• Field Evaluation of Crisp-head Lettuce Varieties Grown in Southwest Low Desert Soils

      Zerkoune, Mohammed A.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Crisp-head lettuce plays an important role in Yuma’s economy. An estimated 51000 acres are cropped to large number of varieties each year with planting season that spreads from late August to March. Three demonstration sites and three planting dates were selected to compare new and existing varieties of head lettuce on growers’ fields using standard farming practices. Selected growth parameters were evaluated throughout the growing season. Results indicate that varieties tested at JV Farms in Welton and at Yuma Agricultural Center (YAC) are expected to do well if grown under similar conditions and planting time. Some varieties tested during the second planting slot on Doug Melon Farm experienced some incidence of diseases. All three planting sites showed a significant head weight difference and two out of three planting sites showed a significant head diameter difference.
    • Comparative Effect of Five Fungicides on the Development of Root and Stem Rot and Survival of Chile Pepper Plants Grown in Field Soil Naturally Infested with Phytophthora capsici

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Five different fungicides, including azoxystrobin, dimethomorph, fluazinam, fosetyl-Al, and mefenozem (metalaxyl), were evaluated for their ability to inhibit the development of root and crown rot and increase the survival of chile pepper plants grown in soil naturally infested with Phytophthora capsici. For chile pepper plants grown in field soil naturally infested with P. capsici and subjected to a 48 h flood period every 2 weeks, growth and survival of plants receiving one treatment of dimethomorph at 100 μg/ml or fluazinam at 1,000 μg/ml were significantly greater than that for plants treated once with azoxystrobin at 1,000 μg/ml or fosetyl-Al at 3,000 μg/ml. For each tested fungicide, values for duration of plant survival and shoot and root fresh weight usually were numerically larger but not significantly different for chile peppers receiving water as needed compared to those flooded for 48 h every 2 weeks. The potential and relative value of azoxystrobin, dimethomorph, fosetyl-Al, and fluazinam as chemical management tools for Phytophthora root and stem rot on chile pepper, in addition to mefenozem (metalaxyl), has been demonstrated.
    • Aphid Control in Cabbage Study

      Umeda, K.; MacNeil, D.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Aphistar provided the quickest reduction of the aphids after one application and continued residual control for up to 14 DAT-2. Following a second application and reduction of aphids, Pirimor, Provado, Fulfill, Actara, and Metasystox-R provided a varied degree of residual control of aphids between 5 and 14 DAT-2. A comparison of Fulfill rates indicated that the two rates were equally effective at 5 DAT-2 but the lower rate did not offer as long residual control compared to the higher rate. Endosulfan was moderately effective and did not provide acceptable control after 1 week.
    • Evaluation of Foliar Insecticides for Whitefly Control in Cantaloupes

      Umeda, K.; MacNeil, D.; Roberts, D.; Lund, N.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      The pyrethroid insecticides esfenvalerate (Asana®), bifenthrin (Capture®), or fenpropathrin (Danitol®) combined with endosulfan effectively reduced whitefly (WF, Bemisia argentifolii) counts at 1 week after treatment (WAT) following each of five applications. Asana, Capture, or Danitol combined with endosulfan effectively reduced WF counts at 1 WAT following each of five applications. Danitol treated melons exhibited fewer adult WF compared to Asana or Capture at most of the rating dates at 6 days after treatment (DAT) of each of the applications and also at 11 DAT of the last application. A single application of buprofezin (Applaud®) treatments or pymetrozine (Fulfill®) effectively reduced WF nymphs for 18 to 24 DAT and adults were reduced for 18 DAT. Fulfill exhibited a rate response where the higher rate reduced WF counts more than the lower rate.
    • Alternative IPM Programs for Management of Lepidopterous Larvae in Fall Lettuce

      Palumbo, John; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      For a third year, a large block experiment was conducted at the Yuma Ag Center to compare the field performance of several lettuce IPM programs for control of lepidopterous larvae. Conventional, Reduced -risk , Bio-based and Modified IPM spray regimes were applied to control beet armyworm, cabbage looper and Heliothis species throughout the fall growing season. Differences in populations of total larvae among the treatments, relative to insecticide treatments and timing of application were observed at various times during the season. In general, the Conventional, Reduced -risk and Modified IPM approaches provided the most consistent control of lepidopterous larvae following each application. Harvest data showed that the spray regimes had a significant influence of head lettuce yield or quality. Maturity and quality were significantly reduced in the untreated control. An economic analysis shows that net returns varied widely among the management programs at different market prices. In conclusion, this study provides a strong data base to support the need for the development of experimental and biorational insecticide products as alternatives to conventional management programs in desert lettuce production. In addition, it demonstrates the dependance of IPM programs on a broad range of plant protection chemicals and control tactics.
    • Baseline Susceptibility of Cabbage Looper to Insecticides

      Kerns, David L.; Tellez, Tony; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Populations of cabbage looper were collected during 1998 from 12 geographical location in the United States, and were assessed for susceptibility to six new insecticides: Alert, Avaunt, Confirm, Intrepid, Proclaim, and Success, and to a standard insecticide, Pounce. There was no detectable evidence indicating insecticide resistance to any of the new insecticides. However, variability in response to Confirm, Proclaim, and Success warrants close resistance monitoring. Cabbage looper response to Pounce was extremely variable, and there was strong evidence for the occurrence of resistance. Populations from Jackson, MS, Sunderland, MA, and Whately, MA all exhibited high levels of resistance to Pounce with resistance ratios of 90.60, 93.50, and 76.30-fold respectively.
    • Comparison of Neonicotinoid Use Patterns for Silverleaf Whitefly Management in Melons and Broccoli

      Palumbo, John C.; Muliis, Clay Jr.; Reyes, Francisco; Amaya, Andreas; Lesdesma, Luis; Cary, Lisa; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Studies were conducted in 1998 and 1999 to evaluate three neonicotinoid insecticides for control of silverleaf whiteflies in melons and broccoli plots at the Yuma Agricultural Center. The results of these studies demonstrate that these insecticide uses offer vegetable growers management alternatives for controlling whiteflies comparable to what they have experienced with Admire®. In our spring trials, we applied Platinum® at planting, as a split application, and as a sidedress application. All methods provided whitefly efficacy similar to that provided by Admire. However, the split and sidedress applications provided more consistent residual control than Platinum applied at planting. Because of the mobility of the product in the soil, growers may have more flexibility for effectively applying the material post-planting. In addition, Assail, was applied as a foliar spray at various densities. Under spring growing conditions, applications of Assail provided significant whitefly control when initiated at low densities. Under high whitefly densities on fall melons and broccoli, application of Assail was capable of significantly reducing existing immature populations. These evaluations suggests that Platinum and Assail may be promising alternatives to Admire. We presume that it may allow growers to use the product in a responsive manner as a side dress (Platinum) or as a foliar (Assail) rather than having to rely on prophylactic Admire applications at planting.
    • Management of Western Flower Thrips in Head Lettuce with Conventional and Botanical Insecticides

      Palumbo, John; Mullis, Clayton Jr.; Reyes, Francisco; Amaya, Andreas; Ledesma, Luis; Cary, Lisa; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Studies were conducted in three independent field trials to evaluate the efficacy of conventional and botanical insecticides against western flower thrips in head lettuce. Trials were conducted in spring lettuce under moderate and heavy populations pressures. Actara and Avaunt, two new experiential insecticides did not significantly control adults and provided only marginal activity against the larvae when applied alone. Combination of these products with either Lannate or Warrior significantly enhanced control, but usually not greater than that shown from the Lannate or Warrior applied alone. Several botanical products were evaluated (azadirachtin, pyrethrins, crop oils and garlic). Unfortunately, none of the botanical products significantly reduced thrips numbers to economically acceptable levels of control. Similar to previous studies, our results suggest that even the most efficacious products appeared to maintain thrips populations at constant levels and not necessarily reducing their numbers. More research needs to be conducted to determine the proper timing of applications to achieve optimal thrips using both conventional and botanical insecticides.
    • Impact and Management of Western Flower Thrips on Romaine Lettuce

      Palumbo, John; Mullis, Clayton Jr.; Reyes, Francisco; Amaya, Andreas; Ledesma, Luis; Cary, Lisa; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      A season-long study was conducted to evaluate the efficacy of several conventional, experimental and bio-based insecticide combinations used in rotation against western flower thrips (WFT) in romaine lettuce. Results from this study showed that several insecticide rotational programs provided good control of WFT populations throughout the season. Adult abundance peaked just prior to the fourth spray on 28 March, whereas larvae numbers peaked about 2 weeks earlier on March 13. Fluctuations of larval and adult populations observed from weekly samples suggests that greater than 3 WFT generations developed during the experimental period. Averaged across all sample dates, the Success, Lannate and Warrior based rotations maintained adult and larval populations at significantly lower levels than all other treatments. The Bio-based, organic rotations (Neem/Garlic/COC/Sulfur/Diatect) did not differ from the untreated check. Percentage reduction of WFT larvae and adults compared with the untreated control was significantly greater following sprays which contained Success combinations. Consistent with reduction in WFT numbers, the Success/Lannate/Warrior, and Dimethoate based rotations resulted in significantly greater yields and less damage. Regression analysis suggests that larvae and total thrips abundance more consistently describes the variation measured in plant weights. Overall, this preliminary data further indicates that maintaining WFT abundance at low levels is important for maintaining romaine yield and quality.
    • New Chemistry and Pyrethroid Combinations for Lepidopterous Pest Control in Broccoli

      Umeda, K.; MacNeil, D.; Lund, N.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Success, Proclaim, and Avaunt were efficacious when applied alone or in combination with the pyrethroids, Warrior or Mustang. Warrior and Mustang alone also provided excellent control of the cabbage looper (Trichoplusia ni, CL) and diamondback moth (Plutella xylostella, DBM) at all rating dates for 3 weeks after a single application. Low infestation levels of the pests were attributed to the effectiveness of the insecticides.
    • Predicting Dispersal by Whitefly Parasitoids

      Byrne, David N.; Bellamy, David E.; Byrne, David N.; Baciewicz, Patti; Department of Entomology (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      These experiments were designed to examine short-range dispersal by the small whitefly parasitoid Eretmocerus eremicus that takes place within the confines of a specifically defined habitat. We were specifically concerned with the impacts of sex and mating status on their dispersal. We hoped to construct predictive models concerning dispersal. In a vertical flight chamber we found that female flight duration was significantly longer (11 times) than that of males and that unmated parasitoids flew approximately three times longer than mated individuals. In field studies 87% of the 4,153 parasitoids captured were males. This occurred in spite of sex ratios being near 1:1 upon release. The difference in dispersal characteristics between males and females may be resource based. It is felt that certain requirements were met within our field plots for males that were not met for females. It is important for males to find mates and they may have done so inside release containers or in close proximity to release sites. While females have a similar requirement, they must also find whitefly hosts to parasitize. It can be assumed that each sex took active steps to accomplish different goals. Males were searching the immediate area of the release sites where mates were plentiful, while females were leaving the 33 ft. radius plots in search of whitefly hosts. We were able to verify models for male dispersal (75% of males were predicted to disperse within 13.5 ft.). Our models predicted that 50% of females would be found within 82 ft. This information will useful when describing movement by E. eremicus and other small insects. It should prove useful when defining release techniques for parasitoids being used as biological control agents.
    • Field Evaluation of Cauliflower Varieties Grown in Southwest Low Desert Soils

      Zerkoune, Mohammed A.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Selection of adapted varieties to environmental factors and soil types are paramount to growing profitable cauliflower crops. Varieties are selected for uniform maturity, field holding capability, head size, shape and color. The objective of this demonstration trial is to evaluate new and existing commercial varieties under standard field conditions. Seven varieties were planted in a single row and evaluated at Yuma Agricultural Research Center (YAC) for their agronomic characteristics and their commercial values. All varieties tested performed well with an overall rating of 4 or better, indicating that when planted under similar conditions and planting dates, these varieties are expected to do well. However a significant head weight and head diameter difference was observed among varieties tested.
    • Lettuce Variety Trial

      Clark, L. J.; Walser, R.; Carpenter, E. W.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Eleven head lettuce varieties and four leaf lettuce varieties were grown in a replicated small plot trial on the Safford Agricultural Center in 1998. Desertgreen variety of head lettuce from Harris Moran produced a crop with the best head weight, size and firmness rating. Premiere variety followed closely behind. Of the leaf lettuce varieties tested, Saguaro Romaine produced the best quality and quantity product. Per acre yields are calculated for each variety in the study.
    • Field Evaluation of Broccoli Varieties Grown in Southwest Low Desert Soils

      Zerkoune, Mohammed A.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Based on acreage, broccoli is the third largest vegetable crop in Yuma County, after head lettuce, and romaine. It generates over $36 000000 a year. Efforts are continuously made by both seed industry and growers to grow better varieties that respond to consumers’ choice. Selection of newly adapted varieties is made based on agronomic performance as well as commercial value. Stand uniformity, disease resistance, color, head shape, and head size are among characteristics that are evaluated. The objective of this demonstration trial is to evaluate the characteristics of new varieties grown under standard cultural practices. Twelve varieties were tested at Yuma Agricultural Research Center. No incidence of disease was observed and the overall evaluation rating was greater than 4 indicating that all varieties tested will do well under similar growing conditions and planting date. Significant head diameter and plant height were observed among varieties tested.
    • Evaluation of Fungicide Performance for Control of Powdery Mildew on Lettuce in 2000

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Powdery mildew on lettuce is caused by the fungus Erysiphe cichoracearum. This disease is favored by moderate to warm temperatures and dry weather conditions. Several potential new fungicides were evaluated for control of powdery mildew on lettuce in 2000. Powdery mildew appeared in our plots by Feb 9 and reached high levels by plant maturity on Mar 2. Nontreated lettuce plants were heavily infected with powdery mildew at plant maturity, whereas the disease ranged from low to virtually nonexistent levels in plots treated with BAS 500, Quadris+Actigard, Flint, Flint+Actigard, Flint alternated (alt.) with Trilogy, Rally, Microthiol, EksPunge alt. with Microthiol, KHHUBF-99-001, Quinoxyfen, Flint alt.with Serenade, Rally alt. with Serenade, and Serenade alt. with Microthiol. These compounds have various modes of action, and some could be available for “organic” production. The future 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.
    • Performance of New Chemistries for Control of Powdery Mildew of Cantaloupe in 1999

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Powdery mildew on melons is an annual disease problem in Arizona. Sphaerotheca fuliginea is the plant pathogenic fungus that causes powdery mildew of cucurbits, which include cantaloupe, honeydew, watermelon, cucumber and squash. When environmental conditions are favorable, disease incidence and severity can reach economically significant levels. Factors that favor development of powdery mildew on melons include moderate temperatures and relative humidity, succulent plant growth, and reduced light intensity brought about by a dense plant canopy. Potential new fungicides were evaluated and compared to existing chemicals for control of powdery mildew of cantaloupe in a field trial conducted during the spring of 1999 at the Yuma Agricultural Center. A high level of disease had developed by crop maturity (June 29). On nontreated plants 43% of the upper leaf surface was covered by powdery mildew, whereas the level on the underside of leaves was 78%.. All of the 34 different treatments significantly reduced the level of powdery mildew on both sides of leaves, compared to nontreated plants. The best treatments among those tested with respect to disease control on the underside of leaves, where disease control is more difficult than on the tops of leaves, included Topsin+Trilogy, Benlate, Benlate+Trilogy, Quadris, A815, Topsin+Microthiol, and Topsin. The potential availability of new chemistries for management of powdery mildew of cantaloupe and other cucurbits could help improve overall control of powdery mildew as well as the implementation of fungicide resistance management strategies, which strive to minimize the risk of resistance development by the pathogen to these compounds.
    • New Insecticides for Diamondback Moth Control in Cabbage

      Umeda, K.; MacNeil, D.; Roberts, D.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      At 3 days after the first application, RH-2485, Success, Proclaim, Avaunt, and Larvin reduced the total number of diamondback moth (DBM) larvae to less than 2.0 larvae per 10 plants compared to the untreated that had 7.0 larvae/10 plants. Alert, Kryocide, and S-1812 treated cabbage exhibited 4.0 to 5.0 larvae/10 plants and Lannate was intermediate with 2.7 total larvae/10 plants. Following a second application, Success and Proclaim completely controlled DBM for one week. Success, Proclaim, Alert, and Larvin continued to offer very good control of DBM for two weeks after the second application. S-1812 performed similarly to Lannate.
    • Pro-active Management of Beet Armyworm (Spodoptera exigua) Resistance to IGRs, Tebufenozide and Methoxyfenozide

      Moulton, John K.; Pepper, David A.; Dennehy, Timothy J.; Byrne, David N.; Baciewicz, Patti; Extension Arthropod Resistance Management Laboratory, Department of Entomology (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Susceptibility to tebufenozide and methoxyfenozide of beet armyworm (Spodoptera exigua) from the southern United States and Thailand was determined through exposure of first and third instar larvae to dipped cotton leaves. LC50 estimates of first instar larvae ranged from 0.377 to 32.7 micrograms of tebufenozide per milliliter and 0.034 to 11.5 micrograms of methoxyfenozide per milliliter. LC₅₀ estimates of third instar larvae ranged from 4.37 to 715 micrograms of tebufenozide per milliliter and 0.393 to 47.4 micrograms of methoxyfenozide per milliliter. These estimates translated into 87-fold and 164-fold decreases in susceptibility to tebufenozide and 338-fold and 121-fold decreases in susceptibility to methoxyfenozide of first and third instar larvae from a Thailand strain when compared to the most susceptible of eight United States populations evaluated. Among the United States field populations evaluated, a collection from Belle Glade, Florida was the most susceptible and one taken near Parker, Arizona was the least susceptible. Selection of the Thailand population with tebufenozide or methoxyfenozide resulted in significant reductions in susceptibility to both analogs, indicating a common mechanism of resistance. Isolation and characterization of resistance will provide information that will be helpful for pro-active management of resistance for this valuable group of insecticides in the United States.
    • Comparison of New Fungicides to Manage Sclerotinia Leaf Drop of Lettuce in 2000

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Sclerotinia minor and S. sclerotiorum are the two soil-borne pathogenic fungi that cause Sclerotinia leaf drop in Arizona. Moist soils and moderate temperature favor this disease. Some new fungicides in development were evaluated for control of leaf drop on lettuce during the winter vegetable growing season of 1999-2000. Sclerotia of each pathogen were applied to plots after thinning and just before the first of two applications of test compounds. In this trial, the final count of dead lettuce plants usually was numerically reduced, compared to nontreated plots, in plots infested with either pathogen that were treated with the standard compounds Ronilan or Rovral as well as the experimental compound Medallion; however, the reduction was significant only in plots infested with Sclerotinia sclerotiorum. The number of dead plants in plots infested with either Sclerotinia minor or S. sclerotiorum was significantly reduced by another experimental chemistry, Fluazinam. Finally, a biological control product, Serenade, significantly reduced disease in plots containing S. minor, but not S. sclerotiorum. 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 caused by S. minor.
    • Seasonal Abundance and Control of the Lettuce Aphid, Nasonovia ribisnigri, on Head Lettuce in Arizona

      Palumbo, John C.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Small plot studies were conducted in 1999/2000 to examine the population abundance and control of the lettuce aphid on winter and spring head lettuce crops. Seven, 0.25 acre planting of head lettuce were established beginning in October with final harvest occurring in April. Replicated plots within several planting were treated with an Admire treatment at planting, a sidedress application of Platinum post-planting or allowed to remained untreated. Lettuce aphids were first detected in our experimental area on Feb 14 in PD 3 in untreated plants. Temperature had an important influence upon lettuce aphid development based on our field observations. Population appeared to increase in early March when the average daily temperature was about 65 °F. We observed a sharp decline in population abundance in April where daytime highs exceeded 90 °F. We were surprised by the marginal level of lettuce aphid control provided by the systemic insecticides. Lettuce treated with Admire in the early planting dates appeared to prevent lettuce aphids from significantly infesting lettuce heads at harvest. In the later planting dates, both Admire and Platinum contained significantly fewer aphids and infested plants than the untreated control. However, lettuce aphids in the last 3 planting dates were able to colonize plants and infest a larger proportion of heads at levels not considered commercially acceptable. We are hesitant to draw conclusions from our results collected from a single season , and plan to replicate this work next year under different environmental conditions and higher rates of Admire and Platinum.