Arboriculture & Urban Forestry 40(6): November 2014 do the testing in-house (Agdia Inc. Elkhart, Indiana, U.S.). If tests are positive, chemical control methods can be used to help prevent loses. Fosetyl-Al, metalaxyl, phosphorous acid, and mefenoxam have been shown to be effective against P. cinnamomi on woody plants. Benson (1990) showed both fosetyl-Al and metalaxyl to be effective in controlling this dis- ease on Hinodegiri azaleas [Rhododendron obtusum (Lindl.) Planch] in containers and landscape beds. In the three-year study, there was no difference in growth between inoculated plants treated with either chemical compared to uninoculated control plants. Furthermore, the mortality rates of inocu- lated untreated plants were six times greater, and plants were less than half the size of those in all the other treatments. However, in all four treatments, rates of infection did increase over time. In a field study with Fraser fir [Abies fraseri (Pursh) Poir], application of fosetyl-Al (three times per growing season) or mefenoxam (two times per season) reduced mortality rates over a three-year period (Benson et al. 2006). Phytophthora cinnamomi is also a major pest on avocado, and fosetyl-Al or phosphorous acid have been shown to be the most effective among chemical controls (Gallo et al. 2007). Application of chemicals can be done to control the rate of infection or as a preventive measure. Pre- ventive treatment is recommended on important specimen trees and for plants subject to saturated soils since P. cinnamomi can progress rapidly from undetectable levels (Smiley et al. 1999). The first chemical application of the growing season should be done just before the fungus becomes active, which can be determined by monitoring soil temperatures. Smiley et al. (1999) indicates that infection is favored when the temperature of the soil exceeds 18°C, and Waterhouse (1963) indicates P. cinnamomi has an optimum growth temperature of 26°C. One to two repeat applications are recommended through the growing season and surrounding susceptible plants should be treated as well. An alternative to chemical control is the use of beneficial microorganisms. Zentmyer and Mircetich (1966) indicate antago- nistic soil microorganisms can reduce the presence and growth of pathogenic Phytophthora. How- ever, current research on this topic for landscape plants is limited and the effectiveness of applying beneficial microorganisms for disease manage- ment in the landscape is untested and unknown. 349 Water, disease, and nutrient management are pri- orities to ensure the longevity and health of Taxus in the landscape. When installing new plants, it is critical to select a site that is not prone to saturation and to determine if soil physical and chemical properties are appropriate. Monitoring plants through soil and tissue testing will help growers and gardeners make informed management decisions to protect plants from stress, which will ensure plants reach the max- imum potential and are impactful in the landscape. LITERATURE CITED Agrios, G. 1997. Plant Pathology, fourth edition. Academic Press, San Diego, California, U.S. pp. 270–274. Benson, D.M. 1986. Relationship of soil temperature and moisture to development of Phytophthora root rot of azalea. Plant Disease 69:1049–1054. Benson, D.M. 1990. Landscape survival of fungicide-treated aza- leas inoculated with Phytophthora cinnamomi. Plant Disease 74:635–637. Benson, D.M., J.R. Sidebottom, and J. Moody. 2006. Control of Phy- tophthora root rot in field plantings of Fraser fir with fosetyl-al and mefenoxam. Plant Management Network. Accessed 05/22/2014. Brady, N., and R. Weil. 2002. The Nature and Properties of Soils, 13th edition. Prentice Hall, Upper Saddle River, New Jersey, U.S. pp. 150. Crandall, B.S. 1936. Root disease of some conifers and hardwoods caused by Phytophthora cambivora (P. cinnamomi). The Plant Disease Reporter 20:202–204. Davis J., and D. Whiting. 2013. Choosing a soil amendment. Colo- rado State University Extension. Fact Sheet No. 7.235. Dumrose, R.K., and R.L. James. 2005. Root diseases in bareroot and container nurseries of the Pacific Northwest: Epidemiology, management, and effects on outplanting performance. New Forests 30:185–202. Ellis, M.A., S.A. Miller, and K.D. Cochran. 1993. First report of Phytophthora root rot caused by Phytophthora cinnamomi. Plant Disease 77:537. Fraedrich, B.R. 1999. Taxus disorders. Bartlett Tree Research Labo- ratories Technical Report. TR85:1–2. Gallo, L., F. Siverio, and A.M. Rodríguez-Pérez. 2007. Thermal sensitivity of Phytophthora cinnamomi and long-term effective- ness of soil solarisation to control avocado root rot. Annals of Applied Biology 150:65–73. Gilliam, C.H., J.T. Eason, and C.E. Evans. 1985. Effects of soil pH on four field-grown nursery crops. Journal of Environmental Horticulture 3:136–139. Halcomb, M. 2012. Taxus (Yew) field production. University of Ten- nessee Extension. Accessed 05/22/2014. Hibben, C.R., and A.W. Cahilly. 1996. Decline of Taxus in the New York Botanical Garden: Current status, contributing factors, and recommendations. New York Botanical Garden, New York City, New York, U.S. ©2014 International Society of Arboriculture
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