Tree problems · Disease
Phytophthora root rot: signs and what to do
Phytophthora root rot is a tree disease, often seen on flowering dogwood, eastern white pine, Douglas fir. Look for: yellowing, wilting or dwarfed leaves or needles, even when soil is wet.
General information, not a diagnosis. A certified arborist or your county extension office can confirm.
- Disease
- Flowering dogwood
- Eastern white pine
- Douglas fir
- Leyland cypress
- Arborvitae
- Japanese maple
Signs to look for
Tick what you see. More ticks make it more likely, but only an on-site look can confirm.
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Season
The pathogen is most active when soil is warm and wet. Crown symptoms often show in summer, when roots can not keep up with the water the tree needs.
How it spreads
Water molds called Phytophthora live in the soil and move in wet soil, runoff and irrigation water. They also travel on infected nursery stock, soil and tools.
Where it is found
Phytophthora root rots occur in many parts of the United States, especially in heavy, poorly drained soils, and different species attack different trees. Check your state official map; ranges change.
Official sources
What to do
- 1
Check the drainage first. Look for standing water, a high water table, low spots or soil that stays soggy.
- 2
Dig carefully around the root flare to look at roots. Healthy roots are firm and light; rotted ones are soft and dark.
- 3
Improve drainage where possible and stop watering a tree that is already in wet soil.
- 4
Plant the root flare at or just above soil level, and keep mulch thin and off the trunk.
- 5
Replace with a species suited to wet or heavy soil. Ask your local extension office for a list.
Safety first: do not climb, do not cut near power lines and do not use a chainsaw on storm-loaded wood. Call the utility for downed lines and 911 if anyone is in danger.
Prevention
Match the tree to the site. Avoid planting sensitive species in heavy clay or low, wet spots. Plant high, water by need not by schedule, and buy healthy stock from a trusted nursery.
When to call a pro
Call an arborist if a newly planted or established tree is yellowing with dieback in wet soil, or if you see dark cankers at the base. A pro can check roots, help with drainage and tell you if a lab test makes sense.
Not sure who to call? Read how to hire a tree service or check is my tree dangerous?
Trees it affects
Usually seen on: Flowering dogwood, Eastern white pine, Douglas fir, Leyland cypress, Arborvitae, Japanese maple, Southern magnolia.
- Flowering Dogwood
- Eastern White Pine
- Douglas-fir
- Leyland Cypress
- Arborvitae
- Japanese Maple
- Southern Magnolia
See all species in our tree library, or pick a tougher tree with the tree picker.
For tree companies
How to explain Phytophthora root rot to a customer
Tell customers that many root problems come from too much water, not too little. Look at drainage and planting depth before talking about chemicals. Be honest that fungicides do not fix badly drained sites.
Send this page to the customer after your visit so they can read the signs in plain words. See also selling plant health care and the job photo checklist.
Questions
Is Phytophthora a fungus?
It acts like one, but it is a water mold. That is why it likes wet soil and is not stopped by the same products as true fungi.
Why does my tree look thirsty when the soil is wet?
Rotted roots can not take up water well, so leaves wilt or yellow even in wet soil. This is a classic sign of root rot.
Can I save a tree with root rot?
If damage is early, better drainage and less watering can help. Trees with extensive root decay often keep declining.
Will it spread through my yard?
It can move through wet soil and runoff to nearby susceptible plants. Fixing drainage helps limit it.
Do chemical treatments work?
Some products are labeled for use on certain plants and can help protect them, but they do not fix poor drainage. Follow the label and ask an extension office or licensed pro.
What can I plant in a wet spot?
Species that tolerate wet soil do better there. Your local extension office can give a list for your area.
Can Lirevon diagnose Phytophthora root rot on my tree?
No. Lirevon is a remote marketing team for tree service companies and does not do tree work. This page is general information, not a diagnosis. A certified arborist or your county extension office can confirm what is wrong with your tree.
How do I find a good local pro for this?
Search Google Maps for certified arborists or tree services near you, read their reviews and ask for proof of insurance. Get two or three written quotes. Our guide on how to hire a tree service lists the questions to ask.
Related tree problems
- Drought Stress (Other damage)
- Armillaria root rot (shoestring root rot) (Disease)
- Bagworms (Insect)
- Cankers (Disease)
- Construction Damage (Other damage)
- Girdling Roots (Other damage)