Phytophthora abietivora fact sheet

Background

Phytophthora abietivora is a recently documented pathogen that was originally isolated from diseased Christmas trees (fraser fir, Abies fraseri) in Connecticut in the United States^Footnote 1. It was later reported from Pennsylvania and Virginia in the natural environment^Footnote 2. In Canada, it has been reported from Quebec and Ontario. In Quebec, it was reported from forest nurseries and Christmas tree plantations, where it was associated with root rot^Footnote 3. In Ontario, it was reported in environmental samples from forested areas, but has not been associated with any disease.

Hosts

P. abietivora has been associated with root rot disease in several hosts, including balsam fir (Abies balsamea), fraser fir (Abies fraseri), hickory (Carya sp.), flowering dogwood (Cornus florida), American witch hazel (Hamamelis virginiana), mountain holly (Ilex montana), white oak (Quercus alba), and eastern hemlock (Tsuga canadensis). Other host associations include red maple (Acer rubrum), silver birch (Betula lenta), American beech (Fagus grandifolia), chestnut oak (Quercus montana) and northern red oak (Quercus rubra).

Symptoms

P. abietivora is associated with root rot, which causes foliar chlorosis, discolouration, stem cankers, and may lead to tree decline and death (Figure 1, 2, 3, 4 and 5)^Footnote 2. Young saplings are most at risk, but the disease can affect older trees as well. It may be confused with other abiotic conditions or other root rot diseases. Laboratory testing is needed to confirm identification.

Best management practices

Wet, cool conditions provide ideal environments for this pathogen. Phytophthora species, including P. abietivora, can be spread through soil and water, as well as via infected plant material such as seedlings or contaminated equipment such as pots or trays (particularly if soil remains on the equipment). Restricting movement of potentially infested material and planting healthy seedlings can help to restrict the movement of this pest.

Photos of the symptoms of phytophthora abietivora