• 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.
    • Susceptibility of Arizona Whiteflies to Neonicotinoid Insecticides and IGRs: New Developments in the 1999 Season

      Li, Yongsheng; Dennehy, Timothy J.; Li, Xiaohua; Wigert, Monika E.; Byrne, David N.; Baciewicz, Patti; Extension Arthropod Resistance Management Laboratory, Department of Entomology (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Whiteflies are serious pests of cotton, melons, and winter vegetables in Arizona’s low deserts. Successful management of whiteflies requires an integrated approach, a critical element of which is routine pest monitoring. In this paper we report findings of our 1999 investigations of resistance of Arizona whiteflies to insect growth regulators (IGRs) and neonicotinoid insecticides. Whiteflies collected from cotton fields, melon fields and greenhouses were tested for susceptibility to imidacloprid (Admire /Provado), and two other neonicotinoid insecticides, acetamiprid and thiamethoxam, and to two insect growth regulators (IGRs), buprofezin (Applaud ) and pyriproxyfen (Knack ). Contrasts of 1999 and 1998 results indicated increased susceptibilities, on average, to both imidacloprid and buprofezin of whiteflies collected from cotton. A cropping system study showed that whiteflies collected from spring melons had significantly lower susceptibility to imidacloprid than those collected from cotton or fall melons. The opposite was found for pyriproxyfen, to which whiteflies from cotton and fall melons had lower susceptibility than those from spring melons. As in 1998, whiteflies with reduced susceptibility to imidacloprid continue to be found in certain locations, particularly in spring melon fields and greenhouses. Results of our laboratory bioassays on susceptibility of Arizona whiteflies to neonicotinoid insecticides provided evidence of a low order cross-resistance between imidacloprid, acetamiprid and thiamethoxam. Monitoring in 1999 provided the first evidence of reduced susceptibility of Arizona whiteflies to pyriproxyfen.
    • 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.
    • Fall Planted, Late Maturing Onion 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)
      Thirteen late maturing onion varieties were planted in the fall of 1998 and grown in a replicated small plot trial on the Safford Agricultural Center. Bulbs were pulled and the tops removed in early June. Three NuMex varieties, Mesa, Starlite and BR1, produced the best yields. Yields are shown in tabular form together with size distribution and quality characteristics.
    • Population Dynamics and Distribution of Aphid Species on Head Lettuce in the Yuma Valley

      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 the 1999/2000 growing season to examine the population dynamics and field distribution of aphid species 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. Plant samples were conducted weekly to estimate the numbers of both alate (winged) and apterous (wingless) green peach aphids, potato aphids, cowpea aphids and lettuce aphids. Lettuce aphids were more abundant this spring than anticipated, which may indicate that lettuce aphid may be a new pest for Yuma growers. However, based on a single years data, it is difficult to measure the threat that this aphid poses to the lettuce industry. Planting date and temperature likely has a strong influence on seasonal abundance of lettuce aphids. Similarly, the consistent appearance of cowpea aphids during the season was surprising , considering that it has seldom been observed on desert lettuce. Perhaps most surprising though was the low population abundance of green peach and potato aphids in out plots. Part of this unusual event may be due to the unseasonably warm, dry growing season that was experienced this year.
    • 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.
    • 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 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.
    • Screening New Herbicides for Weed Control in Head and Leaf Lettuces and Broccoli

      Umeda, Kai; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      In preemergence (PREE) herbicide testing, all three lettuces, head, romaine, and red leaf, exhibited some tolerance to carfentrazone, sulfentrazone, flumetsulam, rimsulfuron, and thifensulfuron while giving effective weed control. In postemergence (POST) testing, cloransulam and flumetsulam controlled weeds at the lowest applied rates while lettuces were safe to cloransulam at 0.01 lb AI/A and flumetsulam at 0.03 lb AI/A. Imazamox was safe on lettuces at 0.01 lb AI/A and controlled weeds at 0.007 lb AI/A. For broccoli, sulfentrazone, fluroxypyr, and thifensulfuron applied PREE demonstrated reasonable safety and weed control. Cloransulam, flumetsulam, and fluroxypyr applied POST on broccoli exhibited adequate crop safety and good weed control.
    • Herbicide Screen for Melons

      Umeda, K.; MacNeil, D.; Lund, N.; Roberts, D.; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Seventeen herbicides recently gaining registrations in corn, soybeans, or other major crops were evaluated in screening tests for potential use in melons. In a preemergence herbicide screening test, flumioxazin, dimethenamid, halosulfuron, and s-metolachlor demonstrated melon crop safety at rates higher than rates for effective weed control. In a postemergence screening test, halosulfuron and rimsulfuron gave acceptable weed control with adequate crop safety. Flumetsulam and thifensulfuron appeared to offer some acceptable weed control with a very narrow margin of crop safety. Herbicides that did not offer adequate melon crop safety or acceptable weed control in the screening tests were carfentrazone, sulfentrazone, cloransulam, flumiclorac, fluthiamide/metribuzin, imazamox, isoxaflutole, triflusulfuron, primisulfuron/prosulfuron, and clomazone.
    • Squash 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)
      Five Zucchini varieties and four yellow crook/straight-necked squash were grown in a replicated small plot trial on the Safford Agricultural Center in 1998. Varieties were picked regularly during the growing season. Yields are shown in tabular form and also graphically to indicate how each variety performed throughout the season.
    • Melon 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)
      Seven cantaloupe varieties and two Honeydew melon varieties were grown in a replicated small plot trial on the Safford Agricultural Center in 1998. Varieties were picked regularly during the growing season. Yields are shown in tabular form to indicate how each variety performed during the season.
    • 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.
    • Effect of Cultivar and Actigard on Development of Powdery Mildew on Lettuce

      Matheron, Michael E.; Porchas, Martin; Byrne, David N.; Baciewicz, Patti (College of Agriculture, University of Arizona (Tucson, AZ), 2000-08)
      Nine different cultivars of lettuce were planted at the Yuma Valley Agricultural Center. Plants were treated four times with two different rates of Actigard. Control plants were not treated. Near plant maturity (Mar. 23, 2000) the severity of powdery mildew was recorded. Among nontreated plants, Cibola, Conquistador, and Coolguard had the lowest levels of powdery mildew. On the other hand, Bos 9003 and Mohawk had significantly higher levels of powdery mildew than all other tested cultivars. Four applications of Actigard at a rate of 14 g. of active ingredient per acre significantly reduced the level of powdery mildew on all nine tested cultivars of lettuce. On two lettuce cultivars, powdery mildew was significantly lower when treated with Actigard at the 28 g. a.i./A rate when compared to the 14 g. a.i./A rate. No evidence of phytotoxicity was apparent on plants treated with Actigard. This study suggests that lettuce cultivars differ in susceptibility to powdery mildew. Also, Actigard was able to provide added protection against powdery mildew for all tested lettuce cultivars.
    • 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.
    • 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.
    • 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.