotton in Buckeye, Coolidge, Scottsdale, and stanfield, Arizon,a had the highest levels of resistance, with > 31-45% of eggs surviving diagnostic concentration bioassays of 0.1 ug/ml pyriproxyfen. Whitefly susceptibility to buprofezin (Applaud®/Courier®) has not changed significantly since 1997. Resistance to synergized pyrethroids (e.g., Danitol® + Orthene®) has decreased strikingly on a statewide basis since 1995, though unacceptably high frequencies of resistant whiteflies were detected in some 2005 collections from all commodities sampled. Whiteflies collected from Arizona cotton, melons, and vegetables continued to be highly susceptible to imidacloprid (Admire®/Provado®). One whitefly collection from poinsettias in Phoenix (05-39) was substantially less susceptibile to imidacloprid, and the related neonicotinoid insecticides, acetamiprid, and thiamethoxam. Regression analysis yielded a significant correlation between acetamiprid and thiamethoxam. Whiteflies from cotton that were least susceptibile to acetamiprid were also significantly less susceptible to thiamethoxam (Actara®/Centric®/Platinum®). The most worrisome of our 2005 findings was that 6 out of 13 samples of whitefly-infested poinsettias collected from retail stores in metropolitan Tucson and Phoenix consisted of only the Q biotype of Bemisia tabaci. The plants were infested with very low whitefly numbers and thus we were unable to establish them in laboratory cultures and evaluate their resistance status. The Q biotype is native to Spain and was first detected in the US by our group in 2004 on a sample taken from poinsettias. Our concern is that the Q biotype strain we detected in 2004 was highly resistant to a broad range of insecticides used to manage whiteflies in Arizona. None of the 26 field collections evaluated in 2005 was the Q biotype.

In the Western U.S., Lygus spp. (Hemiptera: Miridae) can cause major losses to cotton, vegetables, seed crops, and a variety of other crops. However, the economic impact of this pest remains largely undocumented in most crops. Two major data sources were used to quantify the economic impact of Lygus in lowdesert upland cotton production in Arizona: a statewide Pesticide Use Reporting (“1080”) database and an annual “Cotton Insect Losses” (CIL) survey of cotton Pest Control Advisors (PCAs). Both data sources include information on the target pest for insecticide applications, making it possible to single out Lygus control efforts. PUR data, based on information submitted by applicators to the Arizona Department of Agriculture, provides quantitative information on a high proportion of Lygus applications in cotton, but is incomplete, since not all types of applications require reporting. These data are complemented by information from the CIL survey to provide a more complete picture, based on direct responses from PCAs about their pest management practices. While the 1080 database is very useful in documenting a high proportion of Lygus insecticide use in cotton, by definition, these data on their own cannot provide good estimates of statewide behaviors with respect to Lygus management. In contrast, this is exactly what the Cotton Insect Losses survey is designed to do. As indicated by 1080 data and CIL data from 2001 to 2005, Lygus is the most important pest in Arizona cotton most years, based on application*acres of all foliar insecticides. Other key pests by this measure are sweetpotato whitefly, Bemisia tabaci Genn., and to a lesser extent pink bollworm, Pectinophora gossypiella (Saunders). Whitefly is the most important Lygus co-target, when applications are aimed at controlling more than one pest. The most commonly used foliar materials against Lygus in Arizona cotton are acephate, endosulfan and oxamyl, and they are typically used at about 90% of maximum label rates. About 80% of Lygus applications occur between mid-July and late-August. Average spray intensity (based on average sprays per acre) was calculated independently using the CIL and 1080 data sets and compared. For every year except for 2004, the CIL data estimates a somewhat higher insecticide use against Lygus . Several reasons for this discrepancy were identified, including less than 100% pesticide use reporting on 1080s; differences in the insecticides included in the estimates (top three active ingredients only for 1080 estimate, all insecticides for CIL estimate); and differences between how the two datasets apportion a single spray event among multiple pest targets. The intensity of Lygus management varies by county, based on 1080 data and county-level information on cotton acreages. Pinal county, which has the most cotton acres, shows the highest sprays / acre of the top three active ingredients to control Lygus . Analysis of 2005 1080 data at the section level indicates a relationship between the proportion of sections where cotton is grown in a Township - Range and spray intensity for Lygus control. Growers in Township - Ranges with a low proportion of cotton sections (10–15%) tend to make more sprays per field to control Lygus . However, Township – Ranges with the lowest and highest proportions of cotton sections (<10% and >90%) tend to show trends of lower spray requirements for Lygus control. These data suggest the possibility that landscape factors can influence Lygus populations at the local level, although more research in this area is needed. Lygus is perhaps the most significant economic pest of Arizona cotton. Cotton Insect Losses survey data indicate that a high proportion of cotton insect pest management efforts are directed toward Lygus control. Up to 40% of foliar insecticide sprays target Lygus , for about one third of the foliar insecticide budget for growers most years. Despite these control efforts and associated costs, Lygus are consistently listed in the CIL by survey respondents as the most damaging insect pest of cotton, accounting for more than 50% of insect-related yield loss most years. These two different and complementary data sets provide important baseline information on the current status and economic impact of Lygus in Arizona cotton, which will be useful for measuring changes in Lygus impact and control practices over time. A number of factors could potentially impact these practices in the future including (1) the introduction of new selective chemistry for Lygus control; (2) the introduction of transgenic control options for Lygus ; and (3) landscape-level changes that can have area-wide impact on Lygus management in cotton and other crops. These data underscore the need for continued research to develop effective, selective tools for improved Lygus management in cotton, and to integrate these into effective IPM programs. Data documenting a pest’s economic impact provides a rationale for funding to support critical IPM research and education. There is a need to similarly document the economics of Lygus management in other crops including vegetables, seed crops, and alfalfa, and the impact of landscape-level factors on Lygus management in a variety of crops.

Field experiments have been conducted for the past 19 seasons at three Arizona locations on University of Arizona Agricultural Centers (Maricopa, MAC; Marana, MAR; and Safford, SAC. aimed at investigating nitrogen (N) fertilizer management in irrigated cotton (Gossypium spp.) production. The MAC and SAC experiments have been conducted each season since 1989 and the Marana site was initiated in 1994. The original purposes of the experiments were to test N fertilization strategies and to validate and refine N fertilization recommendations for Upland (G. hirsutum L.) and American Pima (G. barbadense L.) cotton. The experiments have 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 ranged from a conservative to a more aggressive approach of N management. The integrity of the experimental sites at each location was maintained in each consecutive season. 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 consistently benefit yields at any location. Generally, the more conservative, feedback approach to N management provided optimum yields at all locations. In 2001, a transition project evaluating the residual N effects associated with each treatment regime was initiated and no fertilizer N was applied. From 2001 to 2005 the residual N studies were conducted at two of these locations (MAC and MAR). In 2006, the residual N study was conducted only at MAC (the University of Arizona ceased operations at MAR at the end of the 2005 season). Therefore, all N taken-up by the crop was assumed to be derived from residual soil N. However irrigation water analysis showed that NO₃⁻-N concentration levels added to the crop ranged from about 5 to 15 ppm. In 2001- 2005 there were no significant differences among the original fertilizer N regimes in terms of residual soil NO₃⁻-N concentrations, crop growth, development, lint yield, or fiber properties. In 2006 however, significant differences in lint yield among N fertilization regimes for the Maricopa location were found. This suggests a possible pattern associated with the residual fertilizer N effects in relation to the original treatments at the Maricopa site.