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.

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.

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.

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.

The upland cotton variety trial has been conducted in Arizona every year for the past 6 years to evaluate several varieties of upland cotton. Varieties planted at each location are planted side-by-side to evaluate performance and yield under the same growing conditions. Eleven locations were planted in Arizona in 2005. These locations include two locations in the Yuma Region (Yuma County), two locations in the Western Region (La Paz and Mohave Counties), four locations in the Central Region (Maricopa and Pinal Counties), one location in the Southern Region (Pima County), and two locations in the Eastern Region (Graham and Cochise Counties). Each site had between seven and eleven varieties evaluated for yield and quality of lint.

A series of experiments were conducted across two locations in Arizona to evaluate 32 advanced and preliminary strains from the Arizona Cotton Growers Breeding Program. These trials were conducted in Yuma, AZ (130 ft. above MSL) and Maricopa, AZ (1170 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 and yield and fiber quality data. All data were subjected to statistical analysis to test for differences among strains for yield and fiber quality. Both 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. Yield was down in Yuma as compared to previous years ranging from 1100 to 1800 lbs lint/acre. Yield at Maricopa was up significantly from last year with yields ranging from 1400 to 2100 lbs lint/acre. Significant increases in staple length was observed with several ACGA lines over control varieties at both locations with one line in particular producing a staple length of nearly 40 (ACGA 107). Several ACGA lines possess excellent fiber quality and performed well in terms of yield at both locations.