I have some English yews that have been diagnosed with Phythopthera. I plan to remove them this spring and am looking for suggestions for an evergreen hedge that could be maintained at 6 to 8 feet. The plants obviously need to be resistant to Phythopthera. The area receives full to partial sun. I live in zone 6b. Any input would be appreciated.
Phythopthera spores can remain viable in the soil for many years. The fungus affects a number of woody plants, and it is possible for the disease to develop even in plants that are considered "resistant".
A list of plants that are thought to be resistant can be found at http://extension.psu.edu/plants/green-industry/files-pdfs/phytophthora-tolerant-plants
I am also attaching a list of susceptible plants that should be avoided.
Poor drainage and clay soils are commonly associated with this fungus. Avoid planting in poorly drained soil. If necessary, plant in raised beds or wide burms that are raised 6-8 inches above the surounding soil. At planting time, as well as annually thereafter, amend the soil with well-aged compost to improve drainage. However, avoid placing compost or mulch directly against the tree trunks. These should be kept at least 6 inches away from the bark.
One additional comment: the best defense against diseases is to maintain a variety of different plants. You might consider creating a deep border using several layers of foliage plants to add interest and diversity to your hedge.
I hope this information is helpful.