UC IPM: UC Management Guidelines for Armillaria Root Rot on Kiwifruit

UC Pest Management Guidelines

Kiwifruit

Armillaria Root Rot

Pathogen: Armillaria mellea

(Reviewed 3/07, updated 3/07)

In this Guideline:

Symptoms
Comments on the disease
Management

SYMPTOMS

Vines infected with Armillaria root rot usually completely collapse. Occasionally, white mycelial mats can be found under the bark at the soil line, but more commonly white mycelial strands are seen interwoven through darkened cortical tissue. Dark, rootlike structures called rhizomorphs grow from the root into the soil after symptoms develop on vines.

COMMENTS ON THE DISEASE

The fungus survives on diseased wood and roots belowground for many years. Healthy plant roots can become infected when they come in contact with inoculum from a preceding orchard crop or nearby oak trees. Although kiwifruit plants are somewhat tolerant of this fungus, if the vine has already been weakened by Phytophthora infection, its death may be hastened by an invasion of A. mellea. Flood waters sometimes spread infected roots in a vineyard. The fungus is favored by soil that is continually damp. Although the pathogen produces mushrooms, they are not considered significant in disease spread.

MANAGEMENT

When clearing land for planting or replanting vines, carefully remove and burn roots 1 inch or greater in diameter. Preplant fumigation can reduce soil inoculum.

Common name

Amount/Acre

R.E.I.+

(trade name)

(hours)

When choosing a pesticide, consider information relating to environmental impact.

METHYL BROMIDE*

Label rates

see label

COMMENTS: Preplant treatment. Must be applied under a Critical Use Exemption only. Fumigants such as methyl bromide are a prime source of volatile organic compounds (VOCs), which are a major air quality issue. Fumigate only as a last resort when other management strategies have not been successful or are not available.

*	Permit required from county agricultural commissioner for purchase or use.
+	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment until the orchard can be harvested. In some cases the R.E.I. exceeds the P.H.I. The longer of these two intervals is the minimum time that must elapse before harvest may take place.

UC IPM Pest Management Guidelines: Kiwifruit
UC ANR Publication 3449
Diseases
J. E. Adaskaveg, Plant Pathology, UC Riverside
T. J. Michailides, Plant Pathology, Kearney Agricutural Center, Parlier
W. D. Gubler, Plant Pathology, UC Davis
Acknowledgment for contributions to the disease section:
C. Arredondo, Plant Pathology student, UC Davis
K. Conn, Plant Pathology, UC Davis

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