Progress 07/01/08 to 09/30/12
Outputs
OUTPUTS: Phytophthora root and crown rot of peppers, caused by the oomycete pathogen Phytophthora capsici, causes significant losses in Arizona commercial production fields. This research project focused on four specific performance goals: 1) evaluating and comparing efficacy of fungicides, including biofungicides; 2) assessing the potential use of cultivar resistance and soil solarization; 3) examining the role of weeds as potential hosts and sources of inoculum for P. capsici in pepper fields; and 4) characterizing pathogen isolates in Arizona pepper production fields with respect to virulence and mating type. The efficacy of several conventional fungicides and two biofungicides were evaluated in three greenhouse and two field trials. The effect of method of fungicide placement in soil on the degree of disease reduction achieved was also examined. One greenhouse and one field trial were conducted to evaluate the potential of genetic resistance and soil solarization, respectively, for use as tools for management of Phytophthora root and crown rot on pepper in Arizona. The capacity of weed and crop roots to support growth and sporulation of P. capsici was assessed in a laboratory study. Mating types of P. capsici isolates from Arizona pepper fields was determined to assess the potential for production of long-lived oospores. Finally, two greenhouse trials were conducted to evaluate the virulence or aggressiveness of 12 different isolates of P. capsici from chile pepper fields in southeastern Arizona. Data and findings from these studies were presented to growers and other interested clientele at pepper oriented conferences and meetings attended by crop health researchers. PARTICIPANTS: Michael Matheron, Principal Investigator. Designed and directed described experiments. Martin Porchas, Research Specialist. Initiated, monitored, and completed described experiments. TARGET AUDIENCES: Pepper growers, Pest Control Advisors, and other interested clientele. Information will be made available to target audiences in workshops, extension educational meetings, and publications. PROJECT MODIFICATIONS: No changes made.
Impacts
Studies focused on the biology, ecology, and management of Phytophthora root and crown rot of chile peppers in Arizona yielded data useful for growers and other clientele with an interest in this disease and its successful management. The mean reduction in dead pepper plants due to soil treatment every 2 weeks with the conventional fungicides Ridomil Gold, Revus, Omega, V-10208, Forum, Presidio, Zampro, and Ranman for three greenhouse trials was 90, 87, 73, 69, 64, 62, 59, and 50%, respectively, and for two field trials was 38, 13, 33, 34, 31, 40, 25, and 52%, respectively. Fungicides were applied as a soil drench in greenhouse trials and as a directed spray to the base of plants and surrounding soil prior to furrow irrigation in field trials. More effective exposure of roots to fungicides by soil drench compared to soil surface spray prior to furrow irrigation may explain the generally higher efficacy of most tested products in greenhouse compared to field trials. Tenet and Soilgard, two products containing biological active ingredients, were tested in some trials and did not provide meaningful reductions in disease. One greenhouse and one field trial were conducted to evaluate the potential of genetic resistance and soil solarization, respectively, for use as tools for management of Phytophthora root and crown rot on pepper in Arizona. No source of useful genetic resistance to Phytophthora blight was detected among the pepper plant breeding selections tested. Also, temperatures recorded in solarized soil were not high enough to significantly reduce the amount of P. capsici in soil. A laboratory inoculation trial of crop and weed plant roots demonstrated that the pepper pathogen P. capsici could colonize and sporulate on all plant roots tested. The existence of both mating types of P. capsici in the southeastern Arizona pepper production region was demonstrated with a mating experiment conducted in the laboratory. Two greenhouse trials, conducted to evaluate the virulence or aggressiveness of 12 different isolates of P. capsici from chile pepper fields in southeastern Arizona, revealed that most tested isolates were highly pathogenic and aggressive. Data from these studies suggest that several fungicides, if properly applied to the root zone of plants, can be effective components of an integrated disease management program for Phytophthora root and crown rot on pepper plants. The major chile pepper grower in Arizona has used the data from this research to improve management of Phytophthora root and crown rot.
Publications
- Matheron, M.E., and Porchas, M. 2012. Effect of fungicide type and placement on stem cankers caused by Phytophthora capsici on pepper. Proceedings of the 21st International Pepper Conference, Naples, Fl. pg. 37.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Phytophthora capsici can cause significant losses in pepper plantings. Timely application of fungicides can be a critical management strategy for Phytophthora root and crown rot. Greenhouse and field trials were conducted in Arizona in 2010 and 2011 to evaluate fungicide active ingredients as well as methods of application with the goal of optimizing management of Phytophthora root and crown rot on peppers. Depending on the trial, soil was naturally or artificially infested with P. capsici. Fungicides were applied as a soil drench in greenhouse trials and as a directed spray at the base of plants and soil surface in field trials. Plants in greenhouse trials were watered daily and those in field trials received a thorough irrigation weekly. In all trials, plants were subjected to high soil moisture conditions to favor disease development. Application frequency of fungicides was at 2-week intervals. Among fungicides tested in three greenhouse trials during 2010 and 2011, application of mefenoxam (Ridomil Gold) reduced plant mortality by 90% compared to nontreated plants. In the same trials, mean reduction in plant mortality provided by other tested products was 87% for mandipropamid (Revus), 73% for fluazinam (Omega), 69% for V-10208, 64% for dimethomorph (Forum), 62% for fluopicolide (Presidio), 59% for ametoctradin+dimethomorph (Zampro), and 50% for cyazofamid (Ranman). In two field trials conducted in 2010 and 2011, reduction in plant mortality due to fungicides, when compared to nontreated plots, was 52% for cyazofamid, 40% for fluopicolide, 38% for mefenoxam, 34% for V-10208, 33% for fluazinam, 31% for dimethomorph, 25% for ametoctradin+dimethomorph, and 13% for mandipropamid. Considering the combined data from all fungicides tested in 2010 and 2011, the mean reduction in plant mortality in greenhouse compared to field trials was 69% and 33%, respectively. Data suggest that application of fungicides as a directed spray to the base of the plant and bed surface was inferior to application of products in water to thoroughly treat the plant root zone. Evaluation of both fungicide application methods in the field will be carried out this year. Data from these trials suggest that several fungicides, when properly applied to the plant root zone, can be effective components of an integrated disease management program for Phytophthora root and crown rot on pepper plants. PARTICIPANTS: Michael Matheron, Principal Investigator. Designed and directed described experiments. TARGET AUDIENCES: Growers, Pest Control Advisors, and other interested clientele. Information will be made available to target audiences in workshops and extension educational meetings. PROJECT MODIFICATIONS: No changes made.
Impacts
Differences in efficacy were significant for some products. Also, efficacy achieved in greenhouse trials, where products were drenched into soil, were higher than those achieved in field trials, where products were sprayed onto bed surface. A field trial planned for this year will examine the effect of drench versus soil surface application on effectiveness of fungicides in control of Phytophthora root and crown rot on pepper.
Publications
- No publications reported this period
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: The oomycete pathogen Phytophthora capsici can cause extensive losses in pepper plantings. Fungicides are an important component of a Phytophthora disease management system, when used in combination with other management practices such as crop rotation, raised beds, and water management. Several fungicides have recently been registered and some additional new chemistries are being developed with activity against oomycete pathogens, including Phytophthora. Two greenhouse trials and a field trial were conducted in 2010 to evaluate these individual products for their ability to suppress development of crown and root rot on pepper plants in the presence of Phytophthora capsici. All trials were conducted at The University of Arizona Yuma Agricultural Center. A chile pepper (variety AZ 20) transplant was placed into either a peat-based potting mix (first experiment) or a silty clay loam field soil (second experiment) infested with P. capsici within a series of 500 ml capacity plastic pots. The soil in each of the 10 replicate pots per treatment was drenched with one of the test products at the initiation of the trial and 14, 28 and 42 days later. In the field trial, the same chile pepper variety was seeded into beds and plots were established in the resulting planting. Plots were established in a randomized complete block design, with five replicates per treatment and each replicate plot containing 15 plants within a 15-ft-long length of raised bed. Soil in plots was infested on June 29 by placing vermiculite (150 ml) containing P. capsici into a furrow 15 feet long and 1 inch deep next to plants in each plot, then vermiculite was covered with soil. Treatments were applied with a carbon dioxide sprayer that delivered 50 ml of spray solution to the base of each plant and the surrounding soil. Products were applied when P. capsici was introduced into plots as well as 14, 28 and 42 days after infestation of soil. Plants were irrigated every 7 to 10 days by furrow irrigation for the duration of the trial. Greenhouse and field trials were terminated about 2-months after initiation. For both greenhouse trials, compared to plants grown in infested nontreated potting mix or soil, which all died, the percent reduction in dead plants at the conclusion of the trials for treated plants was 85 for Ridomil Gold, 80 for Revus, 65 for Forum, 60 for Omega and V-10208, 55 for Presidio, 45 for Zampro, and 25 for Ranman. For the field trial, again compared to nontreated plants in infested soil, which experienced 52% mortality, the percent reduction in dead plants for treated plants was 60 for Ranman, 56 for Presidio and V-10208, 52 for Forum and Omega, 48 for Ridomil Gold, and 15 for Revus and Zampro Data will be presented at meetings with growers and other clientele with an interest in pepper disease control and fungicide efficacy. PARTICIPANTS: Michael Matheron, Principal Investigator. Designed and directed experiments described. TARGET AUDIENCES: Growers, Pest Control Advisors, and other interested clientele. Information will be made available to target audiences in workshops and extension educational meetings. PROJECT MODIFICATIONS: No changes made.
Impacts
Differences in efficacy were substantial for some products when comparing greenhouse to field trial data. Presented data should be considered preliminary until substantiated by additional trials.
Publications
- No publications reported this period
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: The oomycete pathogen, Phytophthora capsici, can cause extensive losses in pepper plantings. Fungicides are an important component of a Phytophthora disease management system, when used in combination with other management practices such as crop rotation, raised beds, and water management. Several new fungicides are being developed with known activity against oomycete pathogens, including Phytophthora. A field trial was conducted in the summer of 2009 to evaluate these new chemistries alone or in treatment programs for efficacy in suppressing development of crown and root rot on pepper plants grown in soil artificially infested with Phytophthora capsici. This trial was conducted at The University of Arizona Yuma Agricultural Center in a planting of chile peppers (variety AZ20). Plots were established in a randomized complete block design, with five replicates per treatment and each replicate plot containing 15 plants within a 15-ft-long length of raised bed. Soil in plots was infested on June 29 by placing vermiculite (150 ml) containing P. capsici into a furrow 15 feet long and 1 inch deep next to plants in each plot, then vermiculite was covered with soil. Treatments were applied with a carbon dioxide sprayer that delivered 50 ml of spray solution to the base of each plant and the surrounding soil. The products Polyversum and Tenet initially were applied 7 days before plots were infested with P. capsici. All other tested products in addition to Polyversum and Tenet were applied when P. capsici was introduced into plots as well as 14, 28 and 42 days after infestation of soil. Plants were irrigated every 7 to 10 days by furrow irrigation for the duration of the trial. Final disease incidence was assessed in late September by counting the number of chile pepper plants in each plot that had died or were permanently wilted as a result of infection by P. capsici. Compared to plants in nontreated plots, several treatments significantly reduced the number of dead plants in the presence of Phytophthora capsici. These treatments included Tenet (Trichoderma asperellum and T. gamsii), Omega (fluazinam), Presidio (fluopicolide), Revus (mandipropamid), and Tenet alternated with either Presidio or Revus. The efficacy of Tenet was inconsistent, as some treatments containing this product significantly reduced disease, whereas final disease incidence in other treatments containing Tenet did not differ from nontreated plants. Tested products that did not significantly reduce plant mortality in this trial included Ridomil Gold (mefenoxam), Forum (dimethomorph) and Ranman (cyazofamid). The results of this trial will be disseminated in written form as a Plant Disease Management Report published in the Plant Management Network website as well as at meetings with growers and other clientele with an interest in pepper disease control and fungicide efficacy. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The findings from this single field trial are promising; however, until confirmed by additional experiments, these results should be considered preliminary in nature. As such, any assessment of outcome or impact at this time would be premature.
Publications
- No publications reported this period
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Progress 07/01/08 to 12/31/08
Outputs
OUTPUTS: The oomycete pathogen, Phytophthora capsici, can cause extensive losses in pepper plantings. The first symptoms usually include a crown (stem) and root rot, which can be followed by an aerial blight of leaves, fruit, and stems in regions with frequent rainfall events. Excessive soil moisture, either from irrigation or rainfall, stimulates production of sporangia and release of zoospores, the infective propagule of the pathogen. Fungicides are an important component of a Phytophthora disease management system, when used in combination with other management practices such as crop rotation, raised beds, and water management. Several new fungicides are being developed with known activity against oomycete pathogens closely related to P. capsici. A field trial was conducted in the summer of 2008 with the objective of evaluating these new chemistries alone or in treatment programs for their efficacy in suppressing development of crown and root rot on pepper plants grown in soil naturally infested with Phytophthora capsici. This trial was conducted in a grower's field planted with the chile pepper variety AZ20. Plots were established in a randomized complete block design, with four replicates per treatment with each replicate plot (containing about 50 plants) consisting of two rows of plants, each 20-ft-long. Treatments were applied with a carbon dioxide sprayer that delivered 100 gal per acre at 35 psi. In treatment programs where the first product applied was mefenoxam, the Jul 24 application of this product was applied to the soil and base of plants; whereas all subsequent applications of materials from Jul 31 to Sep 8 were foliar. All other treatments (where mefenoxam was not applied) were applied to the base of plants and soil. The trial was initiated Jul 24 and terminated Sep 26, 2008. Treatments were applied Jul 24, Jul 31, Aug 8, Aug 15, Aug 22, Aug 29 and Sep 8, 2008. Disease progress and severity was assessed by counting the number of chile pepper plants that had died by Aug 8, 15, 22, and 29 as well as by Sep 8 and 26. These dates were the 3rd through the 7th and final treatment dates plus a final disease severity determination 18 days after the last treatment. Due to highly variable development of disease among replicate plots of the treatments within this field trial, which is common for Phytophthora crown and root rot development in commercial fields, statistically significant differences among treatments could not be determined for any of the data sets collected. Although not statistically significant, the mean number of dead plants caused by Phytophthora was reduced from 21 to 74% by the tested treatment programs, compared to nontreated plots, suggesting that some treatments tended to reduce disease severity. The treatment programs that reduced the number of dead plants by at least 45% compared to nontreated plants included the following fungicides; cyazofamid, dimethomorph, fluazinam, fluopicolide, mandipropamid, and mefenoxam. This trial will be repeated with treatments containing the same fungicides with the goal of achieving data that can be subjected to statistical analysis. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Due to the high variability within the data, statistically significant differences between treatments could not be obtained from this trial. Since we do not have strong data on which to base a valid outcome or impact, further evaluation of these fungicides in additional field trials will be needed before outcomes or impacts can be generated.
Publications
- No publications reported this period
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