Management of Phytophthora Root Rot of Fraser Fir
Ornamentals Disease Information Note 1
R.K. Jones, Extension Plant Pathologist
Robert I. Bruck, Plant Pathologist




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Fraser Fir [Abies fraseri (Pursh) Poir] has developed into the premier Christmas tree species in western North Carolina. It is one of the most economically important species in our mountain counties. The root rot disease caused by Phytophthora cinnamomi is widespread and difficult to control in North Carolina. This disease has a wide range of hosts, including azalea, boxwood, rhododendron, dogwood, camellia, yew, cedar, mountain laurel, heather, juniper, blueberries, white pine and many other native and imported species. Historically, Phytophthora root rot has resulted in serious losses to trees in seed and line-out beds in North Carolina and is generally considered to be the most serious disease problem of Fraser fir. When summers are wet, soil conditions become very favorable for Phytophthora, which may result in serious local outbreaks of root rot in mature Christmas tree plantations. The causal organism is tenacious and may survive in infested soils for many years in its resistant form. When warm-wet conditions begin during the spring months, new infections may take place.

Shallow wet soils, underlying rock, compacted soil, setting trees deeper than the soil level in the nursery, overwatering plants, or long periods of heavy rains favor the development of this disease. When disease occurs under nursery or plantation conditions, management of root rot can be successfully accomplished by integrating silvicultural and chemical techniques. These techniques may be summarized as follows:

  1. Purchase disease-free seedlings and line-out plants from a reputable nursery. Avoid plants that lack normal green coloration, appear wilted, or plants that have excessive winter defoliation or dark brown root systems.
  2. Plantations should be established only in well drained areas. If excess water from any source collects in the planting site, avoid planting Fraser fir or other root rot susceptible species. In addition, nursery beds and line-out beds should be located where there is no danger of flooding and the soil should have good internal drainage. To encourage good drainage, seedling and lineout beds should be built up at least 6 to 8 inches.
  3. Never set Fraser fir transplants deeper than 1 inch above the root collar and make sure roots are spread properly at planting.
  4. In areas where plants have died from Phytophthora root rot, only replant with species that are not susceptible to this disease.
  5. In the nursery bed, trained pesticide applicators can use methyl bromide at a rate of 2 lbs/100 sq. ft. released under an airtight cover such as plastic to reduce the fungal spore population as well as weeds. Methyl bromide should only be applied when soil temperatures are above 50 F. Leave the plastic cover in place after application for at least 48 hours
  6. The fungicides SUBDUE GR, SUBDUE 2X WSP and SUBDUE MAXX are labeled for use on conifers in plantations and seedbeds.  These products should be applied in the early spring and again in the late summer. SUBDUE should never be applied to fir growing on bottom lands or poorly drained soils or near surface water as it will not be effective in eradicating the fungus and may contaminate streams. If a small disease outbreak is occurring in a field, it is NOT necessary to apply these chemicals to the entire field, but rather the area, in and around the infected trees should be treated. It must be emphasized that trees growing close to symptomatic trees may be infected, but are not yet showing symptoms. These infected, symptomatic trees should be targets of your SUBDUE applications.

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The use of brand names and any mention or listing of commercial products or services does not imply endorsement by the North Carolina Agricultural Extension Service nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label.

Published by North Carolina Cooperative Extension Service Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

Webpage updated Feb. 2001