Phytophthora Fruit Rot Pest Control

Phytophthora Fruit Rot Pest Control Information

By Josie Borlongan, Garden Guides Contributor

About Phytophthora Fruit Rot

Phytophthora root rot is caused by several related species of soil-borne fungi belonging to the genus Phytophthora. It is known as a "plant destroyer" or "plant pathogen." It can reproduce sexually or asexually.

Almost all fruit, nut and ornamental trees and shrubs can develop Phytophthora root and crown rot if soil around the base of the plant remains wet for a long time.

Prevention and Control

Avoid prolonged saturation of the soil or standing water around the base of susceptible trees. Avoid heavy watering; water only when necessary and irrigate only as needed. Keep track of the soil moisture and ensure that there is proper drainage. A good drainage should be 3 to 6 ft in depth for trees, 2 to 4 ft for shrubs and 1 to 2 ft for bedding plants.

Remove infected plants together with the soil in the immediate vicinity of the roots and crown.

Fungicides can be used for prevention but not for treatment of infected plant; 8G or (Truban 5G) and mefenoxam (Subdue GR) can be applied in the home landscape.

Affected Plants

Trees, shrubs and woody perennials; maples (Acer), Lawson cypresses, yews (Taxus), apples, rhododendrons, raspberries, and heathers are most commonly attacked. Other plants that are known to be susceptible are:
Raspberries (red, black and purple)


Infected plants become weak and stunted and are particularly susceptible to winter injury; seriously infected plants commonly collapse and die.

Patches of dead tissue may appear on the stem or the trunk with bluish-black stains in the tissue beneath. The leaves of plants affected by Phytophthora root rot appear drought stressed, ranging in colors from dull green or yellow to red or purplish. Trees or plants often wilt or die rapidly with the first warm weather of the season.

Predator Insects

Fungus-eating ladybird

Natural Insecticides

Organic fungicides can be used but may not be very effective.

Other Methods of Control

* Improve Drainage: Build a mound to improve drainage.
* Selection of Planting Stock: Buy only good-quality plants from reputable sources; choose those tolerant to Phytophthora. Less-susceptible rootstocks for varieties are available for almonds and stonefruit, apples, cauliflowers and strawberries.
* Rotation: If tomatoes have been affected by Phytophthora root rot, avoid planting tomatoes or other susceptible plants such as eggplant in the same soil for at least one to two seasons. Plant a resistant crop, such as corn, instead.

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