Symptoms and Signs
The most distinctive symptoms of Phytophthora root rot are the brown lesions on roots of all sizes. The xylem of the roots above the lesions often turns yellowish or brown. In severe cases, nearly all roots may be girdled or rotted off. Aboveground, infected plants are slow growing and may wilt or die in hot weather. When fruit in contact with the ground are infected, the disease is called buckeye rot. Symptoms include tan or brown spots with concentric rings. Phytophthora capsici also causes greasy, purple-brown stem lesions.
Comments on the Disease
Phytophthora parasitica and P. capsici occur in most soils. Infection of plants occurs at any stage of growth when there is free water in the soil. Damage is greatest in poorly drained, compacted, or overirrigated soils.
Management
Good water management is key to managing this disease and avoiding the need for fungicide treatments.
Cultural Control
Provide good drainage and prevent flooding. Avoid wide fluctuations in soil moisture, which predisposes plants to infection. Keep tops of bed dry to avoid buckeye rot of the fruit. Planting cereals as a rotation crop may reduce the level of infestation in the soil. Resistant varieties are not yet commercially available.
Organically Acceptable Methods
Cultural control is acceptable in an organically certified crop.
Chemical Control
Fungicides are needed only in poorly drained soils or where root rot is historically a problem.
| Common name | Amount per acre** | REI‡ | PHI‡ |
| (Example trade name) | | (hours) | (days) |
| |
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used. |
|
| A. | MEFENOXAM |
| (Ridomil Gold SL) | 1 pt | 48 | 7 |
| MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4) |
| COMMENTS: Follow application with an irrigation (see label). |
| ** | See label for dilution rate. |
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment until harvest can take place. In some cases the REI exceeds the PHI. The longer of these two intervals is the minimum time that must elapse before harvest may take place. |
| 1 | Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number. |
Text Updated: 12/13
Treatment Table Updated: 12/13
FAQs
Hydrogen Peroxide — The application of a 3% solution of household hydrogen peroxide to your soil is effective in killing pathogens and diseases like Phytophthora. Apply a mixture of 1 part peroxide to 3 parts water and allow it to penetrate the soil before regular watering resumes.
What is the best fungicide for Phytophthora root rot? ›
Aliette (fosetyl-Al) is also effective against Phytophthora and is registered for use on a few woody ornamentals. Captan has been shown to be effective and Truban (and other ethazol-containing fungicides), and maneb have been reported to be helpful in some cases.
How to treat root rot in tomatoes? ›
Prune affected roots and consider fungicides for treatment. Balance soil moisture with the "soak and dry" method to prevent rot.
What is the solution for Phytophthora? ›
We recommend the use of PHOSPHO-jet, a systemic fungicide for treatment of Phytophthora, using two steps. First, a micro-injection of PHOSPHO-jet into susceptible host trees, followed by ammending the soil around the tree with humates, as Phytophthora thrives in poorly drained and anaerobic soils.
What is the systemic fungicide for Phytophthora? ›
Phosphite, also known as phosphorous acid, or phosphonate, is a systemically-applied liquid fungicide developed for the control of Phytophthora diseases. Not to be confused, phosphite is a variation of phosphate - the plant-available form of phosphorous essential for plant growth.
What is the best treatment for root rot? ›
Using clean secateurs cut back and get rid of any rotten/dead/damaged roots. Thoroughly disinfect the pot before repotting your plant in fresh compost. Now that the root ball may be much smaller, using clean secateurs, prune back your plant's leaves by one third to a half - so it doesn't have to photosynthesise as much ...
What chemicals are used to treat Phytophthora? ›
Chemical/Microbial Control of Phytophtora Blight
| Product | resistance group | Mix required |
|---|
| Presidio | 43 | Soil – no Foliar -yes |
| Ranman | 21 | Soil – no Foliar–surf |
| Revus | 40 | Foliar – copper/surf |
| Zampro | 40 & 45 | Soil – yes Foliar-surf |
Orondis® brand fungicides and their best-in-class active ingredient promote plant health from the ground up while combatting key oomycete diseases like Phytophthora root rot and crown rot in citrus, tree nuts and other labeled perennial crops.
What is a systemic fungicide for root rot? ›
Plant Doctor is both a preventative and curative. It will control pythium & phytophthora (root rot) as well as powdery mildew (foliar disease).
Will hydrogen peroxide help tomato root rot? ›
Turns out it can work wonders on a sick plant. The way it works is the chemical in hydrogen peroxide kills the bacteria that causes root rot in plants and breaks down into the soil to release extra oxygen to encourage the growth of healthy, new roots.
Once root rot is identified, you must determine if the plant can be saved. If the entire root system has already become mushy, it is too late to save the plant. However, if some healthy, white, firm roots exist, try to bring the plant back to good health by replanting in fresh soil with good drainage.
How do you fix root rot fast? ›
How to Treat Root Rot
- Remove the pot and soil.
- Trim away damaged roots and leaves.
- Repot the plant.
- Research plant care requirements.
- Check the soil before watering.
- Select a well-draining potting mix.
- Use growing containers with drainage holes.
- Make sure the plants receive enough light.
Where the disease is new or localised in the garden, affected plants should be destroyed and the soil from the root-run replaced with fresh topsoil. Replanting should be done with less susceptible species. In practice, the host range will vary between different Phytophthora species.
How to stop the spread of Phytophthora? ›
Phytophthora spp. release swimming spores in water and waterlogged soil. To prevent disease, do whatever you can to prevent standing water. Prepare the nursery site to have an adequate slope and install tile drains and irrigation channels to convey water to a central location for treatment.
What are the control measures of Phytophthora? ›
Therefore, if Phytophthora is present, metalaxyl should be used to minimise disease development. Roadways, interrows and equipment should be kept clean. The site should be well-drained to avoid water from forming ponds that may subsequently allow Phytophthora to proliferate.
How do you manage Phytophthora diseases? ›
Disease is very hard to manage once present in a field, so focus on prevention. Phytophthora travels through water. Plant in well-drained fields and use raised beds to improve drainage and avoid working in impacted fields that are wet. Rotate out of cucurbit and solanaceous crops for a minimum of three years.
How do you solve root rot? ›
Wash the plant roots under running water to clean the soil off. Use sterilized scissors to trim away rotting roots. Prune back the foliage of your plant. It's heartbreaking but less foliage means the new smaller root system doesn't have to work as hard and will have time to grow.
How do you treat Phytophthora root rot in boxwoods? ›
Apply fungicide soil drench if Phytophthora root rot is present. Monitor for psyllids, mites and leafminers. Treat as needed. Excavate mulch from root collars and add finely ground pine bark mulch to root zone as needed.
What should be done with plants confirmed to be infected with Phytophthora? ›
Do not move plants that appear sick or dying. Disinfest pruning and other gardening tools between plants. Because P. ramorum is a water mold that thrives in wet conditions, reduce standing water in your yard or garden and avoid overhead irrigation.
