• Effect of Sunstainable Versus Conventional Fertilization Practices on Populations of Pythium and Fusarium on Roots of Lettuce in 1990 Field Test

      Matheron, M.; McGrady, J.; Butler, M.; Rethwisch, M.; Matejka, J.; Tilt, P.; Oebker, Norman F.; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1991-05)
      This report focuses upon our efforts to evaluate the effect of sustainable versus conventional fertilization practices on subsequent populations of soil-borne pathogens on lettuce roots. The different fertilization treatments included conventional fertilizer, composted cow manure, and a biological soil conditioner. Near plant maturity, lettuce roots were collected from the field and the populations of Pythium and Fusarium were determined. The lowest population of both of these pathogens was found in the plots fertilized with composted cow manure, while the highest levels of Pythium and Fusarium were detected in the plots treated with conventional fertilizer. Further field studies are planned to confirm these initial findings. Of the two pathogens assayed, Pythium is of greatest concern because of its ability to destroy roots and reduce plant growth and vigor. Species of Fusarium are commonly found in soil and on plant roots and usually do not cause damage to plants unless the plants are under stress.
    • Effect of Treatment of Lettuce Seeds with Fusicoccin and Other Growth Regulators on Seedling Emergence at High Temperature

      Nelson, J. M.; Sharples, C. C.; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1986-04)
      Lettuce stand problems in desert production areas are, in many instances, related to high seedbed temperatures and the use of seed coatings. We evaluated the use of fusicoccin and other growth regulators to improve the performance of naked and coated lettuce seeds at high temperature. Treatment of both naked and coated seeds with fusicoccin markedly increased the rate and total emergence of seedlings incubated at 35 °C for 10 hours alternating with 23 °C for 14 hours.
    • Effectiveness of Oils in Water for Leafminer Control in Fall Head Lettuce

      Rethwisch, Michael D.; Hood, Larry; Meadows, Mike; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Effects of Lettuce Insecticides Applied at Planting

      Rethwisch, Michael D.; Meadows, Michael; Hagerman, Shari; Thiessen, James; McGrady, John; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Efficacy and Temporal Mortality of Selective Insecticides on Beet Armyworm Larvae in Lettuce

      Palumbo, J. C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
    • Efficacy of Biorational Insecticides to Beet Armyworm and Cabbage Looper on Iceberg Lettuce

      Kerns, David L.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Four tests were conducted evaluating biorational insecticides for control of beet armyworm (BAW) and cabbage looper (CL) on iceberg lettuce. Treatment means for BAW were difficult to separate due to low population densities. The new formulation of Javelin appeared to be the most efficacious Bt overall. However, when Bts were compared on a equal cost/A basis, there were no significant derences among products for CL control. All Bts were comparable to Lannate for CL control. The neem oil extract Align, provided adequate BAW and CL control, and its efficacy at low rates seemed to be slightly enhanced by the addition of Sunspray Ultrafine Oil. Larvin at lower than label recommended rates gave good BAW and CL control as did Javelin. The tank-mix of these two products did not enhance worm control over that of the products used alone. Mustang gave good control of CL but appeared to be slightly weak against BAW.
    • Efficacy of Insecticides to Green Peach Aphid on Iceberg Lettuce

      Kerns, David L.; Palumbo, John C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Three tests were conducted evaluating foliar and soil applied aphicides for efficacy to green peach aphid infesting iceberg lettuce. Aphid population densites were low in all three studies and differences among treatments were difficult to discern. At low aphid populations we could not detect whether or not soil applications of Admire enhanced or inhibited the activity of subsequent foliar applications of other aphicides. Although when used alone, some products did offer statistically significant aphid control. However, in a commercial setting these differences would probably not be significant. At low aphid populations none of the pyrethroid tank mixes evaluated gave significantly better aphid control than the products used alone. All of the experimental aphicides evaluated appeared to have some degree of efficacy to green peach aphid.
    • Efficacy of Pyrethroid Insecticides for Cabbage Looper Control in Head Lettuce, 1997

      Kerns, David L.; Tellez, Tony; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1999-02)
      Mustang 1.5EW, Ammo 2.5EC, Pounce 3,2EC, Scout X-TRA, and three formulations of Karate were compared for efficacy to cabbage loopers infesting head lettuce in Yuma, AZ Karate and Pounce provided the most consistent cabbage looper control followed by Mustang and Scout X-TRA. Ammo appeared slightly inferior to the other pyrethroids tested. There did not appear to be any obvious differences in the efficacy of the three Karate formulations.
    • Evaluation of Admire Soil Treatments on Colonization of Green Peach Aphid and Marketability of Lettuce

      Palumbo, John; Kerns, David; Hannan, Todd; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1995-08)
      Admire (imidacloprid), applied as a soil treatment, protected lettuce plants from developing infestations of green peach aphid, Myzus persicae (Sulzer), for 60-100 d after planting based on two small plot and two commercial field trials. Admire applied 7.6 cm sub-seed furrow provided longer and more consistent protection from green peach aphid than treatments applied to the soil surface, as a side-dress, or 15.2 cm sub-seed furrow. Surface band applications of Admire provided inconsistent control probably because of inadequate hydrological incorporation into the soil. In small plot trials, effective control of aphids by Admire applied 7.6 cm sub seed furrow resulted in greater than 90.0% marketable heads while the untreated plots contained 20.0% marketable heads. When used in a commercial setting, Admire applied 7.6 cm sub-seed furrow on leaf lettuce prevented aphid colonization (<3 aphids per plant) for approximately 100 d after planting, while the untreated and commercial standard treated areas contained 30.7 and 26.8 aphids per plant respectively at 100 d after planting. In addition, marketability of lettuce was greater in Admire treated plots. As a sub-seed furrow treatment, Admire provides a more suitable approach to aphid control than is currently available with foliar insecticides.
    • Evaluation of Agri-Mek with Various Oils and Adjuvents for Control of Leafminers in Spring Head Lettuce

      Rethwisch, Michael D.; Meadows, Michael; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Evaluation of Biological Insecticides for Control of Beet Armyworm in Lettuce

      Palumbo, John C.; Butler, Marvin D.; Mullis, Clayton H. Jr.; Oebker, Norman F.; Bantlin, Marguerite (College of Agriculture, University of Arizona (Tucson, AZ), 1991-05)
      A field study was conducted at Yuma in 1990 to examine the efficacy of several biological insecticide formulations on beet armyworm in seedling lettuce. After a single application at thinning, none of the insecticides adequately reduced larval populations below damaging levels. Reductions in plant stand by larvalfeeding were significantly lower in plots treated with Lannate, Javelin, Biobit and Dipel. Lettuce seedling densities were reduced greaterthan 80% in untreated plots.
    • Evaluation of Conventional and Experimental Insecticides for Control of Western Flower Thrips in Head Lettuce

      Palumbo, John; Mullis, Clayton Jr.; Reyes, Francisco; Amaya, Andreas; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Studies were conducted in small plot field trials to evaluate the efficacy of several experimental and conventional insecticide chemistries against western flower thrips in head lettuce. Results from two trials using new experimental compounds showed that several insecticides have potential for management of thrips populations. All of the products appear to be good candidates for thrips control and had efficacy against adults and nymphs. Success and Fipronil consistently provided comparable control to the standard Lannate/Ammo. In the trial evaluating conventional compounds, Orthene/Mustang and Lannate/Ammo combinations provided the best control of both adult and nymphs. Plant size and temperature may be important factors contributing to the efficacy of these products.
    • Evaluation of Foliar Applied Nutritional Mixes on Crisphead Lettuce for Yield, Quality and Incidence of Tipburn

      Wilcox, M.; Sanchez, C. A.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1994-09)
    • Evaluation of Foliar Insecticide Approaches for Aphid Management in Head Lettuce

      Palumbo, John; Mullis, Clayton Jr.; Reyes, Francisco; Amaya, Andreas; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Provado insecticide (imidacloprid) was compared to Admire and other standard insecticides for management of aphids in head lettuce in Yuma 1995 and 1996. Foliar applications of Provado appear to provide an alternative method of controlling aphids on lettuce comparable to prophylactic applications of Admire. The prevention of aphid colonization in lettuce heads with Provado may depend greatly on the timing and frequency of applications before harvest occurs. These studies and other studies on spinach suggest that more than one application of Provado will be necessary to adequately suppress aphid contamination in heads. The label suggests that applications be timed 5-7 apart. Our data tends to support this recommendation. Furthermore, timing applications should be based on days to harvest, level of aphid colonization and duration of aphid migration.
    • Evaluation of Head Lettuce Varieties for Liriomyza trifolii Leafminer Populations

      Rethwisch, Michael D.; Butler, Marvin D.; Meadows, Mike; Oebker, Norman F.; Kingdon, Lorraine B. (College of Agriculture, University of Arizona (Tucson, AZ), 1989-05)
    • Evaluation of New Fungicides for Management of Downy and Powdery Mildew of Lettuce in 1998

      Matheron, Michael E.; Porchas, Martin; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1999-02)
      Bremia lactucae and Erysiphe cichoracearum, respectively, cause downy and powdery mildew of lettuce. Cool moist environmental conditions favor the development of downy mildew, whereas warm and dry weather is conducive for powdery mildew. Several potential new fungicides were evaluated for control of these diseases of lettuce in 1998. The final severity of downy mildew in this trial was low. In addition to the standard compounds maneb, Aliette and Trilogy, several fungicides currently in development significantly reduced the severity of downy mildew compared to nontreated plants. These chemistries included Acrobat, RH -7281, an Unknown, Actigard, EF1295, Curzate, Quadris, BAS 500, QST 153, BAS 505 and BAS 490. Untreated lettuce plants were heavily infected with powdery mildew. In addition to the standard materials Microthiol Special and Trilogy, powdery mildew was significantly reduced on plants treated with BAS 490, BAS 505, EF1295, BAS 500 and Quadris. The possible availability of one or more of these chemistries under development for lettuce could help in efforts to develop and maintain a fungicide resistance management program for plant medicines of importance for this crop.
    • Evaluation of Soil Amendments for Lettuce Production in the Desert

      Sanchez, C. A.; Silvertooth, J. C.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Two field studies were conducted during the 1993-1994 season to evaluate the response of lettuce to soil applied amendments. Treatments included gypsum, polymaleic acid (Spersal), and two acid products (N-phuric and Phos-phuric). Gypsum rates (0, 2240, and 4480 kg /ha) were the main plots and other soil amendments were subplot randomized within the mainplots. Overall, gypsum reduced early growth and vigor of lettuce. Gypsum had no effects on marketable yield and quality parameters in experiment 1, but the highest gypsum rate (4448 kg /ha) decreased marketable yield in experiment 2. There were no differences in plant stands due to subplot treatments. However, there were differences in earlygrowth and vigor. In experiment 1, both "N-phuric" and "Phos-phuric" increased early lettuce growth compared to the control. In experiment 2, Phos-phuric was superior to N-phuric. In experiment 1, the benefits of early growth and vigor to the "N-phuric" and "Phos-phuric" carried to harvest where marketable yield and quality were significantly increased. Spersal did not significantly effect yield and quality of lettuce in either experiment.
    • Evaluation of Two Electrostatic Sprayers Compared with Conventional Application Methods for Control of Insects in Spring Head Lettuce

      Rethwisch, Michael D.; Coates, Wayne; Main, Greg; McDaniel, Charles W.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1992-12)
    • Field Emergence and Seedling Growth of Lettuce as Affected by Pre-Plant/Pre-Emergent Herbicides

      Sill, David W.; Tickes, Barry; Carey, Lisa A.; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Pre plant and pre- emergence herbicides are commonly used in lettuce production. We investigated possible effects the herbicides benefin (Balan), pronamide (Kerb) and bensulfide (Prefar) had on emergence and seedling growth of several iceberg lettuce varieties that had been primed and pelleted by seed enhancement companies The herbicide Prefar and a mixture of Balan + Prefar had the greatest impact on dry weight regardless of variety, while seedlings grown on Kerby plots were not significantly different than seedlings from untreated plots. Dry weight accumulation and field emergence were influenced significantly by pellet types and priming methods.
    • Field Evaluation of Head Lettuce Cultivars for Susceptibility to Sclerotinia Leaf Drop in 1997

      Wilcox, Mark; Matheron, Michael; Oebker, Norman F. (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Leaf drop of lettuce is caused by the plant pathogenic fungi Sclerotinia minor and S. sclerotiorum. Cool and moist environmental conditions favor disease development. Sixteen diffirent cultivars of head lettuce were evaluated in the field for susceptibility to Sclerotinia leaf drop in plots inoculated with sclerotia of Sclerotinia minor or S. sclerotiorum. Significant differences were detected among the tested cultivars in the amount of lettuce plants killed by Sclerotinia minor. On the other hand, there were no significant differences among tested cultivars in the number of plants destroyed by Sclerotinia sclerotiorum