• Preliminary Evaluation of the "Next Generation" of Bt Cotton

      Sieglaff, D. H.; Ellsworth, Peter C.; Silvertooth, Jeffrey C.; Hamilton, E.; Silvertooth, Jeff; The University of Arizona, Department of Entomology & Maricopa Agricultural Center; Department of Plant Sciences; Monsanto Company, Chesterfield, MO (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      The next generation of Bollgard® cotton was evaluated for agronomic and insecticidal efficacy under central Arizona growing conditions. Two novel lines were compared with their recurrent parents, DP50 and DP50B. There were no seasonlong differences observed among the varieties in most plant development and insect parameters. However, DP50 had significantly lower emergence than the other lines tested (possibly related to seed quality). The lower plant population may have been responsible for greater whitefly abundance observed on two dates mid-season. During early-season ratings of secondary “pests” (15 DAP) (scaled on damage and/or presence), the two test lines received lower ratings for thrips and flea beetle when compared with DP50, DP50B and DP50Bu (untreated for Lepidoptera). However, these difference are likely as a result of the difference in seed treatments that the two test lines received (Gaucho®) and the others did not. This seed treatment does have known activity against thrips and beetle pests. In mid-season, the two test lines received lower ratings for beet armyworm when compared to DP50, DP50B and DP50Bu (although, not significantly different from DP50B or DP50Bu). Efficacy against pink bollworm (PBW) was assessed one time at the end of the season (we were limited to this time, so as to not affect yield), and DP50 was the only variety in which PBW exit holes were observed and PBW larvae collected. However, the low Lepidoptera pressure experienced during the season limited assessments of the two novel lines’ efficacy toward PBW. There was no significant difference in yield (bale/A) among the varieties. Although, one of the test lines had a lower lint turnout than each other variety. The two novel Bollgard lines performed well under our growing conditions, but continued evaluations will be necessary under more conditions and more insect pressures before “varietal” performance and gene efficacy can be assessed adequately.
    • Preplant Micronutrient Fertilizers for Cotton

      Knowles, Tim C.; Artz, Paul; Sherrill, Chip; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Micronutrient fertilizers including zinc, boron, copper, and manganese in their sulfate forms were broadcast applied and incorporated preplant to determine their effects on lint yield of upland cotton.
    • Short Staple Regional Cotton Variety Trial, Safford Agricultural Center, 1998

      Clark, Lee J.; Carpenter, E. W.; Hart, G. L.; Nelson, J. M.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Forty eight short staple varieties were grown in a replicated field trial on the Safford Agricultural Center. Excellent yields were recorded, especially considering the late start caused by unseasonably cold weather in April. FM 989, the Australian variety formerly known as IF 1003, produced the highest lint yield of 1601 pounds per acre. Three other varieties, FM 975, AP 4103 and IF 1002, produced over 1500 pound of lint per acre. Agronomic values for the plants at harvest and HVI data for lint quality are tabulated in this paper.
    • Short Staple Variety Trial, Greenlee County, 1998

      Clark, Lee J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Six short staple cotton varieties including two New Mexico acalas varieties and one advanced strain, an Australian varieties and two SureGrow varieties with higher yield potential were tested in this study. New Mexico Acala 1517-95 had the highest lint yield with a yield of 419 pounds of lint per acre. The average yield was about 400 pounds per acre lower than the 6 year average due to a cold spring and a four inch rain that fell in one hour in the middle of July. In addition to lint yields; percent lint, plant heights, plant populations and lint hvi values are shown. A lint yield comparison for 1993 through 1998 is included in this paper.
    • Short Staple Variety Trials in Cochise County, 1998

      Clark, Lee J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Variety trials were grown at two locations and with two different sets of short staple varieties. One trial on the Robbs farm, north of Kansas Settlement, tested two acala varieties and the most promising advanced strain from New Mexico, two short seasoned varieties from SureGrow and one Australia variety. The other trial on the Glenn Schmidt farm, in Kansas Settlement, tested seventeen upland varieties as part of the statewide testing program. The highest yielding variety in the Robbs trial was SG 404 with SG 125 coming in second. In the Schmidt trial, FM 989, an Australian variety that has performed well in Safford, had the highest yield, just over 2 bales per acre.
    • Short Staple Variety Trials, Graham County, 1998

      Clark, Lee J.; Carpenter, E. W.; Walser, R. H.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Two replicated on-farm short staple variety trials were planted in 1998. Fifteen varieties were evaluated on both the Carpenter farm in Thatcher and the Colvin farm near Ft. Thomas. Several new varieties were planted in both studies, including 4 transgenic varieties: DP 90B, BXN 47, DP 90RR and Paymaster 1560BG, 2 varieties from Australia: FiberMax 989 and FiberMax 832, and seven other varieties seen for the first time. Two of the new varieties produced the highest yields; AgriPro 6101 and Phytogen 952 on the Carpenter and Colvin farms, respectively. Other agronomic data from the varieties and HVI values from the lint are also included in this report.
    • Systemic Insecticide Applications at Planting for Early Season Thrips Control

      Knowles, Tim C.; Bushong, Neil; Lloyd, Jim; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Temik 15G (6 lbs/acre) or Thimet 20G (8.2 lbs/acre) granular insecticides were applied to 40 inch rows in furrow at planting to cotton growing in Parker Valley, AZ. Moderate thrips pressure (0.5-1.5 thrips/plant) was experienced for the first eight weeks after planting and granular insecticide application. Temik provided better thrips control than Thimet for the first seven weeks after planting this study. Thrips control was similar for the two insecticides beyond eight weeks after planting. Temik application resulted in higher fruit retention levels measured up to 10 weeks after planting, compared to Thimet. However, fruit retention levels measured from 12 to 16 weeks after planting were similar for both Temik and Thimet when cotton plants compensated for early season square losses caused by thrips feeding.
    • Upland Cotton Lint Yield Response to Several Soil Moisture Depletion Levels

      Husman, Stephen H.; Johnson, K.; Wegener, R.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Upland cotton lint yield response to several soil moisture depletion levels was measured in 1997 and 1998. In 1997, four Upland cotton varieties including DP 5415, DP 33B, DP 5816, and STV 474 were tested. However because of a nonsignificant variety difference in the 1997 test, the 1998 test was planted to a single variety (DP 33B). In 1997 and 1998, depletion of plant available soil water (PAW) irrigation treatments consisted of 35%, 50%, 65%, and 80%. In 1997, all PAW depletion treatments were significantly different with the 35% PAW treatment resulting in the highest average lint yield of 1880 lbs. lint/acre. The 50%, 65%, and 80% PAW treatments resulted in 1410, 1123, and 248 lbs. lint/acre respectively. There was no significant (P<0.05) difference between varieties within all PAW treatments in 1997. In 1998, all PAW depletion treatments again were significantly different with the 35% PAW treatment resulting in the highest average lint yield of 1658 lbs. lint/acre. The 50%, 65%, and 80% PAW treatments resulted in 1534, 1396, and 641 lbs. lint/acre respectively.
    • Upland Regional Cotton Variety Test at the Maricopa Agricultural Center, 1998

      Hart, G. L.; Nelson, J. M.; Clark, Lee J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      Thirty six upland cotton varieties were grown at the Maricopa Agricultural Center as part of the national cotton variety testing program. Lint yield, boll size, lint percent, plant populations, plant heights and fiber properties are presented in this paper.
    • Whitefly Management with Insect Growth Regulators and the influence of Lygus Controls

      Ellsworth, Peter C.; Naranjo, Steve E.; Silvertooth, Jeff; The University of Arizona, Department of Entomology & Maricopa Agricultural Center; USDA-ARS, Western Cotton Research Laboratory, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1999)
      The three keys to whitefly management are sampling, effective chemical use, and avoidance. This study examines factors relevant to the latter two keys in the context of Arizona’s cotton pest spectrum. Insect growth regulators (IGRs) are central to Arizona’s success in whitefly management. The basic usage guidelines developed for the IGRs—initial treatment timing, prescribed intervals between successive uses, and one use each seasonal limits—are all valuable in the development of a sustainable use pattern. Re-treatment timing guidelines for the second IGR has been the subject of investigation for the past two years. However, whitefly pressure in 1998 was strikingly different and lower than in any other post-introduction year. Re-treatment was unnecessary and thus could not be evaluated this year. Lygus, on the other hand, were at damaging levels early in plant development and for a protracted period. Future successes in whitefly management should consider the whole pest spectrum and depend on integrating chemical controls for all sprayed pests. While our primary focus is to optimize management of whiteflies in the context of other pests, this study examined the impact of Lygus controls on whitefly population dynamics and cotton production. Three sprays were required to control Lygus populations in this study. These sprays were atypically non-disruptive to whitefly population dynamics, and instead, helped to suppress low-level populations of whiteflies even further. This lack of disruption may have been due in part to the reduced abundance and role of natural enemies in this study. Lygus sprays did protect yields with a 3-fold advantage over untreated plots. Furthermore, there were a series of negative consequences of poor Lygus control. Plants tended to be more vegetative and more difficult to defoliate. Lower lint turnouts were documented for the Lygus-untreated areas. Sources of this additional loss were identified and included increased gin trash and larger seed size in Lygus-untreated areas. The lint also had significantly more sticking points as measured by manual thermodetector. While all cotton was determined to be non-sticky, this increased contamination may have been also related to the higher trash levels. Because of the differences in outcome in 1997 and 1998 in terms of Lygus spray effects on whiteflies, it is even more imperative that we further test whitefly management systems under near commercial conditions. A better understanding of the relationship between the control programs for these two major pests will help guide decisions on remedial inputs. This study also serves as an annual, replicated, and systematic accounting of whitefly population dynamics and control requirements useful for making historical comparisons across years. Inferences may be drawn about what are and are not the underlying causes of the unusual population dynamics observed in 1998.