• Application and Timing of Insecticides for Aphid Management in Head Lettuce

      Palumbo, John; Mullis, Clayton Jr.; Reyez, Francisco; Amaya, Andreas; Ledesma, Luis; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      The timing and application methods of new insecticide chemistries for aphid control were compared to imidacloprid in several studies in 1998 and 1999. Foliar applications of Fulllfill, Aphistar, Actara and Acetamiprid appear to provide an alternative method of controlling aphids on lettuce comparable to prophylactic applications of Admire. Timing applications as aphids began to colonize was critical for preventing head contamination at harvest. In addition, at planting and side dress soil applications of Platinum provided aphid control comparable to Admire. Residual activity of the new foliar alternatives appeared to differ depending on spray timing relative to aphid density and plant stage. These studies suggest that more than one application of the foliar products will be necessary to adequately suppress aphid contamination in heads. Evaluations of thiamethoxam suggest that it is more mobile in the soil than Admire and may be a candidate for side dress applications for aphid management.
    • Assessment of Fungicides Performance for Control of Powdery Mildew of Lettuce in 1999

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Erysiphe cichoracearum is the fungus that causes powdery mildew of lettuce, a disease favored by warm and dry weather conditions. Several potential new fungicides were evaluated for control of this disease in 1999. Untreated lettuce plants were heavily infected with powdery mildew, whereas the disease was very light to virtually nonexistent in plots treated with Sovran, BAS 500, Rally and DPX-MU752. Higher levels of powdery mildew, still significantly less than that observed on untreated plants, were recorded in plots treated with the standard materials Microthiol Special and Trilogy in addition to several other compounds. The possible availability of one or more of these chemistries under development could help in efforts to control powdery mildew of lettuce and to establish and maintain a fungicide resistance management program for plant disease control products of importance for this crop.
    • Canarygrass Control in Wheat

      Tickes, Barry; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
    • Comparison of New Fungicides for Management of Downy Mildew of Broccoli in 1999

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Downy mildew of broccoli, cauliflower and cabbage is caused by the fungus Peronospora parasitica. Cool moist environmental conditions favor the development of downy mildew on these crops. Several potential new fungicides were evaluated for control of this disease on broccoli in 1999. The final severity of downy mildew in this trial was moderately high. Significant reduction in disease severity compared to nontreated plants was achieved by application of standard compounds such as Aliette, Ridomil Gold+maneb, maneb and Trilogy as well as nonregistered chemistries including Acrobat, Actigard, Curzate, Flint, Quadris, Serenade, Sovran, BAS 500, DPX-KP481 and RH-7281. The future registration and subsequent availability of one or more of these new chemistries for broccoli and related crops could enhance the overall level of disease control as well as help minimize the risk of development of resistance to fungicides used to manage downy mildew.
    • Cross Commodity Management of Whiteflies and Chemical Efficacy in Arizona

      Palumbo, John; Ellsworth, Peter; Umeda, Kai; Dennehy, Tim; Arbogast, Mike; Evans, Lin; Hannan, Todd; Minch, Ed; Nichols, Bob; Byrne, David N.; et al. (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      The Western Growers Association and Arizona Cotton Growers Association worked cooperatively with a group of University of Arizona scientists, Arizona Department of Agriculture officials and regional pest control advisors to develop general guidelines for managing whiteflies and specific recommendations for Applaud and Admire use. This was achieved by identifying differences in crop production, insecticide use, and whitefly population dynamics on key host crops within three distinct growing regions in Arizona. Data was compiled that when graphically illustrated identified important, multidimensional interactions within cropping systems. Based on the patterns resulting from our analysis, initial recommendations have been formulated to harmonize chemical use across commodities by restricting Applaud use to only once per crop season in use windows, with additional guidelines for reducing the possibility of exposing successive whitefly generations to the same mode of action. The diversification and limitation of Admire and other active ingredients, and the employment of cultural practices are also be considered. Should this model of cooperation be successful, valuable and scarce modes of action may also be shared in the future within diverse, integrated use systems.
    • Defoliant Effect on Melons

      Umeda, Kai; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Sodium chlorate exhibited the fastest developing crop phytotoxicity symptoms within 3 days after treatment (DAT). Within three days of application, significant crop injury at 40 and 80% was observed on cantaloupes for sodium chlorate applied at 1.0 and 4.0 lb AI/A, respectively. Thidiazuron/diuron (Ginstar7) caused injury that was slightly slower to develop and the crop declined severely during the next 10 days. Ginstar at 8.0 or 12.0 oz product/A initially caused 20% crop injury. Thidiazuron (Dropp7) caused the least injury on cantaloupes and injury reached unacceptable levels at 1 WAT. Dropp at 0.1 and 0.4 lb AI/A initially showed less than 10% crop injury. Dropp at the rates tested caused minimal defoliation.
    • Development and Consumption Rates for Lepidopterous Larve as Influenced by Host-Plant and Temperature

      Palumbo, J. C.; Reyes, F.; Amaya, A.; Ledesma, L.; Cary, L.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Several laboratory studies were conducted to examine the relationships between larval developmental and foliage consumption. Neonate lepidopterous larvae were placed in controlled environment growth chambers to measure the time required to complete larval growth, and comparative foliage consumption at constant temperatures. Differences in developmental times and degree day estimates between beet armyworm and cabbage looper varied significantly with temperatures and host plant. In general, cabbage looper feeding on lettuce completed larval development at a more rapid rate and consumed more foliage than any other species-host combination. In one study, the time required to complete larval development between CL and BAW varied less than one day, but the difference in foliage consumed between the two hosts varied almost 40%. Results from these studies may provide information important for understanding the damage potential of lepidopterous larvae and optimizing use patterns for new compounds that will be integrated into management programs for leafy vegetables.
    • Diamondback Moth Control in Spring Cabbage Study

      Umeda, K.; Strickland, B.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Spinosad (Success7), chlorfenapyr (Alert7), DPX-MP062 (DuPont), thiodicarb (Larvin7), and cryolite (Kryocide7) progressively reduced the total number of Plutella xylostella (diamondback moth, DBM) following each of three applications. Success treated cabbage had the fewest number of small-sized DBM larvae after the first application and maintained very low numbers following subsequent applications. Relative performance of the insecticides based on efficacy indicated by a seasonal average of total DBM larvae showed that Success was highly effective followed by methomyl (Lannate) and Larvin. Emamectin-benzoate (Proclaim7), Alert, and DPX-MP062 performed comparably and tebufenozide (Confirm7) and Kryocide were less effective.
    • Early Postemergence Herbicide Weed Control in Onions

      Umeda, K.; MacNeil, D.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Onions treated with bromoxynil (Buctril7) or oxyfluorfen (Goal7) at the time when the first true leaf was emerging were not injured. No significant onion crop stand reduction occurred from any of the postemergence (POST) treatments. Onion height was not affected by any of the POST treatments through the season. A single application of Goal or Buctril offered up to 7 WAT of very good weed control with excellent crop safety. Onions treated at the typical 2-leaf stage of growth with Buctril or Goal exhibited no significant crop injury. Delayed and reduced control of knotweed (Polygonum aviculare) could have contributed to the decreased onion yield in the herbicide treated onions compared to the handweeded check. Onions in the untreated check were significantly reduced compared to Goal treated onions or the handweeded check.
    • The Effect of Irrigation Practices on the Performance of Lettuce Herbicides

      Tickes, Barry; Byrne, David N.; Baciewicz, Patti; University of Arizona Cooperative Extension (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      The herbicides used in lettuce have changed little in more than 30 years. Poast was registered for grass control in the 1980's although preemergent applications of Kerb, Balan and Prefar have been the principal herbicides used in lettuce production since the mid 1960's. Balan was changed from a 1.5 lb./gal. Emulsifiable concentrate to a 60% dry flowable formulation in the mid 80's, Kerb has always been a 50% wettable powder and Prefar is still a 4 lb./gal. emulsifiable concentrate. Growers are constantly changing cultural practices to improve production or to become more efficient. The change in one cultural practice can, and often does, effect other cultural practices. The use of sprinklers to establish lettuce has become increasingly widespread in the Yuma area over the past 20 years. Kerb and Prefar can be mechanically incorporated into shaped beds although both are commonly incorporated with irrigation water. The change in irrigation practices during stand establishment from furrow irrigation to sprinklers has effected the performance of both Kerb and Prefar. Balan is normally disced into the soil prior to bed formation and is not as effected by irrigation practices during stand establishment. Four tests are presented in this paper that help explain the effect of irrigation practices on the performance of Kerb and Prefar.
    • Effect of Onion Bed Shape on Accumulation of Soluble Salts and Sodium

      Knowles, Tim C.; Poole, Charles; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      An experiment was conducted to examine the effectiveness of knifing a vshaped notch into the center of raised onion beds for reducing soluble salt accumulation in the seed rows. Sodium salts accumulated within an 18 inch wide band in the top six inches of the knifed raised bed profile. Sodium salts accumulated primarily within a narrow six inch wide band, and to a somewhat lesser extent, within an 18 inch wide band in the top six inches of the conventional raised bed profile. Total soluble salts accumulated primarily within a six inch wide band in the top six inches of the knifed and conventional onion raised bed profiles.
    • Efficacy of Insecticides to Diamondback Moth in Cabbage in Yuma County

      Kerns, David L.; Tellez, Tony; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Commercial and experimental insecticides were evaluated for their ability to control diamondback moth (DBM) on green cabbage in Yuma, AZ. At early to mid-heading, all the insecticides evaluated appeared to offer similar control. However, on large, full sized cabbage, Asana, Alert, Lannate, Success and S-1812 offered the best DBM control, while Lorsban, Proclaim and Intrepid appeared weak. Unlike other areas of the U.S., DBM in Yuma still appears to be highly sensitive to a wide range of insecticide chemistries.
    • Evaluation of Foliar Insecticides for Whiteflies in Cantaloupes

      Umeda, Kai; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      A single application of buprofezin (Applaud7) at 0.38 lb AI/A had the fewest number of adult whiteflies (WF) on rating dates at 13, 21, and 27 days after treatment (DAT). The number of immature WF at 21 DAT of a single Applaud application ranged from 0.8 to 5.2 nymphs/leaf, significantly less than the untreated. Applaud treatments were effective in minimizing the immatures for 21 DAT of a single application and then numbers began to increase before 27 DAT. Applaud plus two subsequent weekly applications of bifenthrin (Capture7) plus endosulfan (Thiodan7, Phaser7) was almost similar to single applications of Applaud alone and adult numbers were also low. Weekly applications of the pyrethroids plus endosulfan reduced the adult WF relative to the untreated at 1 week after treatment (WAT). At 2 WAT of the third application, fenpropathrin (Danitol7) and Capture continued to show reduced numbers of adults and esfenvalerate (Asana7) was similar to the untreated. Danitol treatments had numerically fewer adults than Capture which was lower than Asana. The lowest adult and immature WF populations were observed season-long in the CGA-293343 (Novartis) treated cantaloupes. Both rates, 0.067 and 0.09 lb AI/A performed similarly and numerically slightly fewer nymphs were observed for the higher rate. CGA-293343 plus CGA-215944 (pymetrozine, Fulfill7) performed similar to the two rates of CGA-293343 alone.
    • Evaluation of Herbicides for Cantaloupe Weed Control

      Umeda, Kai; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      At 4 weeks after treatment (WAT), all preemergence (PREE) treatments were completely safe on cantaloupes. At 1 WAT of postemergence (POST) applications, marginally acceptable melon injury (11 to 19%) was observed. At 6 WAT, crop injury increased significantly for both halosulfuron and bentazon. Halosulfuron (POST) following bensulide (PREE) caused minimal crop injury. The pigweeds were marginally controlled when POST treatments followed PREE herbicides. Tumble pigweed (Amaranthus albus) was more difficult to control than prostrate pigweed (A. blitoides). Halosulfuron gave good control of nutsedge (Cyperus rotundus) at 6 WAT.
    • Evaluation of Knack for Aphid Control in Green Leaf Lettuce

      Kerns, David L.; Tellez, Tony; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Knack was evaluated for its potential for regulating aphid populations in green leaf lettuce. However, Knack did not appear to be a viable control option, and probably did not work due to an inability to deliver the material where the aphids were on the underside of the lower leaves. A soil injection treatment of Admire at planting, and a foliar standard of Warrior + Endosulfan applied at the initiation of aphid colonization and again 14 later, were highly effective treatments.
    • Evaluation of New Fungicides for Management of Sclerotinia Leaf Drop of Lettuce in 1999

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      In Arizona, Sclerotinia leaf drop of lettuce is caused by two different species of fungi, Sclerotinia minor and S. sclerotiorum. Relatively cool and moist environmental conditions favor this disease. Some new fungicides in development were evaluated for control of leaf drop on lettuce during the winter vegetable growing season of 1998-99. Sclerotia of each pathogen were applied to plots after thinning and just before the first of two applications of test compounds. The final severity of leaf drop in these trials was moderately high. Significant reduction in the final count of dead lettuce plants compared to nontreated plots was usually achieved by application of the standard compounds Ronilan and Rovral as well as an appropriate rate of the experimental compounds Elevate, Medallion or Serenade. Medallion and Elevate provided equivalent disease control to that of the current standard materials with 0.178 and 0.5 lb active ingredient (a.i.) per acre, respectively, compared to the current 1.0 lb a.i. per acre required with the standard compounds. Continued demonstration of efficacy by Serenade may provide the opportunity to utilize a biological control product to reduce the incidence of Sclerotinia leaf drop of lettuce.
    • Evaluation of New Insecticides for Aphid Control in Green Leaf Lettuce

      Kerns, David L.; Tellez, Tony; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      New soil injected and foliar insecticides were evaluated for their efficacy towards potato aphids in green leaf lettuce. The soil injected insecticides, Platinum and V10066, both appear to be viable alternatives to Admire, providing effective aphid control through harvest or ca. 90 days post-planting. Two foliar applications of Acetamiprid or Aphistar timed ca. 14 days apart beginning at the onset of aphid colonization provided superior aphid control over Provado or Fullfill, and control similar to that of the soil injected insecticides.
    • Evaluation of Preemergence Herbicides for Early Season Onion Weed Control

      Knowles, Tim C.; Poole, Charles; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Two experiments were conducted to determine the efficacy and safety of soil applied broadcast preemergent herbicides including Nortron, Prowl, Prefar, and Prefar + Prowl combinations applied at planting to fall seeded dry bulb onions. Crop stand reductions ranging from 10 to 33 percent resulted from Prowl 3.3EC use rates of 1.2 and 2.4 pt/acre. Prowl 3.3EC applied at 0.6 pt/acre, Prefar 4E applied at 4 and 6 qt/acre, Nortron 4SC applied at 2 pt/acre, and the combination of 0.6 pt Prowl 3.3 EC plus Prefar 4E were safe on fall seeded onions. Prefar plus Prowl combinations also provided winter weed control equal to or better than the standard 14 lb/acre Dacthal 75WP.
    • Fertigation Frequency Effects on Yield and Quality of Subsurface Drip-Irrigated Broccoli

      Thompson, Thomas L.; White, Scott A.; Walworth, James; Sower, Greg; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Subsurface drip irrigated broccoli received experimental combinations of N rate (176 and 268 lb N/ac, and fertigation frequency (daily, weekly, bi-weekly, monthly) at the Maricopa Agricultural Center during winter 1998-99. Marketable broccoli yields were increased slightly with N applications of 268 lb/acre compared to 176 lb/acre. However, neither marketable yield, head diameter, nor petiole nitrate concentrations were significantly affected by fertigation frequency. Nitrogen fertigation frequency does not seem to be a critical management variable for subsurface drip irrigated broccoli grown on medium-textured soils in Arizona.
    • Field Performance of Admire Against Silverleaf Whitefly on Commercial Iceberg Lettuce, 1993-1998

      Palumbo, John C.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 1999-10)
      Whitefly populations in the Yuma area have been reduced to levels that growers can cost-effectively manage. Data from our studies suggest that these declines in pest populations are largely attributed to the use of Admire 2F (imidacloprid) soil treatments. Relative to the outbreaks in 1993-1994, whitefly populations during the past four growing seasons have remained at sub-economic levels on lettuce crops throughout the growing areas in Yuma This chemical has provided excellent control of whiteflies on fall lettuce, and aphids on spring lettuce. After 6 years of evaluation in commercial fields, the product appears to remain highly efficacious, maintaining good residual activity. Studies in 1998 on fall broccoli and melons crops further support this conclusion. Factors responsible for this sustained efficacy of Admire are discussed.