• Search for Effective Chemical Controls for Lygus Bugs and Whiteflies in Arizona Cotton

      Barkley, Virginia; Ellsworth, Peter C.; Tronstad, Russell; Husman, Steve; Norton, Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2004-05)
      Whiteflies and Lygus bugs continue to be key pests of Arizona cotton. Some of our most popular and time-tested chemicals are still providing efficacy toward Lygus or whiteflies when used in a timely manner. However, promising new chemicals may also become available in the near future. Through research, growers can be kept updated on options for successful IPM. An experiment was conducted in order to expand our knowledge of currently available compounds and upcoming advances in insecticide development. In this experiment, 11 different compounds were tested for efficacy and duration of activity against whiteflies, Lygus, or both. Although none were active on Lygus adults, some chemicals were very effective on all stages of nymphs. Orthene® or Vydate® continue to show good results against Lygus but did not yield as high as one new compound. The best performing insecticide against Lygus was flonicamid, a novel chemistry under development by FMC. This insecticide had the best control over Lygus nymphs, was the highest yielding treatment, and required one less spray than other top performing compounds. Among newer chemistries for Lygus control is fipronil (Regent® by BASF), which performed slightly better than Vydate but not quite as effective as Orthene. Another higher-yielding regime included the use of novaluron, a novel insect growth regulator (IGR) scheduled for registration in 2005 (Diamond® by Crompton Corporation). This IGR was tested against whiteflies and Lygus bugs, but in light of yield data, Lygus efficacy should be examined more closely. None of the neonicotinoids were effective against Lygus, but several proved to be promising for whitefly control. Of the neonicotinoids tested and sprayed on threshold, dinotefuran (under development by Valent) showed good activity. The performance of spiromesifin (Oberon®, a new chemistry by Bayer) was similar to dinotefuran but needing one less spray. Intruder® out-performed all whitefly treatments, requiring only two sprays to control whiteflies season-long. Both Intruder or currently used IGRs (Knack® and Courier®) proved to be very effective against whiteflies. All insecticides in this test underwent very rigorous testing under extreme Lygus and whitefly pressures.
    • Short Staple Variety Trial in Virden, NM, 2003

      Clark, L. J.; Norton, E. R.; Tronstad, Russell; Husman, Steve; Norton, Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2004-05)
      This study is a continuation of the variety trials that have been grown in the Duncan/Virden area over many years to supply yield and revenue data on premium cotton varieties for local growers. In recent years, the introduction of herbicide resistant cultivars has been particularly interesting to help clean up many weedy fields. The premium quality New Mexico Acala varieties do not, at this time, have herbicide resistance traits and have struggled to produce high enough yields to compete with the lower quality varieties that are available. Fifteen cotton varieties were tested including two 1517 varieties from New Mexico, Sierra, the newest Roundup-Ready from CPCSD, Salcot Sacala, a new acala from Arizona, and the AZ Cotton Growers variety. The rest of the entries were Roundup-Ready short to mid season varieties from Delta Pine, Stoneville, FiberMax and Paymaster. The highest yielding variety in the trial was Riata, a Roundup Ready Acala from CPCSD, with a yield of 1255 pounds of lint per acre. Sierra, ST 5599RR, ST 5303R and 1517- 99 produced around 100 pounds less lint per acre than Riata but the yields were not statistically different. Plant heights, first fruiting branches (FFB), total nodes and boll weights were measured and height to node ratios were calculated. Many differences were seen between varieties with all of these variables. The values of the variables defining the characteristics of the varieties. HVI data were obtained for fiber qualities of the lint of each variety. This data was then used to determine the value of the lint and then estimate the gross revenue produced by each variety. The highest lint value (cents per pound) was produced by 1517- 99 with 1517-95 and Riata following closely behind. The highest gross revenue was produced by Riata as a combination of the high yield and high lint value.
    • Update on Pink Bollworm Resistance to Bt Cotton in the Southwest

      Dennehy, Timothy J.; Unnithan, Gopalan; Brink, Sarah A.; Wood, Brook D.; Carrière, Yves; Tabashnik, Bruce; Antilla, Larry; Whitlow, Mike; Tronstad, Russell; Husman, Steve; et al. (College of Agriculture, University of Arizona (Tucson, AZ), 2004-05)
      Monitoring of Arizona pink bollworm (PBW), Pectinophora gossypiella, susceptibility to the Bt toxin Cry1Ac has been conducted annually since 1997. PBW were collected from cotton fields located throughout the Southwest in 2002, cultured in the laboratory, and tested for susceptibility to Cry1Ac using diet-incorporation bioassays. A total of 13 Arizona collections were successfully reared and bioassayed. Collections from California (6), New Mexico (1), and Texas (1) were also tested. Laboratory selection of pink bollworms collected from Arizona in 1997 and exposed to Cry1Ac in diet produced a strain capable of surviving on Bollgard® cotton. Subsequent studies showed that 10 g Cry1Ac/ml of insect diet was a reliable diagnostic concentration for detection of pink bollworm that were homozygous for resistance to Cry1Ac. On this basis, resistant PBW were detected in 2002 in only 2 out of 13 Arizona strains. The overall frequency of resistant PBW in 2002 for Arizona was 0.17% and ranged from 0.0 to 1.7%. One of six California collections evaluated had a single resistant survivor. No resistant pink bollworms were detected in the single New Mexico and Texas collections evaluated. Resistant PBW were significantly more abundant in Arizona in 2001 and 2002 than they were in 1998, 1999 or 2000. However, the frequency of resistant survivors in bioassays was low for 2001 and 2002, and markedly lower than in 1997. The Arizona Cotton Research and Protection Council evaluated the efficacy of Bt cotton in 2002 using adjacent pairs of Bt and non-Bt fields at 43 locations across Arizona. Pink bollworms were found in an average of 23.3% of these non-Bt boll fields. Bolls from Bt cotton fields yielded an average of 0.144% (range 0 to 1.300%) infested bolls. Of these, all but three of the pink bollworm recovered from Bt cotton plantings came from bolls that tested negative for Cry1Ac. We conclude from these findings that there is no indication that pink bollworm resistance to Cry1Ac was a problem at the locations sampled in 2002. Bt cotton continued to exhibit exceptional field performance in Arizona.
    • Upland Cotton Variety Evaluation in Graham County, 2003

      Norton, E. R.; Clark, L. J.; Tronstad, Russell; Husman, Steve; Norton, Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2004-05)
      A field trial was established during the 2003 growing season as part of the statewide Upland Cotton Variety Testing Program. This trial was located in Thatcher with Dennis Layton Farms as the cooperator. The location was one of eleven around the state. A total of twelve varieties were entered from six cooperating seed companies. Varieties included DP655BR, DP555BR, DP449BR, and DP5690R from Delta and Pine Land Company; FM989BR, FM991R, and FM991BR from Fiber Max; ST5303R and ST5599BR from Stoneville; Riata from CPCSD; AG3601 from Arizona Cotton Growers Association; and SCX-7 from Salcot. The twelve varieties were planted in a randomized complete block design with three replications. Individual plots consisted of 4, 38” rows extending the full length of the irrigation run (1250 ft.). Plant measurements were collected throughout the season to evaluate growth and development characteristics of each variety. Yield and fiber quality data was collected at the end of the season by harvesting and weighing each individual experimental unit. Sub-samples were collected for fiber quality analysis. Percent emergence data indicated differences in seedling vigor and stand establishment. Percent emergence ranged from a high of nearly 90% (Fiber Max FM989BR) to less than 50% (Delta and Pine DP555BR). Even with the low percent emergence for DP555BR an adequate stand was achieved for each variety and did not significantly impact final yield. Significant differences were observed in final lint yields with Fiber Max FM991BR producing the highest yield at 1690 lbs. lint per acre and Fiber Max FM989BR producing the lowest yield at 1292 lbs. lint per acre, a difference of approximately 400 lbs. Delta and Pine DP655BR has been the standard variety planted in the valley for several years. The only variety producing more lint than DP655BR was FM991BR. Lint value calculated using premium/discounts for fiber quality resulted in FM991BR with the highest value at $952/acre. All varieties had overall premiums except for AG3601which was discounted due to high fiber micronaire. Results from this evaluation indicate that FM991BR appears to be an additional variety from which growers have to choose that has the potential to perform very well in the Upper Gila River valley.