• Irrigation Efficiencies, Nitrogen and Phosphorous Applications, and Lint Yields of Upland Cotton Grown at the Maricopa Agricultural Center, 1992

      Sheedy, Mike; Watson, Jack; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The computer program AZSCHED, with weather data obtained from AZMET, was used to schedule irrigations for a yield trial of Upland Cotton (DPL 90) at the Maricopa Agricultural Center. Cotton lint yields were compared between plots from eight treatments involving the combination of two irrigation efficiencies (70% and 90%), two nitrogen fertilizer placements (sidedressed and broadcast), and two phosphate fertilizer applications (0#/a and 50#/a). A potassium bromide (KBr) tracer was applied to select areas in each plot prior to the first irrigation. The total amount of fertilizer as nitrogen applied in split applications to both the sidedressed and broadcast plots was 120 #/a. The average amount of water applied to the plots were 33.5" for 70 % efficiency and 26.9" for 90% efficiency. Soil samples from each KBr applied plot were taken to a depth of 10' for analysis of bromide and nitrate to determine the depth of water movement through the soil profile. The plots were harvested on October 7, 1992. This year there was no significant difference in lint yield between any of the treatments: irrigation efficiencies, nitrogen placement, or phosphorous application.
    • Trap Crops as a Component of a Community-Wide Pink Bollworm Control Program

      Thacker, Gary W.; Moore, Leon; Ellsworth, Peter C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Trap crops were employed against the pink bollworm (PBW) as a part of a community-wide IPM program in Pima County, AZ. Levels of PBW larvae in the early squares of the trap crops were extraordinarily high, indicating that the trap crops were drawing overwintered PBW moths in from wide areas. This concentrated the overwintered moths in small areas where they could be easily and economically destroyed.
    • Sweetpotato Whitefly in Arizona

      Ellsworth, P. C.; Diehl, J. P.; Silvertooth, J. C.; Brown, P. W.; Watson, T. F.; Hood, L. R.; Husman, S. H.; Thacker, G. W.; Clark, L. J.; Cluff, R. E.; et al. (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Whitefly management has become a complex objective in Arizona in the past several years. A tremendous amount of research and extension effort is now focused on this significant pest. The purpose of this paper is to describe the position and guidelines of the University of Arizona's Cotton Team regarding the Sweetpotato Whitefly. The information presented is credited to no single source, but represents a collection of information from numerous research and extension scientists within and outside of the U of A system and careful analyses of the presently available data on whitefly management dynamics. Where possible, only the results of research are reported and suggestions based only on experience or speculation are duly noted.
    • The Development and Delivery of a Crop Monitoring Program for Upland and Pima Cotton in Arizona

      Silvertooth, J. C.; Brown, P. W.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      A crop monitoring program has been developed specifically for varieties and environmental conditions unique to Arizona. The monitoring program involves early season development guidelines, growth stage guidelines, and in- season evaluation of crop condition (vegetative /reproductive balance and fruit retention), by use of simple measurements such as height:node ratios (HNR), nodes above the top white bloom (NAWB) counts, and fruit retention estimates from plant mapping. The preliminary work necessary in terms of providing accurate and precise descriptions of the various crop development parameters has been provided through a detailed cotton phenology project conducted over many site years of experimental work. The resultant baselines describing crop development /monitoring parameters have been scaled as a function heat unit (HU, 86/55° F thresholds) accumulations. Application of these baselines have been developed through another facet of the research program to provide a basis for a feedback approach to crop management for inputs such as water, nitrogen (N), plant growth regulators, etc.. The crop monitoring program serves as a fundamental component to an active extension education program being delivered on a statewide basis to all cotton producing areas in Arizona.
    • Sweetpotato Whitefly (Bemisia tabaci Gennadius) Control: Field Studies with Insecticides on Cotton in the Imperial Valley, CA

      Chu, C. C.; Henneberry, T. J.; Akey, D. H.; Silvertooth, Jeff; Western Cotton Research Laboratory, USDA -ARS, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Insecticides and insecticide mixtures were evaluated for sweetpotato whitefly (Bemisia tabaci Gennadius) control on cotton in the Imperial Valley, CA in 1992. Seasonal average number of large immatures was 1.6/cm² leaf disk from plots treated with a mixture of Danitol and Orthene as compared to 4. 5/cm² on leaf disks from untreated control plots. Lint yield was 1232 lbs/ac compared to other treatments which ranged from 551 to 976 lbs /ac.
    • The Effect of Water Stress on Two Short-Season Cultivars of Cotton, Gossypium hisutum L., and the Sweetpotato Whitefly, Bemisia tabaci Genn

      Flint, Hollis M.; Wilson, F. D.; Hendrix, D.; Leggett, J.; Naranjo, J.; Henneberry, T. J.; Radin, J. W.; Silvertooth, Jeff; Western Cotton Research Laboratory, USDA -ARS, Phoenix, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Deltapine 50 (DP -50) and Stoneville 506 (ST -506), short season cultivars of upland cotton, Gossvpium hirsutum L., were grown under weekly or biweekly irrigation schedules in 0.2 ha plots in a split plot design at Maricopa, AZ. The seasonal average numbers of sweetpotato whitefly eggs and nymphs were 24% greater on leaves of plants irrigated biweekly. The leaves of ST-506 had 26% greater numbers of eggs and nymphs than did leaves of DP -50. Samples of lint from the two cultivars irrigated biweekly had 32 % more sugar than did lint from the cultivars irrigated weekly (weekly = 0.28 ± 0.02% , biweekly = 0.41% ± 0.03% sugar). Our results indicate that the numbers of immature sweetpotato whitefly on cotton plants can be reduced by 47% by selecting a less susceptible cultivar and avoiding plant water stress.
    • Weather Conditions during the 1992 Growing Season

      Brown, P.; Russell, B.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Abundant rainfall was the most prominent feature of the 1992 growing season. Monthly precipitation totaled above normal during the first five months of the year, and during August and December. Warm temperatures accompanied the wet weather during the spring planting season and helped boost growing season heat unit totals to near record levels in central and western Arizona. Early fall weather was warm and dry which provided excellent conditions for both finishing the crop and preparing the crop for harvest.
    • Cotton Row Spacing Study on Long and Short Staple Cotton, Safford Agricultural Center, 1992

      Clark, Lee J.; Carpenter, Eddie W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      A row spacing study was conducted on both long and short staple cotton on the Safford Agricultural Center. The results of this study showed that yields increased from the narrower spaced rows (36 -30 inch and 30 inch spacings) to the wider spaced rows (36 inch and 40 inch spacings). This is the same trend as reported previously with long staple cotton but differs from that previously reported for short staple cotton. Yields of 1.67 and 25 bales per acre for long and short staple cotton were reported.
    • Cottonseed Treatment Evaluations in Arizona, 1992

      Silvertooth, J. C.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Field experiments were conducted at three locations in Arizona (Maricopa, Marana, Safford) to evaluate 9 cottonseed treatments on Upland cotton (G. hirsutum L.). Stand counts were taken to evaluate the effectiveness of each treatment. Statistical analysis showed no significant differences among the treatments used at the Maricopa location. Significant differences were found among the treatments used at the Marana and Safford locations.
    • Pima Regional Cotton Variety Test, Maricopa Agricultural Center, 1992

      Nelson, J. M.; Clark, L. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Twelve pima varieties were grown in a replicated trial at the Maricopa Agricultural Center as part of the National Cotton Variety Testing Program.
    • Cotton Farmer Ratings of Tillage Systems: Important Characteristics and Perceptions of Alternate Systems

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      In a mail survey, we asked Arizona cotton growers which characteristics of a tillage system are important to them. Burial of crop residue, low cost, easy maintenance, reliability, low field work time, and breaking insect life cycles were all rated as important characteristics. Dust control was rated as not important. In rating their perceptions of conventional and alternative tillage systems, cotton farmers indicated that they were not completely satisfied with any of the currently available tillage alternatives.
    • Management of Pre-Harvest Aflatoxin Contamination of Cottonseed Using Beneficial Bacteria

      Misaghi, I. J.; Cotty, P. J.; DeCianne, D. M.; Silvertooth, Jeff; Department of Plant Pathology, University of Arizona; USDA/ARS, Southern Regional Research Center (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The overall goal of our study is to find effective and environmentally sound methods to reduce pre -harvest aflatoxin contamination of cottonseed in Arizona. The specific objectives are: 1) to screen a large number of bacteria for their ability to destroy the aflatoxin producing fungus, Aspeigillus flavus; 2) to test the efficacy and consistency of the recovered antagonistic bacterial isolates to reduce aflatoxin contamination of cottonseed in field trials; 3) to study the survival and competitiveness of the antagonists on cotton plants under prevailing field conditions; 4) to find innovative procedures to enhance survivability and competitiveness of the antagonists on cotton plants; and 5) to test the potential of the bacterial antagonists to reduce the population of A. flavus in field soils. Over 800 bacterial isolates, recovered from cotton field soils, cotton leaves, stems, and immature as well as opened bolls, were tested for ability to inhibit the growth of A. flavus on cottonseed. Six isolates partially or totally inhibited the fungus. All of these effective isolates prevented the fungus fioin infecting simulated pink bollworm exit holes in immature bolls in the field.
    • Progress on the Use of Trap Crops for Whitefly Suppression

      Ellsworth, P. C.; Meade, D. L.; Byrne, D. N.; Draeger, E. A.; Chernicky, J. P.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      In 1992, a repeat of a trap -cropping experiment was conducted for the suppression of sweetpotato whiteflies in Pima (S-6) cotton (see Ellsworth et al. 1992). The 1991 experiment showed some promise, but was characterized by low to moderate and later infestations of whiteflies than was desired. The 1992 experimental design (land area = 9.5 acres) was modified to accomplish three improvements: 1) the cotton crop area was doubled in size to 8 rows by 50 ft to improve the ratio of crop to trap area, 2) a fourth treatment was added to form a Latin square design which consisted of cotton plots surrounded only by bareground (i.e., no trap crop): the other three were surrounded by Wright groundcherry that was untreated or treated with 1X or 2X rates of soil-applied aldicarb, and 3) melons (1 row X667') were late planted between blocks to ensure locally abundant whiteflies during the time of the test. The melons were watered regularly in order to retain whiteflies until the start of the test. Early groundcherry establishment was variable and later compromised by insufficient water. This prompted later than usual flushes of groundcherry growth and delayed canopy development. This fact coupled by the intense level of whitefly movement following melon dry -down effectively overwhelmed the insufficiently developed trap crop. Aldicarb was applied on two dates (7/29 & 8/15), and whiteflies were sampled from all plots five times through August. The sampling data are preliminary at this point, but several observations were apparent: 1) the groundcherry trap crop was insufficiently developed to protect the Pima crop, 2) the addition of melons to the system dramatically increased the ,cumbers of locally abundant whiteflies, 3) maintaining the melons in good condition (i.e., well- watered) effectively retained whiteflies in the melons until dry-down, 4) upon dry-down, the melons released overwhelming numbers of adult whiteflies which could not be suppressed on the groundcherry trap crop before reaching the adjacent cotton, 5) the groundcherry was still selectively attractive to the whiteflies (relative to cotton), but was insufficiently developed w trap and retain the huge numbers of dispersing whiteflies, 6) soil - applied aldicarb did accomplish some degree of control of whiteflies on the groundcherry plants, but was inadequate in the face of the tremendous immigration of whitefly adults, 7) the intense whitefly pressure ultimately killed the majority of immature groundcheny plants with the aldicarb-treated plants lasting somewhat longer than the untreated plants, and 8) the yield and quality of the adjacent, late -planted Pima crop was commercially unacceptable and judged to be virtually a total loss. The failure of this implementation of the trap -cropping concept does not preclude the possibility that a better implementation would have succeeded; however, the observation that melons in close proximity to the test area dramatically changed the number of locally dispersing adult whiteflies cannot be denied. It would seem unlikely that a suitable trap crop system could be developed where such an intense proximate source and near instantaneous release of thousands of whiteflies (i.e., at dry-down of melons) is occurring.
    • Drought Tolerance in the Progeny of Interspecific Cotton Hybrids

      McDaniel, R. G.; Dobrenz, A. K.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The F2 and F3 progeny of interspecific cotton crosses were evaluated under field conditions. The plants were maintained under drip irrigation with stress applied by withholding water during plant development and early flowering periods. Physiological and biochemical plant responses were measured throughout the growing season on an array of representative plants from the field population. Considerable variability was found to exist among these progeny for all traits measured in both years of the present study. Responses of parental controls were quite consistent for both seasons.
    • Expression of Insectical Protease Inhibitors in Arizona Cotton

      Thomas, John C.; Bohnert, Hans J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Insect damage impacts tremendously on the value of the Arizona cotton crop. As traditional pesticides become increasingly less useful, due to insect resistance and regulatory problems, new methods for insect control are needed. For these reasons, we engineered genes encoding protease inhibitors (PIs) from Manduca sexta (tobacco hornworm), for expression in cotton, with the hope that these inhibitors would have insecticidal activity. Transgenic plants containing PIs have been generated: 22 fertile lines of the duplicated 35S promoter anti-elastase, 4 fertile lines of the anti -chymotrypsin and 5 fertile lines of the anti -trypsin. Over 3,000 T-1 seeds have been collected and T-2 generation seeds are in production. Many crosses have been made into Delta Pine 16, 90 and 5415 respectively. No significant effect of the PIs on boll number or seed yield was observed. Insect tests have been conducted and the results indicate that plants expressing the protease inhibitors (PI's) have decreased emergence of whiteflies compared to control plants. We believe this research is a significant step towards a bio- pesticide producing Arizona cotton variety.
    • Germination and Respiration of Cotton Seed Produced in Arizona

      Dobrenz, Albert K.; Silvertooth, Jeffrey C.; Martin, Jill; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The germination percentage and seedling respiration were evaluated on 11 cultivars of Cotton produced in Arizona. Respiration rates of 5-day old seedlings ranged from 6.0 to 16.9 mg /g⁻¹ hr⁻¹ for DP -5690 and KC-311, respectively. Germination percentage ranged from 31 to 87% for KC-311 and DP-51, respectively. A significant negative correlation (r = -.90) between respiration rates and the germination percentage indicates that seed quality is closely associated with early seedling metabolic rates.
    • Sequential Sampling Plans for Bemisia Tabaci Eggs and Nymphs in Cotton

      Naranjo, Steve E.; Flint, Hollis M.; Silvertooth, Jeff; USDA, ARS, Western Cotton Research Laboratory (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Fixed precision sequential sampling plans are reported for egg and nymphal stages of Bemisia tabaci on cotton. These plans were developed based on detailed examination of within -leaf, within plant, and within field distributions of egg and nymphal (crawler through pupae) stages during the 1992 growing season in central Arizona. The most efficient sample unit for eggs and nymphs was determined to be a single 3.88 cm2 circular plug taken from the basal portion of the 2nd sector of the 5th mainstem node leaf (counted from the terminal). Tentative plans are presented relating cumulative counts to sample size for fixed levels of precision.
    • The Concept of Controlled Traffic Tillage

      Thacker, Gary W.; Coates, Wayne E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      With controlled traffic tillage, the field is divided into "traffic zones" to which all wheel traffic is confined and `production zones" where the plants are grown and there is no wheel compaction. Researchers have shown that using this concept can result in significantly lower tillage costs and field work time than with conventional "broadcast" tillage systems. Most researchers have shown that controlled traffic cotton yields are as high, and are sometimes higher than with conventional tillage. In our research, we have not measured any differences in yield or soil compaction between controlled traffic and conventional tillage systems.
    • Chemical Control of the Sweetpotato Whitefly in Cotton

      Watson, Theo F.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      Both registered and experimental insecticides were evaluated for effectiveness against the sweetpotato whitefly in several field experiments at Yuma, Arizona. Best results were obtained with combinations of two insecticides, particularly a pyrethriod and an organophosphate, rather than with individual materials. Results of these experiments indicate that unusually heavy infestations can be currently controlled even though sustained use of these insecticides would probably lead quickly to the development of resistance.
    • Effect of Foliar Applications of PGRIV on Yield of Pima and Upland Cotton

      Nelson, J. M.; Hart, G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1993-03)
      The commercial product PGRIV was tested in small plots on cotton at the Maricopa Agricultural Center. Multiple foliar applications of this product had no significant effect on lint yield of Pima S-7 and DPL 90 cotton.