Phytophthora Root and Stem Rot

There are various specious of phytophthora fungi that cause root and stem rot in plants. Plants in wet soils and warm humid conditions are more likely to be infected. Some strains of phytophthora fungus are host-specific; others attack a range of plants.

Susceptible Plants- Azelea, rhododendron, Lawson Cyprus, beech, heather, apple, raspberry, yew, linden, ornamental Prunus, and many other woody plants can all be affected by this fungus.



Symptoms- Phytophthora can cause the plants to have sparse, yellowing foliage. There can be partial dieback of twigs, whole branches ,or one side of a shrub or tree. On fruit bearing trees the fruit becomes smaller and sparser. Trees infected with phytophthora increase little in height or diameter and generally will die within three to ten years after the initial infection.

Tongues of dead bark can extend up the stem from soil level. On examination, roots at that point will be dead. On smaller specimens lower leaves may drop and the entire plant wilts. Phytophthora is difficult to diagnose and can be confused with other, less severe problems.

Prevention and Control- Planting sites should be well-drained. Growers and gardeners often misinterpret wilt as a sign that a plant needs water and respond by applying more water when if fact the wilt may be caused by waterlogging.. This reaction should be avoided in sites where plants are clearly receiving adequate water. The use of drain tiles to prevent rain water from collecting on the surface is suggested. Special care should be taken to set plants high so that the soil line is not more than one inch above the upper roots.

Where subsoils are known to be poorly drained, planting on raised beds should be considered. After planting, the soil should not be mounded up around the base of the stem because this increases susceptibility to phytophthora fungal disease. Avoid transferring contaminated soil on boots and equipment. There is no cure for phystophthora.

Fungicidal/Bactericide Control- Oxidate




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