what can you tell me about phytophthora - Knowledgebase Question

northlake, Il
Question by duncanmary
October 23, 2009
we got the lab report on my neighbors siberian elm which the roots reach into my yard and we dug because of sinking and we found rotting roots had the lab test elisa analysis and it came back with this fungus & I am worried about my plants,maple tree and perennials thanks for any info

Answer from NGA
October 23, 2009


The fungus Phytophthora is capable of causing root, crown, and collar rot diseases of woody plants, especially those in moist sites. Susceptible plants include apple, arborvitae, azalea, beech, birch, boxwood, Chamaecyparis, cherry, dogwood, elm, fir, forsythia, Franklin-tree, hemlock, horsechestnut, Japanese holly, juniper, maple, oak pear, Pieris, pine, plum, Rhododendron, sweetgum, tuliptree, and yew.

Poorly drained soil or wet sites favor the disease. Phytophthora produces zoospores which are motile in water allowing the fungus to swim from infected to healthy roots in flooded or waterlogged soils. In addition to aiding dispersal, wet soils stress the root systems, making them more susceptible to Phytophthora diseases.

Infection can occur when soil temperatures are in the 60's and 70's F. Soil moisture just below saturation allows sporangia to form in a few hours and motile zoospores to be released soon after. Zoospores infect feeder roots just behind the root cap. The fungus can be splash-dispersed during heavy rains or overhead irrigation. In the nursery, the fungus can be carried in run-off from plant to plant in the field or from an infected plant to the drain holes of containers of nearby healthy plants. Phytophthora overwinters in the soil and in plant debris in the form of resistant oospores enabling the fungus to survive in soil and plant debris for long periods of time.

Since the fungus travels in water your best defense is to make sure the soil drains well. You might consider installing drain tiles or a curtain drain between the roots of your maple and your neighbor's property. Maple roots typically extend out at least as far as the longest branches of the canopy, and usually half again. For other ideas, contact your local cooperative extension office. Although your zip code puts you in Cook County, there are multiple offices so rather than guess, I'm sending you a list of offices so you can choose the one that's most convenient: http://web.extension.uiuc.edu/...

Hope this answers all your questions.

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