Arboriculture & Urban Forestry 40(6): November 2014 Arboriculture & Urban Forestry 2014. 40(6): 345–350 345 Preventing Death and Taxus: Review and Recommendations for Managing Taxus in the Landscape with Overview on Phytophthora cinnamomi, Soil, and Nutrition Status Matthew D. Taylor Abstract. At least three major gardens or arboreta in the USA have experienced periods of significant decline and death of mature Taxus (yews) in the landscape. The symptoms displayed on declining plants are described as chlorosis of the needles, partial defoliation, and death of some of the branches. Eventually, the entire plant may die, but they are typically removed before reaching this stage. Information on man- aging mature Taxus in the landscape is limited. The objective of this article is to review the literature on Taxus cultural practices and use the information to develop best management practices for Taxus in the landscape. Soil moisture is the most critical factor for health of plants in the landscape. Saturated soils create anaerobic conditions for roots and create an environment ideal for root infection by Phytophthora cinnamomi, the major root pathogen affecting Taxus. During planting, proper site selection and well-drained soil are crucial for the long- term survival of plants. Aſter planting, irrigation should be managed to avoid saturated soil. Management from a nutritional standpoint is poorly understood. Maintaining an appropriate pH of 6.0 to 7.0 and fertilizing plants based on soil and tissue testing is recommended. More research needs to be done to determine optimal fertilization rates and appropriate nutrient concentration in tissue and in soil. When plants become symptomatic, soil should be tested for P. cinnamomi. If the fungus is present, appropriate chemical controls should be used. Key Words. Manganese; Phytophthora cinnamomi; Plant Nutrition; Root Rot; Taxus; Water Management; Yew; Zinc. Taxus, or yews, are popular landscape plants due to their slow growth habit, dark evergreen foliage, pest resistance, and tolerance to sheering. At Long- wood Gardens in Kennett Square, Pennsylvania, U.S., Taxus are an integral component of the out- door displays. As of 2014, Longwood’s Taxus collection included 330 accessions composed primarily of three species: Taxus baccata, Taxus cus- pidata, and Taxus × media. More than half of the specimens in this collection are over 50 years old. Over the past several years many of the mature Taxus at Longwood Gardens have begun to show signs of decline at a rate that hadn’t been recog- nized in years prior. Since 2006, 78 Taxus accessions have been removed from the gardens. The rea- sons for removal may include: garden renovation, storm damage, disease, declining health, and death. Unfortunately, the definitive reason for removal of each of these accessions was not always deter- mined or recorded. Therefore, researchers cannot say for certain that there has been a higher inci- dence of decline or death of Taxus in the landscape at Longwood Gardens. The symptoms displayed on declining plants are described as chlorosis of the needles, partial defoliation, and death of some of the branches. Eventually, the entire specimen may die, but they are typically removed before reaching this stage. Upon removal and inspection of the roots, many of the plants exhibited blackening and rot- ting of the root system. This indicated Phytophthora infection, which was confirmed through serological tests on six of eight plants (University of Minne- sota, Plant Disease Clinic. St. Paul, Minnesota). At the New York Botanic Garden (NYBG) (Bronx, New York, U.S.) and the Arnold Arboretum (Boston, Massachusetts, U.S.), similar situations have occurred, where a significant number of Taxus specimens declined and/or died in the landscape ©2014 International Society of Arboriculture
November 2014
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