346 (Hibben and Cahilly 1996). From 1982 to 1992 at NYBG, a total of 28 Taxus began to decline and were removed from the grounds. A similar event also occurred at Arnold Arboretum in 1990. At both locations, Phytophthora cinnamomi Rands was iden- tified in the roots of the Taxus and was thought to be the causal agent. This rapid decline and loss of Taxus plants at two of America’s premier public gardens prompted a three and a half year study to deter- mine the possible cause. The experiment examined 71 specimens of Taxus at NYBG for needle loss, tip dieback, winter injury, needle distortion, branch dieback, arthropods, air pollution, disease, and plant nutrition. This extensive examination noted many types of stress that can affect the health of Taxus in the landscape. However, no definitive cause was determined nor were any strong trends associ- ated with needle chlorosis or poor plant health. Furthermore, symptoms of Phytophthora root rot were not discovered, even though specimens were still in decline during this period. One explanation for this was that during the 1982 to 1992 period, all susceptible specimens had been removed, and infection during the study was at a low level. The objective of this article is to review the lit- erature on Taxus cultural practices with a focus on water management, root rot caused by P. cinnamomi, and plant nutrition. Researchers hope to then use the information to develop best management prac- tices to maintain and possibly improve the health and longevity of mature Taxus in the landscape. WATER MANAGEMENT AND PHYTOPHTHORA CINNAMOMI Water management is considered the most critical fac- tor for the health of Taxus during production and in the landscape. The primary cause of death of plants in the landscape is high soil moisture, which is typically caused by poor soil drainage (Ellis et al. 1993; Fraed- rich 1999; Kaiser and Ward 2013). Saturated soils can cause anaerobic conditions in the root zone and starve respiring roots of oxygen. Furthermore, saturated soils create an environment ideal for Phytophthora sporangium production, zoospore release, and subse- quent root infection (Matheron and Mircetich 1985; Benson 1986; Agrios 1997; Dumrose and James 2005). In nearly every part of the world where soil becomes too wet for a particular plant, Phytophthora can cause damage in hosts ranging from vegetable seedlings ©2014 International Society of Arboriculture Taylor: Preventing Death and Taxus to mature woody plants (Agrios 1997). Once the fungus enters the root, it grows in the cambium and kills plants by debilitating water and nutrient uptake (Smiley et al. 1999). This can sometimes cause a very rapid decline in the aboveground portion of the plant. Young plants that are infected can die in just a few days, whereas older trees may take sev- eral months to years before they die. This depends on the environmental conditions and the amount of Phytophthora present in the soil (Agrios 1997). Root disease on Taxus caused by Phytophthora was first described by Crandall (1936). In particular, Crandall found P. cinnamomi on several species of Taxus in several eastern U.S. states. The first signs of the disease were described as the loss of green nee- dles and wilting of young shoots. However, Crandall did not link the occurrence of the disease with any particular environmental conditions. Schreiber and Green (1959) determined P. cinnamomi was causing the death of Taxus propagules, production liners, and older plants in the field. Symptoms were described as the gradual loss of mature green color, dieback, and occasional wilting of young shoots. The root systems also showed extensive discoloration of red- dish-brown to black. Authors also indicated disease incidence was most severe under conditions of high soil moisture or other environmental conditions detrimental to root development. Ellis et al. (1993) observed brick red lesions on roots of T. cuspidata and T. × media that were also showing the previously described above ground symptoms. Phytophthora cinnamomi was recovered from the roots and Koch’s postulates were used on two year old transplants of T. × media to determine this was the fungal agent causing dieback, root lesions, and reduced growth. In addition to soil moisture, soil temperature also has a significant effect on the pathogenesis of P. cinnamomi (Zentmyer 1981). Waterhouse (1963) indicated P. cinnamomi has an optimum growth temperature of 26°C. In a study with avocado, P. cinnamomi reduced growth when soil temperatures ranged from 15°C to 27°C with optimum infection rates occurring when temperatures were above 21°C (Zentmyer 1981). In a container study with azalea [Rhododendron obtusum (Lindl.) Planch.], root rot caused by P. cinnamomi was more severe when containers were exposed to sunlight, which could be due to higher soil temperatures (Benson 1986). These studies indicate temperature is a critical fac-
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