How to Manage Pests
UC Pest Management Guidelines
Phytophthora Root Rot
Pathogen: Phytophthora parasitica and P. capsici
In this Guideline:
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 color. 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.
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.
Good water management is key to managing this disease and
avoiding the need for fungicide treatments.
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
Organically Acceptable Methods
Cultural control is acceptable in an organically certified crop.
Fungicides are needed only in poorly drained soils or where root rot is
historically a problem.
| (trade name)
|When choosing a pesticide, consider information relating
to environmental impact Not all registered pesticides are listed. Always read label of product being used.
||(Ridomil Gold) EC
||MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4)
||COMMENTS: Follow application with an irrigation (see label). Do not apply more than 3 pt/treated acre/season.
UC IPM Pest Management Guidelines: Tomato
UC ANR Publication 3470
R. M. Davis, Plant Pathology, UC Davis
G. Miyao, UC Cooperative Extension, Solano/Yolo counties
K. Subbarao, USDA Agricultural Research Station, Salinas
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier
Acknowledgments for contributions to the disease section:
B. W. Falk, Plant Pathology, UC Davis
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