• A Native Weed as a Trap Crop for Whiteflies in Cotton

      Ellsworth, Peter C.; Chernicky, Jon P.; Byrne, David N.; Gibson, Roberta; Meade, Donna; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A field study was conducted during 1991 to evaluate the effectiveness of Physalis wrightii Gray, as a trap crop for Bemisia tabaci (Gennadius) when grown with the commercial crop Gossypium barbedense L. Aldicarb at two rates was used in P. wrightii for control of B. tabaci. Three sampling methods: pan counts, leaf turns, and leaf counts measured B. tabaci numbers in both crops. Aldicarb treatment in the trap crop did significantly affect B. tabaci populations in comparison with untreated P. wrightii (P= 0.000, df =2, 240). Differences in numbers of adults observed on the two hosts were not significant. Analysis of aldicarb metabolite residues by high pressure liquid chromatography exhibited a pronounced dose effect (P= 0.001, df =2, 22) in the trap crop leaf tissues. The chemically treated trap crop did significantly protect the cotton crop from larger and more rapidly developing sweetpotato whitefly populations when compared to the untreated check.
    • Weather Conditions during the 1991 Growing Season

      Brown, P.; Russell, B.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      The 1991 growing season was characterized by a cool, wet spring and a cool, dry summer. Heat unit accumulation for the season was the lowest in 5 years at most locations. Precipitation was concentrated in two periods: early (Jan. - Mar.) and late (Nov. - Dec.). Summer rainfall was well below normal at most locations.
    • IPM Cotton Projects, Safford Agricultural Center 1991

      Clark, Lee J.; Carpenter, Eddie E.; Kelly, Suzanne; Watson, Theo; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      In 1991 four Insect Pest Management studies were conducted to help understand the pink bollworm and aid in its control. The first two were replicated cage studies where cages were placed over the soil and insect emergence from the soil was monitored several times a week from January to mid-summer. The first had pink bollworm (pbw) infested bolls buried at 0, 2, 4 and 8 inches under the soil. The second had four plow down dates and sub -treatments of one or no irrigations. Perhaps due to the cold winter, few pink bollworm moths emerged in either study. In the buried infested boll study, no bolls buried at 8 inches produced pink bollworm moths in the spring and few emerged from either 4 or 2 inches. Of the bolls left on the surface, there was emergence from only some of the replications. Less than 1% of all of the potential moths emerged. In the plowing test, only 6 pink bollworms emerged in any of the 32 cages placed in the plots over the 18 weeks of the study. It appears to be a numbers game and the chance of having a pink bollworm emerge under a randomly placed cage in a field is very small. The second two tests involved Trichogramma bactrae, a trichogrammatid species imported from Australia. The first of these two studies involved placing laboratory produced pink bollworm eggs in a pattern around a release site for the parasitic wasps to determine their area of influence. This was done on three different occasions with varying success. The study was complicated by the fact that the wasp hatch must be coordinated with the pink bollworm egg deposition. Never-the-less, some pink bollworm egg parasitization took place. This study needs to be repeated. The second of these studies was two plots side-by-side, one treated with chemicals to control pink bollworm (and other insects), the other with weekly trichogramma releases during August and September. At the end of the season, 20 plants were removed from each plot and boll infestation and boll load were determined. The parasite controlled plots had a higher infestation level (35% to 23% with an LSD(05) of 9.9) than the chemically treated plots. There was no difference in the boll load between the two treatments. This study should be continued, preferably with a check plot so the value of the trichogramma can be evaluated more accurately.
    • Cotton Yields: Nitrogen and Harvest Aid Effects

      Chu, Chang-chi; Henneberry, Thomas J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      The results of field studies with N rates from 0 to 336 kg/ha, in combination with two growth regulators, ethephon (Prep® ɑ-chloroethyl phosphonic acid, Rhone-Poulenc Ag Co., Research Triangle Parr NC) and thidiazuron (Dropp® N- phenyl -N' -1,2,3 -thiadiazol -5ylurea, Nor-Am Ag Prod. Inc., Naperville, IL). Results showed that sidedress applications of N (ammonium nitrate) to cotton did not influence the defoliation effects of ethephon and thidiazuron, or reduce number of immature green bolls at harvest. Under short-season conditions, sidedress N applications did not effect yields. Ethephon and thidiazuron at the rates tested did not affect cotton lint yields. Thidiazuron alone or in combination with ethephon resulted in high percentages of cotton defoliation.
    • The Use of AZSCHED to Schedule Irrigation on Cotton, Safford Agricultural Center - 1991

      Clark, Lee J.; Carpenter, Eddie W.; Slack, Donald C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Irrigation scheduling software has been developed that is menu driven, user friendly and capable of scheduling up to 60 fields. This software is demonstrated scheduling irrigation on both Pima and upland cotton in this paper.
    • Cottonseed Treatment Evaluations in Arizona, 1991

      Silvertooth, J. C.; Malcuit, J. E.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Field experiments were conducted at three locations in Arizona (Maricopa, Marana, Safford) to evaluate 12 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 Marana location. Significant differences were found among the treatments used at the Maricopa and Safford locations.
    • Effect of Plant Nitrogen Status on Defoliation of Short-Season Upland Cotton

      Nelson, J. M.; Hart, Gary; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Field studies have been conducted over a four year period at the Maricopa Agricultural Center to determine the influence of nitrogen (N) fertility level on the effectiveness of chemical defoliants for short- season cotton production. Excessive N resulted in dense foliage and cotton that was difficult to defoliate. When plants were deficient in N from mid-season to termination, defoliants were very effective, but lint yields were reduced. The effectiveness of defoliants decreased as the petiole NO₃-N content increased. The optimum fertility program for short-season cotton is one that provides sufficient N during the season to produce maximum lint yields, but allows the crop to become deficient in N at the end of the season, prior to chemical defoliation.
    • 1991 Cotton Replant Decisions, Safford Agricultural Center

      Clark, Lee J.; Carpenter, Eddie W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Each planting season in the Safford valley there are fields that suffer stand reduction from adverse weather conditions. This study addresses some of the options and the economical effects from exercising these options on a field at the Safford Agricultural Center. References are made to work in California that have quantified the yield effect of stand reduction and chilling damage to cotton seedlings. This study shows that patience may pay better than rushing into the field to replant or rewater.
    • The Effects of PIX Application Timing on Lint Yield and Growth and Development Parameters

      Husman, S. H. .; Silvertooth, J. C.; Ramsey, C; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Two field studies were conducted in 1991 to further evaluate Upland cotton yield and development responses to PIX application timing as a function cotton growth stage. Treatments imposed in 1991 were intended to further clarify some response trends observed in previous field studies. Treatments in 1991 were all at the maximum label rate of 1.5 pt./acre with application timing the main variable. Timing was based on growth stage and heat unit accumulation since date of planting. The study in Waddell, Az. resulted in no significant yield differences across all treatments. In contrast, the study at the Maricopa Agricultural Center resulted in a statistically significant yield response by approximately 100 lbs. lint /acre for all FIX treatments compared to the untreated check plots. Plant growth and development measurements indicated the height: node ratio counts to be a good reflection of vegetative tendencies under field conditions in the two studies.
    • Pima Cotton Genetics

      Percy, R. G.; Turcotte, E. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      An investigation was conducted to determine the inheritance, allelism, and linkage associations of a spontaneous, male- sterile mutant found in plants of American Pima (Gossypium barbadense L.) cotton. Analyses of F₁, F₂, and BC populations of the mutant indicated that it was inherited as a single, recessive gene. T ests for allelism of the new gene with three previously described recessive male - sterility genes (ms₁, ms₂ and ms₃) were negative. Analyses of F₂ population segregation from crosses to 23 mutant marker stocks produced no evidence of linkage associations. We have proposed that the male sterility mutant be designated male-sterile-13 and be given the gene symbol ms₁₃. A conversion program to convert photoperiodic short-day accessions of a Gossypium barbadense germplasm collection to day neutrality continues.
    • Defoliation Research on Pima and Upland Cotton at the Marana Agricultural Center in 1991

      Nelson, J. M.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A field study was conducted at the Marana Agricultural Center to evaluate the effectiveness of ground rig applied defoliant treatments on Pima and Upland cotton under cool weather conditions. Defoliants were slow acting at this location, however, all chemical treatments tested resulted in good defoliation 14 days after application.
    • Effect of Plant Water Status on Defoliation and Yield of Upland Cotton for Short-Season Production

      Nelson, J. M.; Bartels, P. G.; Hart, G.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      A field study was conducted at the Maricopa Agricultural Center to determine the influence of plant water status at the time of defoliation on the effectiveness of defoliants and yield of short-season cotton. Irrigation termination dates of 14 and 26 August and 10 September were used to achieve different levels of plant water stress at the time defoliants were applied (19 September). Irrigation termination dates had no effect on seedcotton yield for cotton defoliated in September. As the period between the termination irrigation and the date of chemical defoliation was increased the effectiveness of defoliants was increased. CWSI and plant water potential measurements indicated that the irrigation termination dates resulted in large differences in plant water stress at defoliation time. There was a significant increase in the defoliation percentage as CWSI values increased (from 0.32 to 0.96) and water potential decreased (from -1.5 to -3.5 MPa). Short- season cotton (163 days) produced 4,396 lbs. seedcotton /A as compared to 5,299 lbs./A for a full-season crop (212 days).
    • Evaluation of Date of Planting and Irrigation Termination on the Yield of Upland and Pima Cotton

      Silvertooth, J. C.; Watson, T. F.; Malcuit, J. E.; Brown, P. W.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Five field experiments were conducted at three locations in 1991 in Arizona to evaluate the response of Upland and Pima cotton to dates of planting and dates of irrigation termination. Planting dates ranged from as early as 2 April in the Yuma Valley (150 ft. elevation) to 14 May at Marana (2,000 ft. elevation). Dates of irrigation termination ranged from 8 August in the Yuma Valley to 24 September at Maricopa. Planting date was commonly a significant effect in these experiments, particularly with Pima cotton. Irrigationtermination results over three locations and three seasons show increases of approximately 50 to 100 lbs. lint /acre by extending later irrigations.
    • Physiological Studies of Cotton Drought Tolerance

      McDaniel, R. G.; Dobrenz, A. K.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      We evaluated an array of progeny of interspecific cotton crosses in the field. Significant water stress was placed on the plants in mid-summer by withholding water supplied by drip irrigation during plant development earlier in the season. A number of physiological measurements were carried out on selected individual plants of this population during the several week period of imposed drought stress. Overall results confirm that a large degree of variation exists within the population for all traits measured. Initial carbon isotope discrimination measurements suggest this trait may prove useful in estimating transpiration efficiency of cotton genotypes.
    • Short Staple Variety Demonstration Summary, Maricopa Agricultural Center, 1989-1991

      Malcuit, J. E.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Short staple variety trials have been conducted for three years on the demonstration farm, at the Maricopa Agricultural Center. Twenty varieties, received from various seed companies, were entered into the test in 1989, 19 varieties in 1990, and 10 varieties in 1991. Yields ranged from 3353 to 4679 lbs. seedcotton/acre in 1989, 829 to 1428 lbs. lint/acre in 1990 and 1099 to 1246 lbs. lint/acre in 1991. Results form the statistical analysis showed significant differences among varieties for all three years. Differences among varieties in 1989 showed no clear trends with respect to maturity types. In 1990, those varieties that were medium to early season maturity types yielded higher than full season maturity types. The results in 1991 showed medium maturity types yielding in the highest ranking of the test without exception, while the performance of the full season maturity types was mixed. An additional test with narrow row spacing (30 inches) was included in 1991 with 5 varieties. Yields ranged from 947 to 1117 lbs. lint/acre. No significant differences were detected among varieties.
    • Efficacy of the Insect Growth Regulator, Buprofezin and the Insecticide, Amitral against the Sweetpotato Whitefly on Cotton at Maricopa, AZ, 1991

      Akey, D. H.; Chu, C. C.; Henneberry, T. J.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Reduction of populations of the B strain (poinsettia) of sweetpotato whitefly (SPWF), Bemisia tabaci Gennadius, resulted from applications of buprofezin or amitraz to cotton in central Arizona (Maricopa, AZ). Control was fair to good control for this insect. However, yields of seed cotton in treated plots were not increased significantly compared to untreated plots, following three applications of these insecticides during the season. Similar results on percentage sugar on lint and lint stickiness from honeydew of SPWF in both treated and untreated plots were obtained.
    • Short Staple Variety Trials, Greenlee County, 1991

      Clark, Lee J.; Schneider, Mike; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Fourteen acala and four delta varieties were tested in two separate field trials in Greenlee county in 1991. Yields at both sites were about 1000 pounds per acre (seed cotton yields) than the 1990 yields. Cool weather and wet grounds delayed planting one to two weeks compared with 1990. The highest yielding varieties, both acala and delta type, produced around 2300 pounds per acre of seed cotton. An experimental New Mexico acala, B510 and Stoneville 506 were the top varieties.
    • Response of Nectaried and Nectariless Pima Cotton to Pink Bollworm

      Wilson, F. D.; Percy, R. G.; Turcotte, E. L.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Four Pima cotton entries were grown in large plots at MAC, not treated with insecticide, to determine their response to attack of pink bollworm. P62, an early -maturing germplasm line, sustained significantly less seed damage caused by pink bollworm than did 'Pima S-6', Pima S-6 nectariless, and P62 nectariless. The nectariless trait did not reduce seed damage significantly.
    • Short Staple Variety Demonstration, Pinal County, 1988-1991

      Malcuit, J. E.; Stedman, S.; Silvertooth, J. C.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Short staple variety trials were conducted for four years at Prechel Farms near Coolidge Az. Six varieties were included in 1988, twelve in 1989, eight in 1990, and eight in 1991. Results from the statistical analysis showed significant differences among varieties in each of the four tests. Lint yields ranged from 908 to 1313 lbs. lint acre⁻¹ in 1988, 2844 to 4827 lbs. seedcotton acre⁻¹ in 1989, 695 to 1059 lbs. lint acre⁻¹ in 1990, and 1065 to 1286 lbs. lint acre⁻¹ in 1991. Those varieties that were medium to short- season maturity types yielded higher than long season maturity types in the 1988 and 1990 seasons. The reverse was true in the 1989 season and results were mixed in 1991.
    • Insecticidial Control of the Sweet Potato Whitefly in Cototn

      Watson, T. F.; Silvertooth, Jeff (College of Agriculture, University of Arizona (Tucson, AZ), 1992-02)
      Four field experiments were conducted to evaluate efficacy of a number of registered or experimental insecticides against the sweet potato white fly. Several materials gave encouraging results under unusually high population densities. Among the more effective treatments in one or more tests were: Capture, Danitol, NTN 33893, pyriproxyfen and SN 85292, and combinations of Capture +endosulfan, Capture +Ovasyn and Danitol +Orthene.