• Biotype Designations and Insecticide Susceptibility of Southwestern Bemisia tabaci

      Dennehy, Timothy J.; DeGain, Benjamin A.; Harpold, Virginia S.; Nichols, Robert J.; Tronstad, Russell; University of Arizona. Tucson, AZ; Cotton Incorporated, Cary, NC (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      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.
    • Susceptibility of Southwestern Pink Bollworm to Bt toxins Cry1Ac and Cry2Ab2 in 2005

      Dennehy, Timothy J.; Unnithan, Gopalan C.; Harpold, Virginia; Carrière, Yves; Tabashnik, Bruce; Antilla, Larry; Whitlow, Mike; Tronstad, Russell; Department of Entomology, The University of Arizona, Tucson, AZ; Arizona Cotton Research & Protection Council, Phoenix, Arizona (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      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.
    • Effects of Calcium Containing Foliar Fertilizers on DPL449BR Cotton in the Palo Verde Valley, 2005

      Rethwisch, Michael D.; Ramos, D. Michael; Luna, Manuel; Wellman, Jessica; Tronstad, Russell (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      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.
    • 2006 Evaluation of Commercial Harvest Aid Materials in Arizona Cotton Production Systems

      Norton, E. R.; Hatch, D. L.; Tronstad, Russell (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      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.
    • Arizona Upland Cotton Variety Testing Program, 2005

      Clay, P.; Norton, R.; Norton, E.; Nolte, K.; Taylor, E.; Husman, S.; Zerkoune, M.; White, K.; Tronstad, Russell; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      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.
    • 2006 Upland Cotton Variety Evaluations in Southeastern Arizona

      Norton, E. R.; Hatch, H. L.; Tronstad, Russell (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      Two separate Upland cotton variety evaluations were conducted in southeastern Arizona during the 2006 cotton growing season. One location was in Graham County (Thatcher), while the second location was in Cochise County (Kansas Settlement). Sixteen varieties were planted at the Thatcher and ten varieties were selected and planted at the Kansas Settlement location. Varieties ranged in maturity from early to full at each of the locations. All plots were arranged in a randomized complete block design with four replications. Both locations were planted on grower-cooperator fields and were managed in accordance to the individual grower styles. Plant measurements were collected over the course of the season at only the Thatcher location. Lint yield was determined by harvesting the entire plot at each location and weighing the resultant seedcotton. Sub-samples were collected also at the time of harvest for percent lint estimates and fiber quality analysis. Crop value was calculated multiplying the lint yield by a lint price determined by a base value of $0.52/lb plus any discounts or premiums based upon fiber quality. Lint yield levels at both locations were high ranging from 1200 to just over 1900 lbs. lint/acre with a new Acala variety from Phytogen (PHY745WRF) producing the highest yield and also the highest crop value at the Thatcher location. In Kansas Settlement lint yields ranged from 1000 to over 1500 lbs. lint/acre with the highest lint yield and total crop value being produced again by the new Acala variety from Phytogen (PHY745WRF).
    • 2006 Arizona Upland Cotton Advanced Strain Testing Program

      Norton, E. R.; Hatch, D. L.; Ellsworth, K. F.; Tronstad, Russell (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      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.
    • Assessment of Knack Field Performance Through Precision Field and Laboratory Bioassays in Cotton

      Ellsworth, Peter C.; Barkley, Virginia; Dennehy, Tim; DeGain, Ben; Ellingson, Bob; Naranjo, Steve; Sims, Maria; Tronstad, Russell; University of Arizona, Arizona Pest Management Center; USDA-ARS-ALARC (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      When a product performs better or worse than expectations, there are many biological, ecological, and operational factors that must be examined. Genetic resistance to the pesticide itself is often a concern. The control interval depends on the ecological impact of biotic (e.g., presence and function of natural enemies) and abiotic (e.g., frequency and severity of storms) factors. Timing, rates, and application methods used are also key factors affecting product performance. A four-year study to evaluate pyriproxyfen (Knack®) field performance in Arizona was initiated in 2004, after levels of whitefly susceptibility in statewide surveys were observed to be decreasing. Grower sites in Maricopa, Buckeye, Wellton, and Marana were used. We controlled for major operational factors by using a common timing, rate, and aerial application for each Knack spray. Resistance bio-assays were conducted on progeny of field-collected adults, pre- and post-spray. New eggs were marked in-field prior to spraying and examined in the field and lab in order to isolate Knack-associated mortality caused by direct toxicity as well as by ecological factors (e.g., bioresidual). Nymphal bioassays were used to evaluate metamorphosis inhibition. Population trends were estimated using standard sampling methods. Appropriate check plots were compared to the Knack treatment. Study results suggest Knack field performance and pyriproxyfen resistance has not changed significantly among the years or locations examined to date. In 2005, many struggled to gain control over whitefly populations. This work indicated that Knack performance and resistance parameters were within the range expected for the last several years. However, operational and ecological barriers to the performance of Knack and other chemistry were in play. Late planted conditions, lush winter vegetation capable of hosting whiteflies, poor growing conditions, and an extended period of extreme immigration pressure were all factors that diminished the impact of Knack and other products in 2005. In contrast, the winter preceding 2006 was among the driest on record followed by a very active monsoon season in central Arizona. High winds and dust movement, and a very active natural enemy community helped to continually lower whitefly populations. The result was a whitefly season characterized as light, with overall foliar insecticide usage setting a 28-yr record low for Arizona cotton. Barring all other operational and ecological factors at work, control intervals should have been similar each year. Yet, observed intervals have been different (e.g., 2005 vs. 2006) and point to the importance of these external factors in assessing product performance. Work will continue in 2007 to identify factors that contribute to whitefly outbreak conditions. These data will be key to understanding any performance changes, either due to operational or ecological factors mentioned above or due to innate changes in whitefly susceptibility. This will be important in advising growers about the risk factors associated with whitefly outbreaks and should lead to recommendations for minimizing these risks.
    • Economic Impact of Lygus in Arizona Cotton: A Comparative Approach

      Fournier, A.; Ellsworth, P. C.; Barkley, V. M.; Tronstad, Russell; University of Arizona, Arizona Pest Management Center, Maricopa, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      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.
    • 2006 Arizona Cotton Growers Association Breeding Program Advanced and Preliminary Strain Testing Program

      Norton, E. R.; Hatch, D. L.; Ellsworth, K. F.; Tronstad, Russell (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      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.
    • Residual Soil Nitrogen Evaluations In Irrigated Cotton, 2006

      Silvertooth, J. C.; Soto-Ortiz, R.; Norton, E. R.; Tronstad, Russell (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
      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.
    • Review of the 2006 Arizona Cotton Season

      Tronstad, Russell; Nolte, Kurt; Norton, Eric; Norton, Randy; Taylor, Erin; Tronstad, Russell (College of Agriculture, University of Arizona (Tucson, AZ), 2007-08)
    • Upland Cotton Variety Evaluations in Southeastern Arizona

      Norton, E. R.; Borrego, H. J.; Tronstad, Russell; Norton, E. Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2006-07)
      Three separate Upland cotton variety evaluations were conducted in southeastern Arizona during the 2005 cotton growing season. Two locations were in Graham County, Thatcher and Ashurst, while the third location was in Cochise County in the community of Kansas Settlement. Eleven varieties were selected for both the Thatcher and Kansas Settlement locations while seven were planted at the Ashurst location. Varieties ranged in maturity from early to full at each of the three locations. All plots were arranged in a randomized complete block design with four replications. All three locations were planted on grower-cooperator fields and were managed in accordance to the individual grower styles. Plant measurements were collected over the course of the season at both the Thatcher and Ashurst locations. Lint yield was determined by harvesting the entire plot at each location and weighing the resultant seedcotton. Sub-samples were also collected at the time of harvest for percent lint estimates and fiber quality analysis. Lint yield levels at both the Ashurst and Thatcher locations were high. Due to poor initial germination, the Kansas Settlement location had to be replanted and was later maturing. Thus, lint yield was down some from the normal average in that area. At the Thatcher location lint yield ranged from 1200 to just over 1600 lbs. lint/acre with ST5242BR producing the highest lint yield and the highest crop value. In Ashurst the yields ranged from 950 to nearly 1350 lbs. lint/acre with Fiber Max FM960RR producing the highest lint yield. However, due to some fiber quality discounts it did not produce the highest crop value. Fiber Max FM989RR had excellent fiber quality and produced the highest crop value even though it produced a slightly lower yield. In Kansas Settlement lint yields ranged from 460 to approximately 850 lbs. lint/acre with the highest lint yield and total crop value being produced by Deltapine DP444BR. This is consistent with the earlier nature of this variety.
    • Regional Extra Long Staple (ELS) Cotton Evaluation in Southeastern Arizona

      Norton, E. R.; Borrego, H. J.; Tronstad, Russell; Norton, E. Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2006-07)
      A single field trial was conducted in 2005 at the University of Arizona Safford Agricultural Center as part of the regional Extra Long Staple (ELS) cotton variety testing program. This trial was conducted to evaluate nine different ELS varieties under growing conditions of the Upper Gila River Valley. These nine varieties were planted in a randomized complete block design with four replications on 26 April 2005. All plots were managed in an optimum fashion with respect to general agronomic practices. Plot size was four rows 36” wide and 40’ in length. Lint yield was determined on 10 November by harvesting the center two rows of each plot and weighing the resultant seed cotton. Sub-samples were collected for percent lint determination and fiber quality analysis at the time of harvest. Lint yield averaged 1375 lbs/acre with a range of just over 1150 to nearly 1570 lbs lint/acre. Several experimental CPCSD varieties performed extremely well with E503 and E105 placing in the top three. The standard DP340 also placed in the top three. By comparison to the Pima S-7 variety significant advances in terms of yield are being made with the newer varieties being developed. Significant advances in fiber quality were also observed. Phytogen PHY800 performed very well with respect to fiber quality properties, particularly in comparison to the Pima S-7 standard of exceptional quality.
    • Pistil and Style Elongations Beyond the Anthers: Results From 2005 Field Experimentation

      Rethwisch, Michael D.; Luna, Manuel M.; Ramos, D. Michael; Wellman, Jessica J.; Williams, Michael T.; Tronstad, Russell; Norton, E. Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2006-07)
      A rapid heat increase from the high 80s-low 90s to high temperatures of 110o F on May 21 and 22, 2005, was recorded in the Blythe, CA, area, resulting in abnormal cotton flowers in mid-June, being especially characterized by elongated styles and stigmas being beyond the anthers. Two different cotton variety trials conducted in the Palo Verde Valley allowed data to be collected semi-weekly beginning June 17-20, with 100+ flowers per plot examined in each plot (four replications) of each of the 14 cotton variety entries. Every cotton variety had an average of 90+% of flowers expressing heat stress abnormalities (elongated styles) at the beginning of data collection even though the trials varied by planting date and location. Abnormal flowers were noted for several weeks, with some stigmas 21 mm beyond the anthers. Varieties differed in their responses to heat stress as measured by elongation later in the summer. Limited data were also collected for fruit retention and correlated with length of stigma extension beyond anthers. Retention percentages decreased as distance between anthers/stigmas increased, however boll size increased with less retention, possibly through nutrient partitioning. Various foliar fertilizers containing calcium were also evaluated for their effect on stigma elongations of DPL 449BR cotton. Significant differences existed for stigma elongations, with 2.5 qts./acre of CalMax resulting in statistical reduction of elongation when compared with the untreated check at 3 weeks after application. Statistical differences did not exist at four weeks although statistical differences did exist at this date for the percentage of flowers affected, with the highest percentage (81.7%) noted in untreated cotton.
    • A Review of 10 Years of Phosphorus Fertility Research in Arizona

      Norton, E. R.; Silvertooth, J. C.; Tronstad, Russell; Norton, E. Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2006-07)
      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.
    • Irrigation Termination Effects on Cotton Yield and Fiber Quality

      Silvertooth, J. C.; Galadima, A.; Tronstad, R.; Tronstad, Russell; Norton, E. Randy; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 2006-07)
      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.
    • Evaluation of Commercial Harvest Aid Products in Arizona Upland Cotton Production Systems

      Norton, E. R.; Borrego, H.; Tronstad, Russell; Norton, E. Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2006-07)
      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™.
    • Effect of Heat Unit Accumulation on Cotton Defoliation, Lint Yield and Fiber Quality

      Clay, P. A.; Young, K. M.; Taylor, E. R.; Tronstad, Russell; Norton, E. Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2006-07)
      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.
    • Evaluation of Various PPO Inhibitors as Defoliants for Upland Cotton

      Clay, P. A.; Young, K. M.; Taylor, E. L.; Tronstad, Russell; Norton, E. Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2006-07)
      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%).