Michael E Matheron

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Scholarly Contributions

Chapters

• Matheron, M. E. (2017). Damping Off. In Compendium of Lettuce Diseases and Pests, 2nd edition(pp 31-32). St. Paul, MN: The American Phytopathological Society.
• Matheron, M. E., & Olsen, M. (2017). Plant Pathology. In Arizona Master Gardener Manual(pp 89-104). Tucson, AZ: College of Agriculture and Life Sciences, University of Arizona.
• Matheron, M. E., Kahn-Rivadeneira, P., & Nunez, J. (2017). Bird Damage. In Compendium of Lettuce Diseases and Pests, 2nd edition(pp 129-130). St. Paul, MN: The American Phytopathological Society.
• Matheron, M., Gullino, M., Katan, ., & Garibaldi, A. (2012). Fusarium wilts of lettuce and other salad crops. In Fusarium Wilts of Greenhouse Vegetable and Ornamental Crops(pp 175-184). St. Paul.

Journals/Publications

• Liu, B., Feng, C., Matheron, M. E., & Correll, J. C. (2018). Characterization of Foliar Web Blight of Spinach, Caused By Pythium aphanidermatum, in the Desert Southwest of the United States. Plant Disease, 102, 608-612.
• Matheron, M. E., & Porchas, M. (2018). Assessment of fungicides for managing powdery mildew of lettuce, 2017.. Plant Disease Management Reports, 12:V002.
• Matheron, M. E., & Porchas, M. (2018). Comparison of fungicides for managing powdery mildew of muskmelon, 2017.. Plant Disease Management Reports, 12:V046.
• Matheron, M. E., & Porchas, M. (2018). Effectiveness of fungicides for managing downy mildew of lettuce, 2017.. Plant Disease Management Reports, 12:V003.
• Matheron, M. E., & Porchas, M. (2018). Evaluation of fungicides for management of Fusarium wilt of lettuce, 2017.. Plant Disease Management Reports, 12:V133.
• Matheron, M. E., & Porchas, M. (2018). Evaluation of fungicides for managing Sclerotinia lettuce drop, 2017.. Plant Disease Management Reports, 12:V004.
• Matheron, M. E., & Porchas, M. (2018). Impact of Summer Flooding on Viability of Sclerotinia minor and S. sclerotiorum Sclerotia in Soil. Plant Health Progress, 19, 15-18.
• Matheron, M. E., Feng, C., Correll, J. C., & Koike, S. T. (2018). Evaluation of spinach varieties for downy mildew resistance, Monterey County, CA, 2017.. Plant Disease Management Reports, 12:V132.
• Matheron, M. E., Porchas, M., & Pryor, B. M. (2018). Comparison of lettuce varieties for resistance to Fusarium wilt, 2017. Plant Disease Management Reports, 12:V134.
• Correll, J. C., Feng, C., Matheron, M. E., Porchas, M., & Koike, S. T. (2017). Evaluation of spinach varieties for downy mildew resistance, 2017.. Plant Disease Management Reports, 11:V122.
• Matheron, M. E., & Porchas, M. (2017). Assessment of fungicides for managing downy mildew of spinach, 2016.. Plant Disease Management Reports, 11:V002.
• Matheron, M. E., & Porchas, M. (2017). Comparison of fungicides to manage downy mildew of lettuce, 2016.. Plant Disease Management Reports, 11:V005.
• Matheron, M. E., & Porchas, M. (2017). Effectiveness of fungicides for managing Sclerotinia drop of lettuce, 2016.. Plant Disease Management Reports, 11:V006.
• Matheron, M. E., & Porchas, M. (2017). Evaluation of fungicides for managing powdery mildew of muskmelon, 2016.. Plant Disease Management Reports, 11:V003.
• Matheron, M. E., & Porchas, M. (2017). Examination of fungicides for managing powdery mildew of lettuce, 2016.. Plant Disease Management Reports, 11:V004.
• Matheron, M. E., Correll, J. C., Porchas, M., & Feng, C. (2017). Assessment of fungicides for managing downy mildew of spinach, 2017.. Plant Disease Management Reports, 11:V121.
• Matheron, M. E., Porchas, M., & Pryor, B. M. (2017). Evaluation of conventional fungicides and biofungicides for managing Fusarium wilt of lettuce, 2016.. Plant Disease Management Reports, 11:V123.
• Matheron, M. E., Porchas, M., & Pryor, B. M. (2017). Evaluation of lettuce varieties for resistance to Fusarium wilt, 2016.. Plant Disease Management Reports, 11:V124.
• Correll, J. C., Matheron, M. E., Koike, S. T., Porchas, M., Pavel, J., & Feng, C. (2016). Evaluation of biofungicides and conventional fungicides for management of downy mildew on spinach, 2015. Plant Disease Management Reports, 10:V106.
• Matheron, M. E., & Porchas, M. (2016). Comparison of fungicides for management of Sclerotinia lettuce drop, 2015. Plant Disease Management Reports, 10:V012.
• Matheron, M. E., & Porchas, M. (2016). Effectiveness of fungicides for management of powdery mildew on muskmelon, 2015. Plant Disease Management Reports, 10:V010.
• Matheron, M. E., & Porchas, M. (2016). Evaluation of fungicides for management of downy mildew on lettuce, 2015. Plant Disease Management Reports, 10:V011.
• Matheron, M. E., & Porchas, M. (2016). Evaluation of lettuce cultivars and Actigard on development of Fusarium wilt, 2015. Plant Disease Management Reports, 10:V104.
• Matheron, M. E., Correll, J. C., Koike, S. T., Saito, K., Pavel, J., & Feng, C. (2016). Evaluation of spinach varieties for downy mildew resistance, 2015. Plant Disease Management Reports, 10:V107.
• Matheron, M. E. (2015). Biology and management of Fusarium wilt of lettuce. CALS Cooperative Extension, 2.
• Matheron, M. E. (2015). Biology and management of downy mildew of lettuce. CALS Cooperative Extension, 2.
• Matheron, M. E., & Porchas, M. (2015). Comparison of fungicides for management of powdery mildew on lettuce, 2014. Plant Disease Management Reports, 9:V079.
• Matheron, M. E., & Porchas, M. (2015). Effectiveness of fungicides for management of Sclerotinia lettuce drop, 2014. Plant Disease Management Reports, 9:V078.
• Matheron, M. E., & Porchas, M. (2015). Effectiveness of nine different fungicides for management of crown and root rot of chile pepper plants caused by Phytophthora capsici. Plant Health Progress, 16(4), 5. doi:10.1094/PHP-RS-15-0028
• Matheron, M. E., & Porchas, M. (2015). Evaluation of fungicides for mangement of powdery mildew on muskmelon, 2014. Plant Disease Management Reports, 9:V080.
• Matheron, M. E., & Porchas, M. (2014). Assessment of fungicides first applied at seeding for management of Sclerotinia lettuce drop, 2013. Plant Disease Management Reports, 8: V198.
• Matheron, M. E., & Porchas, M. (2014). Effectiveness of 14 fungicides for suppressing lesions caused by Phytophthora capsici on inoculated stems of chile pepper seedlings. Plant Health Progress, 15(4), 166-171.
• Matheron, M. E., & Porchas, M. (2014). Efficacy of fungicides first applied after thinning for management of Sclerotinia lettuce drop, 2013. Plant Disease Management Reports, 8:V200.
• Matheron, M. E., & Porchas, M. (2014). Evaluation of fungicides for management of downy and powdery mildew on lettuce, 2013. Plant Disease Management Reports, 8:V199.
• Matheron, M. E., & Porchas, M. (2014). Evaluation of fungicides for management of powdery mildew on muskmelon, 2013. Plant Disease Management Reports, 8: V197.
• Matheron, M. E., & Porchas, M. (2013). Assessment of fungicides for management of powdery mildew on muskmelon, 2012. Plant Disease Management Reports, 7.
• Matheron, M. E., & Porchas, M. (2013). Comparison of fungicides for management of Sclerotinia lettuce drop, 2012. Plant Disease Management Reports, 7.
• Matheron, M. E., & Porchas, M. (2013). Evaluation of fungicides for management of powdery mildew on lettuce, 2012. Plant Disease Management Reports, 7.
• Matheron, M. E., & Porchas, M. (2013). Inhibition of stem canker growth by fungicides on pepper plants inoculated with Phytophthora capsici, 2012. Plant Disease Management Reports, 7.
• Matheron, M. E., Matheron, M. E., Porchas, M., & Porchas, M. (2013). Efficacy of fungicides and rotational programs for management of powdery mildew on cantaloupe. Plant Disease, 97, 196-200.
• Scott, J. C., Gordon, T. R., Kirkpatrick, S. C., Koike, S. T., Matheron, M. E., Ochoa, O. E., Truco, M. J., & Michelmore, R. W. (2012). Crop rotation and genetic resistance reduce risk of damage from Fusarium wilt in lettuce. California Agriculture, 66(1), 20-24.
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  Abstract: Fusarium wilt of lettuce, caused by the soilborne fungus Fusarium oxysporum f. sp. lactucae, affects all major lettuce production areas in California and Arizona. In trials at UC Davis, we found that lettuce cultivars differ significantly in susceptibility to the disease, with some leaf and romaine types highly resistant under all test conditions. For more susceptible cultivars, disease severity is strongly influenced by inoculum levels and ambient temperature. Management of Fusarium wilt requires an integrated approach that includes crop rotation to reduce soil inoculum levels and the use of resistant cultivars during the warmest planting windows.
• Scott, J., Gordon, T., Kirkpatrick, S., Koike, S., Matheron, M., Ochoa, O., Truco, M., & Michelmore, R. (2012). Crop rotation and genetic resistance reduce risk of damage from Fusarium wilt in lettuce. California Agriculture, 66, 20-24.
• Chitrampalam, P., Turini, T. A., Matheron, M. E., & Pryor, B. M. (2010). Effect of sclerotium density and irrigation on disease incidence and on efficacy of Coniothyrium minitans in suppressing lettuce drop caused by Sclerotinia sclerotiorum. Plant Disease, 94(9), 1118-1124.
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  Abstract: Field experiments were conducted over 2 years in Yuma, AZ, and Holtville, CA, to establish the relationship between soil sclerotium density of Sclerotinia sclerotiorum and the incidence of lettuce drop on different lettuce (Lactuca sativa) types under different irrigation systems, and to determine the efficacy of the biocontrol agent Coniothyrium minitans (Contans) against S. sclerotiorum on crisphead lettuce at varied sclerotium densities under different irrigation systems. There was no significant interaction of irrigation (overhead sprinkler versus furrow) with either sclerotium density or with biocontrol treatment. Lettuce drop incidence was lowest in romaine lettuce compared with crisphead or leaf lettuce at all soil sclerotium densities. There was a significant positive correlation between the sclerotial density and the percent disease incidence. Disease incidence in plots infested with 2 sclerotia/m2 of bed was not significantly higher than in control plots regardless of lettuce type. However, plots infested with 40 or 100 sclerotia/m2 of bed revealed a significantly higher disease incidence over the control in all lettuce types. A single application of Contans at planting significantly reduced the incidence of lettuce drop in all lettuce types even under high disease pressure. There were no significant differences between recommended (2.2 kg/ha) and high (4.4 kg/ha) application rates of Contans or between one or two applications of the product. © 2010 The American Phytopathological Society.
• Matheron, M. E., & Porchas, M. (2010). Evaluation of soil solarization and flooding as management tools for Fusarium wilt of lettuce. Plant Disease, 94(11), 1323-1328.
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  Abstract: Fusarium wilt of lettuce caused by Fusarium oxysporum f. sp. lactucae continues to spread and cause economic losses in Arizona lettuce fields since the initial discovery of the disease in the state in 2001. Studies were initiated to assess the potential of summer soil solarization and flooding as management tools for Fusarium wilt of lettuce in southwestern Arizona production fields. In microplot studies, lettuce plant growth in soil naturally infested with F. oxysporum f. sp. lactucae that was solarized from 2 to 8 weeks was consistently greater than growth in nonsolarized soil. Growth of lettuce in flooded soil containing the pathogen occasionally was significantly higher than in nonflooded soil; however, the effect on plant growth and health was not as consistent as that recorded for solarized soil. In four trials within a field containing F. oxysporum f. sp. lactucae, the incidence of Fusarium wilt on lettuce sown in soil after solarization was reduced from 42 to 91% compared with disease in nonsolarized plots. There was no significant benefit of a 2- over a 1-month solarization period under the conditions of these trials, where the mean soil temperature at a depth of 5 cm during a 1-month solarization period in 2005 and 2006 was 47 and 497dag;C, respectively. These findings suggest that soil solarization can be an effective tool for management of Fusarium wilt on lettuce, especially when used within an integrated program in conjunction with existing disease management tactics. © 2010 The American Phytopathological Society.
• Matheron, M. E., & Porchas, M. (2009). Impact of different preplant cultural treatments on survival of Phytophthora nicotianae in soil. Plant Disease, 93(1), 43-50.
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  Abstract: During the life of a citrus planting, the population of Phytophthora pathogens can build to significant levels in orchard soil. A study was initiated to examine the impact of some nonchemical cultural practices on survival of P. nicotianae, the most prevalent Phytophthora sp. in Arizona citrus groves, in soil formerly planted to citrus. In three trials over a 3-year period, P. nicotianae could not be detected at a depth of 10 cm after soil naturally infested with the pathogen was subjected to a dry summer fallow period of at least 31 days in the desert southwest region of Arizona. The mean temperature of soil at this depth during these trials ranged from 37 to 39°C. Furthermore, in two of these trials, after summer dry fallow periods of 38 and 45 days, the pathogen could not be detected at a depth of 15 to 20 cm and was detected in only one of 19 soil samples at a depth of 25 to 30 cm. In comparison, the pathogen was recovered from a high proportion of soil samples subjected to a dry winter fallow period or maintained in the greenhouse and planted with a seedling of citrus, alfalfa, or irrigated without the presence of any plant, where mean temperature of soil ranged from 15 to 30°C. In regions with a hot and dry summer climate, a dry summer fallow treatment of soil after removal of an existing citrus planting and before establishment of a new grove could provide a rapid and relatively inexpensive means of lowering the population of P. nicotianae to virtually nondetectable levels to at least a depth of 30 cm. © 2009 The American Phytopathological Society.
• Chitrampalam, P., Figuli, P. J., Matheron, M. E., Subbarao, K. V., & Pryor, B. M. (2008). Biocontrol of lettuce drop caused by Sclerotinia sclerotiorum and S. minor in desert agroecosystems. Plant Disease, 92(12), 1625-1634.
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  Abstract: Field experiments were conducted over 2 years in Yuma County, AZ, and Imperial County, CA, to determine the efficacy of several biocontrol agents for the management of lettuce drop caused by Sclerotinia spp. Commercial formulations of Trichoderma harzianum (Plantshield, Supersivit), Gliocladium virens (Soilgard), Coniothyrium minitans (Contans), and Bacillus subtilis (Companion) were evaluated and compared with the chemical fungicide iprodione (Rovral) against Sclerotinia sclerotiorum and S. minor. A single application of biocontrol products or of Rovral did not reduce lettuce drop caused by either Sclerotinia species. However, two applications of Contans, one at planting and one at post-thinning, significantly reduced the incidence of lettuce drop caused by S. sclerotiorum and increased yield but had no effect on S. minor at both locations in both years. Two applications of other biocontrol products did not significantly reduce disease incidence despite medium to high recovery following application. In contrast, Contans was only sporadically recovered following application. In vitro fungicide sensitivity evaluation revealed that both Trichoderma and Gliocladium species were tolerant to iprodione, dicloran (Botran), and vinclozolin (Ronilan) up to 1,000 ppm a.i., whereas both Sclerotinia spp. and C. minitans were sensitive to all three fungicides above 1 ppm. In summary, Contans was the most effective treatment for the control of lettuce drop caused by S. sclerotiorum, but no treatment was effective against S. minor in the desert lettuce production systems. © 2008 The American Phytopathological Society.
• Matheron, M. E., & Porchas, M. (2007). Comparative performance and preservation of chemical management tools for powdery mildew on muskmelon. Acta Horticulturae, 731, 357-361.
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  Abstract: Over 6, 000 ha of muskmelons (Cucumis melo) are currently grown in the State of Arizona in the United States. Powdery mildew, caused by the fungus Podosphaera xanthii (formerly known as Sphaerotheca fuliginea) is an annual concern for growers in this arid region. The efficacy of several fungicides, applied alone, in mixtures or in a rotational program, was evaluated for control of powdery mildew on muskmelon. The role of selected adjuvants in management of the disease also was examined. All treatments in 2002 through 2004 field trials significantly reduced the severity of powdery mildew on muskmelon compared to nontreated plots. Of the chemistries evaluated, triflumizole and wettable sulfur were among the most effective fungicides in all three trials, reducing the severity of powdery mildew from 72 to 100% and 69 to 89%, respectively, compared to nontreated plants. Quinoxyfen was among the best performers in two trials, suppressing disease 86 and 100%. Reduction of powdery mildew severity by at least 70% in at least one trial also was achieved by azoxystrobin, chlorothalonil, myclobutanil, potassium bicarbonate, pyraclostrobin, thiophanatemethyl and trifloxystrobin. Disease control by mixtures of fungicides was equivalent to and sometimes significantly better than the performance of individual components of the mixture. Similarly, the rotational programs provided levels of disease control equivalent to and in one instance significantly better than the performance of each component of the rotational program. These rotational programs included pyraclostrobin alternated with triflumizole, quinoxyfen alternated with thiophanate-methyl, thiophanate- methyl alternated with pyraclostrobin, trifloxystrobin alternated with chlorothalonil, trifloxystrobin alternated with quinoxyfen, and triflumizole alternated with quinoxyfen. Adjuvants are often added to a fungicide spray mixture to improve the performance of the fungicide. Three adjuvants, Kinetic, No Foam A and Silwet L-77 significantly reduced the severity of powdery mildew on muskmelon when applied without a partner fungicide.
• Matheron, M. E., Porchas, M., & Bigelow, D. M. (2006). Factors affecting the development of wood rot on lemon trees infected with Antrodia sinuosa, Coniophora eremophila, and a Nodulisporium sp. Plant Disease, 90(5), 554-558.
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  Abstract: Brown heartwood rot, which often is found in branches within lemon groves in southwestern Arizona, is caused by two basidiomycete fungi, Antrodia sinuosa and Coniophora eremophila. Another fungus, a species of Nodulisporium, has been recovered from small, dying lemon tree branches with an internal white wood rot. Studies were conducted from 1999 through 2002 to compare the extent of wood decay caused by these fungi (i) on lemon tree branches at different times of the year, (ii) on different types of citrus, (iii) on some desert woody perennial plants, and (iv) on lemon tree branches treated with selected fungicides. The mean length of wood decay columns recorded in lemon tree branches inoculated with A. sinuosa, C. eremophila, and the Nodulisporium sp. during the time periods of November to January, February to April, May to July, and August to October was 2.9,4.7, 13.3, and 15.2 cm, respectively. There was a significant linear correlation between the length of wood decay columns and air temperature for all three pathogens. The mean length of wood decay columns for all time periods in branches inoculated with A. sinuosa, C. eremophila, and the Nodulisporium sp. was 11.8, 5.8, and 9.6 cm, respectively. In two trials, wood decay columns were significantly greater on Lisbon lemon tree branches inoculated with A. sinuosa compared with those on Marsh grapefruit and Valencia orange trees inoculated with the same pathogen. Wood decay in the presence of the Nodulisporium sp. was greater on branches of lemon compared with grapefruit trees in two trials and on lemon compared with orange trees in one of two trials. With the exception of C. eremophila on creosote bush, each of the three wood rot pathogens caused some wood decay in branches of velvet mesquite, salt cedar, Mexican palo verde, and creosote bush, four common desert perennials found in southwestern Arizona. Compared with nontreated but inoculated lemon trees, the length of wood decay columns in branches inoculated with A. sinuosa, C. eremophila, and the Nodulisporium sp. in the presence of propiconazole was reduced by 79, 94, and 92%, respectively, and, in the presence of azoxystrobin, was suppressed by 71, 80, and 89%, respectively. Current management guidelines focus on minimizing branch fractures and other nonpruning wounds in conjunction with early detection and removal of infected branches before the onset of the increased wood decay development period extending from May to October. © 2006 The American Phytopathological Society.
• Matheron, M. E., & Porchas, M. (2005). Influence of soil temperature and moisture on eruptive germination and viability of sclerotia of Sclerotinia minor and S. sclerotiorum. Plant Disease, 89(1), 50-54.
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  Abstract: The effect of soil temperature and moisture on eruptive germination and viability of sclerotia of Sclerotinia minor and S. sclerotiorum in field soil was examined. In two trials at constant temperatures, the proportion of sclerotia of both pathogens that germinated in wet soil (≥-0.02 MPa) tended to decrease as soil temperature increased from 15 to 40°C, with no germination of sclerotia of S. minor and S. sclerotiorum detected after 1 and 2 weeks, respectively, at 40°C. In contrast, after 1 to 4 weeks in dry soil (≤-100 MPa) at 40°C, germination of sclerotia of S. minor and S. sclerotiorum ranged from 28 to 55% and 42 to 77%, respectively. In field trials, the germination rate of sclerotia of S. minor and S. sclerotiorum after 2 to 8 weeks in irrigated soil on the surface or buried at a depth of 5 cm was significantly lower than that for sclerotia maintained in dry soil at the same depths. On the other hand, after burial at a depth of 10 cm, germination of sclerotia in irrigated and dry soil did not differ significantly after 2 to 8 weeks for S. minor and after 2, 4, and 8 weeks for S. sclerotiorum. For both pathogens, germination of sclerotia from 2 to 8 weeks in irrigated soil with a mean temperature of 32°C was significantly lower than that for sclerotia in irrigated soil with a mean temperature of 26°C. In microplot trials conducted in July and August, no sclerotia of S. minor and S. sclerotiorum germinated after 2 and 3 weeks, respectively, after recovery from flooded soil with mean soil temperatures ranging from 30 to 33°C. A flood irrigation is often applied to fields for salt management during July or August in the Yuma lettuce production region. Results from these studies suggest that maintaining this flooding event for 2 to 3 weeks in fields with a history of lettuce drop caused by S. minor and S. sclerotiorum could significantly reduce the population of viable sclerotia.
• Matheron, M. E., McCreight, J. D., Tickes, B. R., & Porchas, M. (2005). Effect of planting date, cultivar, and stage of plant development on incidence of fusarium wilt of lettuce in desert production fields. Plant Disease, 89(6), 565-570.
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  Abstract: Fusarium wilt of lettuce, first recognized in Japan in 1955, has since been discovered in the United States (California in 1990, Arizona in 2001), Iran (1995), Taiwan (1998), and Italy (2001). In Arizona, the causal agent, Fusarium oxysporum f. sp. lactucae, has been recovered from lettuce plants in 27 different lettuce fields during the 2001 to 2003 production seasons. Studies were initiated to examine the impact of planting date, cultivar, and stage of plant development on the incidence of disease in the field. In 2002 and 2003, tested lettuce cultivars were sown in at least one of the following planting windows; early-season (September), mid-season (October), and late-season (December). Within each planting window, significant differences in disease incidence among lettuce cultivars were noted at plant maturity. The mean incidence of Fusarium wilt on cultivars sown in September, October, and December was 92.3, 15.1. and 2.0%, respectively, in 2002 and 74.2, 5.1, and 0.7%, respectively, in 2003. The mean soil temperatures at the 10-cm depth during the September, October, and December plantings for both years were 26, 14, and 14°C, respectively. Initial symptoms of Fusarium wilt were apparent as early as 14 days after seeding, with increasing incidence of disease noted as the crop developed and reached maturity. Among all lettuce cultivars planted in September, only one and two cultivars of romaine in 2002 and 2003, respectively, reached maturity with ≤5% incidence of Fusarium wilt, whereas the lowest incidence of disease among crisphead, green leaf, red leaf, or butterhead cultivars was 73.7, 27.0, 20.2, and 65.7%, respectively, in 2002 and 62.1, 29.0, 100, and 100%, respectively, in 2003. For October plantings, all romaine cultivars had ≤5% incidence of Fusarium wilt at maturity, whereas disease incidence among tested cultivars of crisphead lettuce in 2002 and 2003 ranged from 0.8 to 66.8% and 0.3 to 43.3%, respectively. When planted in December, 82 and 88% of tested cultivars, including all romaine entries, reached maturity with ≤1% incidence of Fusarium wilt. Selection of appropriate lettuce cultivars and planting times should allow successful production of lettuce in the southwestern Arizona production region with minimal or no incidence of disease in fields infested with F. oxysporum f. sp. lactucae. On the other hand, successful production of lettuce in infested fields when temperatures favor disease development will not be possible until lettuce cultivars are developed that possess high tolerance or resistance to the pathogen. © 2005 The American Phytopathological Society.
• McCreight, J. D., Matheron, M. E., Tickes, B. R., & Platts, B. (2005). Fusarium wilt race 1 on lettuce. HortScience, 40(3), 529-531.
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  Abstract: Three races of Fusarium oxysporum f.sp. lactucae, cause of fusarium wilt of lettuce, are known in Japan, where the pathogen was first observed in 1955. Fusarium wilt first affected commercial U.S. lettuce production in 1990 in Huron, Calif., but did not become a serious problem in the U.S. until 2001 when it reappeared in Huron and appeared in the Yuma, Arizona lettuce production area. Reactions of three fusarium wilt differentials ('Patriot', susceptible to races 1,2 and 3; 'Costa Rica No. 4', resistant to race 1, and susceptible to races 2 and 3; and 'Banchu Red Fire', susceptible to races 1 and 3, and resistant to race 2) in a naturally-infected commercial field test and artificially-inoculated greenhouse tests, indicated presence of race 1 in the Yuma lettuce production area. Reactions of these differentials to an isolate from Huron confirmed the presence of race 1 in that area. Consistent with previous results from the U.S. and Japan, 'Salinas' and 'Salinas 88' were resistant to the Yuma and Huron isolates of race 1, whereas 'Vanguard' was highly susceptible. Limited F1 and F2 data indicate that resistance to race 1 in 'Costa Rica No. 4' and 'Salinas' is recessive. 'Calmar' is the likely source of resistance in 'Salinas' and 'Salinas 88'.
• Matheron, M. E., & Porchas, M. (2004). Activity of boscalid, fenhexamid, fluazinam, fludioxonil, and vinclozolin on growth of sclerotinia minor and s. sclerotiorum and development of lettuce drop. Plant Disease, 88(6), 665-668.
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  Abstract: Sclerotinia drop is a major disease of lettuce caused by two soilborne fungi, Sclerotinia minor and S. sclerotiorum. Fungicides such as dicloran (Botran), iprodione (Rovral), and vinclozolin (Ronilan) are currently available in the United States to manage this disease. Studies were conducted to investigate the relative effect of some new fungicides, including boscalid, fenhexamid, fluazinam, and fludioxonil, in comparison with vinclozolin, on growth of S. minor and S. sclerotiorum in agar plate tests as well as control of lettuce drop in the field. At a rate of 0.001 μg/ml, all tested compounds only suppressed mycelial growth of either pathogen from 0 to 20%. At 0.01 μg/ml, mycelial growth of S. minor was reduced 82 to 84% by fludioxonil and fluazinam and only 1 to 16% by boscalid, fenhexamid, and vinclozolin. At the same rate, mycelial growth of S. sclerotiorum was reduced 78% by fluazinam and from 0 to 12% by boscalid, fludioxonil, fenhexamid, and vinclozolin. At 0.1 μg/ml, all tested chemistries except vinclozolin inhibited mycelial growth of S. minor from 70 to 98%, whereas growth of S. sclerotiorum was suppressed 95 to 99% by fludioxonil and fluazinam, significantly less (40 to 47%) by boscalid and fenhexamid, and not at all by vinclozolin. At a rate of 1.0 μg/ml, all tested fungicides reduced mycelial growth of S. minor and S. sclerotiorum from 87 to 100% and 77 to 100%, respectively. Mycelial growth emerging from sclerotia of S. minor was reduced from 98 to 100% by all fungicides tested at a rate of 1.0 μg/ml, whereas growth from sclerotia of S. sclerotiorum was suppressed from 90 to 96% by fenhexamid, fludioxonil, fluazinam, and vinclozolin. In lettuce plots infested with S. minor, boscalid and fluazinam provided the highest level of disease control, significantly greater than that achieved with fenhexamid, fludioxonil, and vinclozolin. In the presence of S. sclerotiorum, the highest degree of disease suppression occurred with application of fluazinam, fludioxonil, and vinclozolin, whereas the least effective compound was fenhexamid. Boscalid and fluazinam were more effective against lettuce drop caused by S. minor than disease caused by S. sclerotiorum.
• Matheron, M. E., & Porchas, M. (2002). Comparative ability of six fungicides to inhibit development of Phytophthora gummosis on citrus. Plant Disease, 86(6), 687-690.
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  Abstract: The activity of the registered fungicides fosetyl-A1 and metalaxyl (subsequently replaced with mefenoxam by the manufacturer) was compared with other potentially useful compounds, azoxystrobin, dimethomorph, fluazinam, and zoxamide, for suppression of canker development on citrus bark after inoculation with Phytophthora citrophthora or P nicotianae. The number of sweet orange trees on which cankers developed after inoculation with P citrophthora and the average size of cankers when present were lower on plants treated with dimethomorph, fosetyl-Al, or metalaxyl compared with nontreated trees and those treated with azoxystrobin or fluazinam. When bark removed from treated trees was inoculated with P citrophthora on the cambium surface at 5, 30, or 60 days after treatment (DAT), inhibition of lesion development on bark strips treated with dimethomorph, fosetyl-Al, or metalaxyl was significantly greater than that detected on bark treated with azoxystrobin, fluazinam, or zoxamide. When inoculated with P nicotianae at 5 or 30 DAT, reduction of lesion size on bark strips treated with dimethomorph, fosetyl-Al, or metalaxyl was significantly greater than that detected on bark treated with azoxystrobin or fluazinam. Inhibition of lesion development by zoxamide was significantly less than that observed with metalaxyl at 5 DAT on bark inoculated with P nicotianae; however, at 30, 60, and 90 DAT there was no significant difference in the performance of either fungicide. Reduction of lesion growth on the cambium surface compared with outer bark surface, when inoculated with P citrophthora, did not differ significantly from 5 to 30 DAT for bark tissue treated with azoxystrobin, dimethomorph, fosetyl-Al, or metalaxyl. Among the nonregistered fungicides tested, dimethomorph provided the best level of Phytophthora gummosis control on citrus.
• Matheron, M. E., & Porchas, M. (2002). Suppression of Phytophthora root and crown rot on pepper plants treated with Acibenzolar-S-Methyl. Plant Disease, 86(3), 292-297.
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  Abstract: The fungicide mefenoxam is registered for the control of Phytophthora blight of peppers caused by Phytophthora capsici. Isolates of the pathogen that are insensitive to mefenoxam, however, have been detected in some locations. Consequently, alternative methods are needed to control Phytophthora blight of peppers. Acibenzolar-S-methyl (ABM, Actigard) is a chemical activator of plant disease resistance that has potential for the management of Phytophthora blight of peppers. The effect of foliar applications of ABM on the development of root and crown rot on pepper plants grown in the greenhouse and inoculated with Phytophthora capsici or in soil naturally infested with the pathogen was evaluated. Inhibition of stem canker development on pepper cvs. Bell Tower and AZ9 after four treatments with ABM (75 μg/ml) was significantly greater than on plants receiving a single application of the chemical. Stem canker length on Bell Tower or AZ9 peppers was inhibited by 93.2 to 97.2% and 87.4 to 92.4% when plants were inoculated with P. capsici at 1 or 5 weeks, respectively, after the fourth application of ABM. Survival of chile pepper plants grown in field soil naturally infested with P. capsici was significantly increased by three foliar applications of ABM (75 μg/ml) compared with nontreated plants in all three trials when pots were watered daily and in two of three trials when pots were flooded for 48 h every 2 weeks. When soil was flooded every 2 weeks to establish conditions highly favorable for disease development, plants treated once with mefenoxam (100 μg/ml) survived significantly longer than those treated with ABM. On the other hand, when water was provided daily without periodic flooding to establish conditions less favorable for disease development, plant survival between the two chemicals was not different in two of three trials. Length of survival among chile pepper plants treated twice with 25, 50, or 75 μg/ml of ABM and grown in soil infested with P. capsici was not different. This work indicates that ABM could be an important management tool for Phytophthora root and crown rot on pepper plants.
• Holbrook, C. C., Wilson, D. M., Matheron, M. E., Hunter, J. E., Knauft, D. A., & Gorbet, D. W. (2000). Aspergillus colonization and aflatoxin contamination in peanut genotypes with reduced linoleic acid composition. Plant Disease, 84(2), 148-150.
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  Abstract: Aspergillus flavus and A. parasiticus can contaminate several agricultural crops with the toxic fungal metabolite aflatoxin. Previous research has indicated that resistance may be conferred by altering the fatty acid composition of these crops. Recently, peanut breeding lines with reduced linoleic acid content have been developed. The purpose of this study was to examine the effect of reduced linoleic acid composition on preharvest aflatoxin contamination of peanut. Seven breeding lines with relatively low linoleic acid and two check genotypes were grown in a randomized complete block design with 10 replicates for 4 years in Georgia and for 3 years in Arizona. The plots were inoculated with a mixture of A. flavus and A. parasiticus about 60 days after planting and subjected to drought and heat stress for the 40 days immediately preceding harvest. Differences were observed in only one environment. Low linoleic acid composition had no measurable effect on preharvest aflatoxin contamination in peanut when data were combined across years and locations. Products of the lipoxygenase pathway that have been shown to affect aflatoxin biosynthesis in vitro may not be present in sufficient quantities in peanut.
• Matheron, M. E., & Porchas, M. (2000). Comparison of five fungicides on development of root, crown, and fruit rot of chile pepper and recovery of Phytophthora capsici from soil. Plant Disease, 84(9), 1038-1043.
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  Abstract: The activity of five fungicides, azoxystrobin, dimethomorph, fluazinam, fosetyl-Al, and metalaxyl (subsequently replaced with mefenoxam by the manufacturer), was compared for effects on the development of root, crown, and fruit rot of chile pepper and on recovery of Phytophthora capsici from naturally infested soil. When inoculated with zoospores, plants survived longer and shoot and root fresh weights were greater for plants drenched with metalaxyl at 10 μg/ml than for plants treated with the same rate of azoxystrobin or dimethomorph. At 100 μg/ml, the duration of plant survival was greater for dimethomorph and fluazinam than for azoxystrobin; however, shoot and root growth did not differ. In soil naturally infested with P. capsici, survival and growth of shoots and roots for plants treated with dimethomorph at 100 μg/ml were greater than for those treated with the same rate of azoxystrobin or fluazinam. The most effective compounds for inhibition of lesion development on stems and fruit were mefenoxam at 1,200 μg/ml and dimethomorph at 480 μg/ml. Recovery of P. capsici from soil treated with each of the five tested compounds was significantly less than that recorded for soil not receiving a fungicide. The potential and relative value of azoxystrobin, dimethomorph, fosetyl-Al, and fluazinam as chemical management tools for Phytophthora blight on chile pepper, in addition to metalaxyl (replaced with mefenoxam), has been demonstrated.
• Matheron, M. E., & Porchas, M. (2000). Impact of azoxystrobin, dimethomorph, fluazinam, fosetyl-Al, and metalaxyl on growth, sporulation, and zoospore cyst germination of three Phytophthora spp.. Plant Disease, 84(4), 454-458.
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  Abstract: In vitro activity of azoxystrobin, dimethomorph, and fluazinam on growth, sporulation, and zoospore cyst germination of Phytophthora capsici, P. citrophthora, and P. parasitica was compared to that of fosetyl-Al and metalaxyl. The 50% effective concentration (EC50) values for inhibition of mycelial growth of the three pathogens usually were lowest for dimethomorph and metalaxyl, ranging from 3,000 μg/ml. Reduction of sporangium formation by P. capsici, P. citrophthora, and P. parasitica in the presence of dimethomorph at 1 μg/ml was significantly greater than that recorded for the same concentration of azoxystrobin, fluazinam, and fosetyl-Al. For the three species of Phytophthora, zoospore motility was most sensitive to fluazinam (EC50 and EC90 values of 1,000 μg/ml, respectively) and metalaxyl (EC50 and EC90 from 32 to 280 and 49 to 529 μg/ml, respectively), and lowest in sensitivity to azoxystrobin and fosetyl-Al (EC50 and EC90 from 256 to >1,000 μg/ml). The activity of azoxystrobin, dimethomorph, and fluazinam on one or more stages of the life cycle of P. capsici, P. citrophthora, and P. parasitica suggests that these compounds potentially could provide Phytophthora spp. disease control comparable to that of the established fungicides fosetyl-Al and metalaxyl.
• Bigelow, D. M., Gilbertson, R. L., & Matheron, M. E. (1998). Cultural studies of fungi causing brown rot in heartwood of living lemon trees in Arizona. Mycological Research, 102(3), 257-262.
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  Abstract: Coniophora eremophila and Antrodia sinuosa cause brown heartrot in living lemon trees in southern Arizona and California. They can be distinguished in the field by differences in rot characteristics. Both have a high optimum growth temperature of approximately 35 °C. Coniophora eremophila has a cultural morphology typical of other Coniophora species and did not fruit in culture. Antrodia sinuosa cultures were morphologically similar to previous reports and fruited readily under laboratory conditions. Mating tests with homokaryotic single spore isolates showed it to have a heterothallic bipolar mating system. The decay capacity of C. eremophila on lemon wood test blocks under laboratory conditions was low compared to that of A. sinuosa, five other brown rot fungi, and three white rot fungi.
• Matheron, M. E., & Call, R. E. (1998). Factors affecting the development and management of Septoria leaf spot of pistachio in Arizona. Acta Horticulturae, 470, 592-595.
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  Abstract: In 1964, Septoria leaf spot was detected for the first time in the United States in experimental pistachio (Pistacia vera) plantings at Brownwood, Texas. A moderate level of the same disease, caused by the fungus Septoria pistaciarum, was first observed in 1986 on leaves of pistachio trees in Arizona. In 1988 a survey of the 800 ha of pistachio orchards in southeastern Arizona revealed a widespread incidence of the disease. Since the initial discovery and identification of the disease, Septoria leaf spot has appeared every year in Arizona pistachio orchards. The onset and severity of the disease is affected by summer rainfall that occurs in this region. Yearly disease management studies conducted since 1992 have shown that as few as two applications of chlorothalonil in July and August can virtually prevent disease development. Applications of copper hydroxide or benomyl alone or in combination also effectively arrested disease development. Leaves around nut clusters not receiving fungicide treatments were senescent at crop maturity, while leaves on treated trees showed no sign of senescence. Pistachio trees infected with Septoria leaf spot and not treated with a fungicide can defoliate in the autumn up to 2 months prematurely.
• Matheron, M. E., Wright, G. C., & Porchas, M. (1998). Resistance to Phytophthora citrophthora and P. parasitica and nursery characteristics of several citrus rootstocks. Plant Disease, 82(11), 1217-1225.
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  Abstract: Studies were conducted to compare existing and potential citrus rootstocks with respect to resistance to root rot and gummosis caused by Phytophthora citrophthora and P. parasitica in greenhouse and growth chamber experiments and horticultural performance under simulated nursery conditions. Depending upon rootstock and experiment, mean root weights resulting from inoculation with P. citrophthora were 27 to 96% lower than the comparable controls. In similar experiments with the same rootstocks, inoculation with P. parasitica resulted in root weights that were 38 to 95% less than weights of the noninoculated controls. During 1994 or 1995, mean root weight reduction compared with noninoculated plants among Citrus macrophylla, rough lemon, C. volkameriana, and Sunki mandarin x Flying Dragon trifoliate (62-10919) attributable to P. citrophthora and mean root weight reduction among C. macrophylla, C. volkameriana, rough lemon, Sacaton citrumelo, Sunki mandarin x Flying Dragon trifoliate (62109-19), African shaddock x Rubidoux trifoliate, and Shekwasha mandarin x English trifoliate attributable to P. parasitica were significantly less than those recorded for all other tested rootstocks. Rootstocks that sustained a low percentage of root weight reduction generally experienced a low percentage of shoot weight reduction and survived longer as well. In evaluation of resistance to gummosis, depending on rootstock and experiment, the mean length of stem lesions caused by P. citrophthora on rootstocks ranged from 0.2 to 25.0 mm, whereas values for P. parasitica ranged from 0.2 to 18.5 mm. Stem lesions smaller than 5 mm in length were recorded for 21 and 14 of 36 different rootstocks inoculated with P. citrophthora and P. parasitica, respectively. On the other hand, P. citrophthora and P. parasitica caused stem lesions of at least 10 mm in length on 8 and 16 citrus rootstocks, respectively. Desirable nursery characteristics, including vigorous growth, minimal branching, and high leaf chlorophyll content, were demonstrated most prominently by Gomiri rough lemon, C. volkameriana, and Benton citrange, and to a lesser degree by some other rootstocks. Possible factors that could account for inconsistent classification of some citrus rootstocks as susceptible or resistant to Phytophthora root rot and gummosis are discussed.
• Holbrook, C. C., Wilson, D. M., Matheron, M. E., & Anderson, W. F. (1997). Aspergillus colonization and aflatoxin contamination in peanut genotypes with resistance to other fungal pathogens. Plant Disease, 81(12), 1429-1431.
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  Abstract: Indirect selection tools would be valuable in the development of peanut (Arachis hypogaea) cultivars with resistance to aflatoxin contamination. The objective of this study was to determine whether resistance to other fungi could be used as an indirect selection tool for resistance to colonization of peanut by Aspergillus flavus group fungi or aflatoxin contamination. Nine peanut genotypes with resistance to late leaf spot (Cercosporidium personatum) or white mold (Sclerotium rolfsii) were evaluated for 2 years at Tifton, GA, and Yuma, AZ. Plots were subjected to late-season heat and drought stress. None of the genotypes exhibited less colonization of shells or kernels by A. flavus group fungi than cv. Florunner when tested in Georgia or Arizona. None of the genotypes showed a reduced level of aflatoxin contamination in comparison to Florunner at either location. These results indicate that the mechanisms of resistance to other fungi operating in these genotypes are not effective in providing resistance to colonization by A. flavus group fungi or reducing aflatoxin contamination. Therefore, resistance to these fungi cannot be used as an indirect selection tool for resistance to aflatoxin contamination.
• Matheron, M. E., Porchas, M., & Matejka, J. C. (1997). Distribution and seasonal population dynamics of Phytophthora citrophthora and P. parasitica in Arizona citrus orchards and effect of fungicides on tree health. Plant Disease, 81(12), 1384-1390.
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  Abstract: The distribution and seasonal population dynamics of Phytophthora citrophthora and P. parasitica within citrus orchards in southwestern and central Arizona were determined over a multiple-year period. In central Arizona, P. citrophthora alone, P. parasitica alone, or both pathogens together were recovered from 7, 37, and 41% of sampled orchards, respectively, whereas in the southwestern production area, the same pathogens alone or in combination were recovered from 17, 50, and 17% of sampled orchards, respectively. For a 6-year period, the average population density of P. parasitica in southwestern Arizona was 16.7 propagules/g of dry soil. For 2 of 3 years, the population density of P. citrophthora at the 10-cm soil depth was significantly higher in the spring than in the preceding winter or the following autumn season. There were no significant seasonal multiple-year differences in population levels of P. parasitica. Propagule densities of both pathogens, as well as root densities, generally decreased as soil depth increased from 10 to 60 cm. No consistent significant correlation was detected between propagule density of either pathogen and soil temperature or soil moisture at the time of collection. A multiple-year treatment program with fosetyl-Al or metalaxyl resulted in significantly healthier tree canopies and higher root densities compared to nontreated trees; however, population densities of P. citrophthora and P. parasitica did not differ significantly when nontreated trees were compared to those receiving fungicide treatments.
• Bigelow, D. M., Matheron, M. E., & Gilbertson, R. L. (1996). Biology and control of Coniophora eremophila on lemon trees in Arizona. Plant Disease, 80(8), 934-939.
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  Abstract: A survey of mature lemon trees showed an average of 30% of trees with symptoms of brown heartrot caused by Coniophora eremophila. Growth of C. eremophila inoculated into branches of Valencia orange, Marsh grapefruit, Orlando tangelo, or Lisbon lemon on rough lemon rootstock was significantly higher in lemon than in other types of citrus. C. eremophila inoculated into Lisbon lemon branches on trees established on rough lemon, volkameriana, macrophylla, Cleopatra mandarin, sour orange, or Troyer citrange rootstocks showed no significant differences in growth. Somatic incompatibility tests of isolates from one mature orchard demonstrated that isolates from different trees were incompatible. In vitro fungicide trials showed that NECTEC P paste and NECTEC blank paste effectively reduced decay on lemon blocks 15 weeks after inoculation with C. eremophila. Field fungicide trials showed that NECTEC P paste with fungicides, as well as the blank paste without fungicides, significantly inhibited the advance of the fungus 7 months after inoculation. Also, propiconazole at 10,000 μg/ml, imazalil at 20,000 μg/ml, or propiconazole at 10,000 μg/ml in combination with imazalil at 20,000 μg/ml significantly inhibited the advance of the fungus.
• Matheron, M. E., & Porchas, M. (1996). Colonization of citrus roots by Phytophthora citrophthora and P. parasitica in daily soil temperature fluctuations between favorable and inhibitory levels. Plant Disease, 80(10), 1135-1140.
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  Abstract: Studies compared colonization of citrus rootlets by Phytophthora citrophthora or P. parasitica under constant favorable or inhibitory temperatures to root colonization under various daily combinations of favorable and inhibitory temperatures. Colonization of rough lemon rootlets after incubation for 96 h in the presence of soil naturally infested with P. citrophthora was detected at 9 through 27°C; however, the extent of colonization detected at 27°C was significantly lower than that observed at the other temperatures. In comparison, colonization of rootlets in the presence of soil naturally infested with P. parasitica was detected at constant incubation temperatures ranging from 12 to 33°C; however, the extent of colonization at 33°C was significantly lower than that observed at the other temperatures. Critical threshold temperatures, defined as thermal values at or above which colonization of rootlets was significantly restricted or prevented, were 27°C for P. citrophthora and 33°C for P. parasitica. After four consecutive 24-h periods, the magnitude of rootlet colonization by both pathogens was significantly less under incubation that included a daily time of at least 2.5 h at or above the threshold temperature when compared to rootlet colonization for 96 h at a constant favorable temperature. Significantly fewer sporangia were produced by P. citrophthora or P. parasitica at 24 h than after 48 and 72 h. The extent of root infection caused by P. citrophthora and P. parasitica at 24 or 30°C, respectively, was significantly lower at incubation periods of 4, 8, and 16 h than at periods of 24, 48, and 72 h. A fivefold increase in duration of zoospore motility was observed for P. citrophthora at 24°C than at 30°C, temperatures that respectively favor and prevent rootlet colonization; while an 11-fold increase was detected for zoospores of P. parasitica at favorable compared to inhibitory temperatures of 30 and 36°C, respectively. Temperature periods partially as well as entirely at or above the critical threshold values may reduce the degree of citrus rootlet colonization by P. citrophthora and P. parasitica by retarding the rate of sporangium formation and zoospore production and the duration of zoospore motility, compared to periods of equal duration that are entirely favorable for rootlet colonization. More efficient use of fungicides for control of Phytophthora root rot of citrus could be possible by application only when soil temperatures favor disease development.
• Matheron, M. E., & Matejka, J. C. (1995). Comparative activities of sodium tetrathiocarbonate and metalaxyl on Phytophthora capsici and root and crown rot on chile pepper. Plant Disease, 79(1), 56-59.
• Matheron, M. E., & Matejka, J. C. (1993). Effect of sodium tetrathiocarbonate on growth and viability of Sclerotinia minor and S.sclerotiorum and development of lettuce drop. Plant Disease, 77(10), 995-998.

Proceedings Publications

• Liu, B., Feng, C., Matheron, M. E., & Correll, J. C. (2016, November). Web blight of spinach in the desert southwest caused by Pythium aphanidermatum. In 2016 International Spinach Conference.
• Matheron, M. E., & Porchas, M. (2016, November). Efficacy of fungicides for management of downy mildew of spinach. In 2016 International Spinach Conference.
• Wright, G. C., Matheron, M. E., & Porchas, M. (2016, November). Antrodia sinuosa - A wood rotting fungus that adversely affects lemons in Arizona. In 2016 International Citrus Congress.
• Matheron, M. E., & Porchas, M. (2015, Dec). Phytophthora, the Plant Destroyer: Past, Present, and Future. In 1st International Soilborne Oomycete Research and Education Conference.
• Matheron, M. E., & Porchas, M. (2015, Feb). Comparison of chemical management tools for spinach and lettuce downy mildew. In 2015 International Spinach Conference.
• Matheron, M. E., & Porchas, M. (2015, Nov). Fusarium wilt of lettuce: the Arizona story. In International Symposium on Fusarium Wilt of Lettuce.
• Matheron, M. E., & Porchas, M. (2015, Sept). Efficacy of conventional and biological fungicides for managing powdery mildew on two muskmelon varieties with different genetic susceptibility to the disease. In 2015 Australasian Plant Pathology Society Conference.
• Matheron, M. E., & Porchas, M. (2014, July). Relative ability of chemical management tools to inhibit stem lesion development on pepper plants inoculated with P. capsici. In 2014 American Phytopathological Society Annual Meeting.
• Matheron, M. E., & Porchas, M. (2014, Sept). Comparison of chemical, biological, and cultural tools to manage Sclerotinia drop of lettuce. In 8th Australasian Soilborne Diseases Symposium.
• Matheron, M., & Porchas, M. (2012, Fall). Strategies for managing Sclerotinia drop of lettuce. In 7th Australasian Soilborne Disease Symposium.
• Matheron, M., & Porchas, M. (2011, Fall). Effect of different biological and chemical tools as well as method and frequence of their application on management success of Phytophthora root and crown rot on peppers. In 3rd International Phytophthora capsici Conference.
• Matheron, M., & Porchas, M. (2011, Fall). Relative efficacy of chemical management tools on Phytophthora crown and root rot of pepper plants. In Phytopathology, 101.

Presentations

• Matheron, M. E. (2013, January through December). 11 oral presentations given and listed in the Cooperative Extension section of this report. Various state and national venues..

Poster Presentations

• Martin, P., Wright, G. C., Matheron, M. E., Matheron, M. E., Porchas, M., & Wright, G. C. (2016, September). ANTRODIA SINUOSA – A WOOD ROTTING FUNGUS THAT ADVERSELY AFFECTS LEMONS IN ARIZONA. International Society of Citriculture Conference. Foz do Iguassu, Brazil: International Society of Citriculture.

Creative Productions

• Matheron, M. E., & Bevington, R. (2017. Lettuce Downy Mildew. Yuma Center for Excellence in Desert Agriculture. Yuma: Yuma Center for Excellence in Desert Agriculture.
• Matheron, M. E., & Bevington, R. (2017. Lettuce Powdery Mildew. Yuma Center for Excellence in Desert Agriculture. Yuma: Yuma Center for Excellence in Desert Agriculture.

Others

• Matheron, M. E. (2018, January). 25 articles in the Arizona Vegetable IPM Newsletter. CALS Online Publication.
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  This newsletter is an online communication from The University of Arizona Vegetable Team, of which I am a member. At the end of 2018, there were over 903 individual clientele subscribers to this newsletter. Also, the updates are made available through the trade publication Western Farm Press.
• Matheron, M. E. (2017, January to December). 25 articles in Arizona Vegetable IPM Newsletter. CALS online publication.
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  25 articles were written for inclusion in the Arizona Vegetable IPM Updates Newsletter in 2017. This newsletter is an online communication from The University of Arizona Vegetable IPM Team, of which I am a member. At the end of 2017, there were over 860 individual clientele subscribers to this newsletter. Also, the updates are made available through the trade publication Western Farm Press.
• Matheron, M. E. (2016, January to December). 25 articles in Arizona Vegetable IPM Newsletter. CALS online publication.
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  25 articles were written for inclusion in the Arizona Vegetable IPM Updates Newsletter in 2016. This newsletter is an online communication from The University of Arizona Vegetable IPM Team, of which I am a member. At the end of 2016, there were 865 individual clientele subscribers to this newsletter. Also, the updates are made available through the trade publication Western Farm Press.
• Matheron, M. E. (2015, January to December). 25 articles in Arizona Vegetable IPM Newsletter. CALS online publication.
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  25 articles were written for inclusion in the Arizona Vegetable IPM Updates Newsletter in 2015. This newsletter is an online communication from The University of Arizona Vegetable IPM Team, of which I am a member. At the end of 2015, about 700 individual clientele subscribe to this newsletter. Also, the updates are made available through the trade publication Western Farm Press.
• Matheron, M. E. (2014, January to December). 25 articles in Arizona Vegetable IPM Newsletter. CALS online publication.
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  25 articles were written for inclusion in the Arizona Vegetable IPM Updates Newsletter in 2014. This newsletter is an online communication from The University of Arizona Vegetable IPM Team, of which I am a member. At the end of 2014, 575 individual clientele subscribe to this newsletter. Also, the updates are made available through the trade publication Western Farm Press.
• Matheron, M. E. (2013, January through December). Arizona Vegetable IPM Updates Newsletter.
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  25 articles were written for inclusion in the Arizona Vegetable IPM Updates Newsletter in 2013. This newsletter is an online communication from The University of Arizona Vegetable IPM Team, of which I am a member. At the end of 2013, 495 individual clientele subscribe to this newsletter. Also, the updates are made available through the trade publication Western Farm Press.
• Matheron, M. E. (2012, December). Arizona Vegetable IPM Updates Newsletter. Western Farm Press.
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  Exact Date: 12/29/2012
• Matheron, M., & Porchas, M. (2012, Fall). Assessment of fungicides for management of Sclerotinia lettuce drop, 2011. Plant Disease Management Reports.
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  Volume 6, Issue V077
• Matheron, M., & Porchas, M. (2012, Fall). Comparison of fungicides for management of powdery mildew on muskmelon, 2011. Plant Disease Management Reports.
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  Volume 6, Issue V075
• Matheron, M., & Porchas, M. (2012, Fall). Efficacy of fungicides for management of downy and powdery mildew on lettuce, 2011. Plant Disease Management Reports.
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  Volume 6, Issue v118
• Matheron, M., & Porchas, M. (2012, Fall). Evaluation of fungicides for management of the soil phase of Phytophthora blight. Plant Disease Management Reports.
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  Volume 6, Issue V119
• Matheron, M. E. (2011, December). Arizona Vegetable IPM Updates Newsletter. Western Farm Press.
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  Exact Date: 12/31/2011
• Matheron, M., & Porchas, M. (2011, Fall). Appraisal of fungicides for management of downy mildew on broccoli, 2010. Plant Disease Management Reports.
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  Volume 5, Issue V130
• Matheron, M., & Porchas, M. (2011, Fall). Assessment of fungicides for management of powdery mildew on muskmelon, 2010. Plant Disease Management Reports.
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  Volume 5, Issue V131
• Matheron, M., & Porchas, M. (2011, Fall). Comparison of fungicides for management of downy and powdery mildew on lettuce, 2010. Plant Disease Management Reports.
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  Volume 5, Issue V129
• Matheron, M., & Porchas, M. (2011, Fall). Efficacy of fungicides for management of Sclerotinia drop of lettuce, 2010. Plant Disease Management Reports.
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  Volume 5, Issue V132
• Matheron, M., & Porchas, M. (2011, Fall). Evaluation of biofungicide products for management of Sclerotinia drop of lettuce, 2010. Plant Disease Management Reports.
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  Volume 5, Issue V133
• Olsen, M., Matheron, M., McClure, M., & Xiong, Z. (2011, Fall). Diseases of Citrus in Arizona. Arizona Cooperative Extension.
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  AZ1154