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How to Manage Pests
UC Pest Management Guidelines
Grape
Armillaria Root Rot (Oak Root Fungus)
Pathogen: Armillaria mellea
(Reviewed 6/06,
updated 10/08)
In this Guideline:
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Vines infected with Armillaria root rot become nonproductive and
often die within 2 to 4 years. Adjacent vines may develop weak, shorter shoots
as they are infected by the pathogen. White mycelial
mats can be found under the bark at the soil line. Dark, rootlike
structures (rhizomorphs) may be seen growing in the soil near infested
grapevine roots.
The fungus survives on diseased wood and roots below ground for many
years. Healthy plant roots can become infected when they come in contact with
inoculum, including rhizomorphs, from a preceding orchard crop or nearby oak
trees. 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.
Because there are no known Armillaria-tolerant grape rootstocks,
preplant chemical fumigation of the soil is the only control for oak root
fungus. Treatment is best undertaken in September to November when the soil is
still dry. Several preparatory steps are involved:
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Before planting or replanting in affected soil, remove,
pile, and burn all diseased vines, tree stumps, and roots greater than 1.5 inch
in diameter.
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In treating portions of an existing vineyard, healthy
appearing vines adjacent to those showing symptoms are often also infected and
should be removed. If removed, include the area in the fumigation treatment.
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Before fumigation with methyl bromide or sodium
tetrathiocarbonate, dry out the soil as much as possible. The drier the soil,
the deeper the chemical will penetrate and the more effective the treatment
will be. Do this by withholding water during summer and by using cover crops
(such as sudangrass or safflower) to further deplete soil moisture. Finally,
deep-till the dried area, being careful not to spread any diseased roots.
| Common name |
Amount/Acre** |
R.E.I.+ |
P.H.I.+ |
| (trade name) |
|
(hours) |
(days) |
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| When choosing a pesticide, consider efficacy and the general properties of the fungicide as well as information
relating to environmental impact. |
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| A. |
METHYL BROMIDE* |
Label rates |
48 |
NA |
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COMMENTS: Preplant
treatment. May only be used under a Critical Use Exemption. Fumigants such as
methyl bromide are a source of volatile organic compounds (VOCs) but are not reactive
with other air contaminants that form ozone: methyl bromide depletes ozone.
Fumigate only as a last resort when other management strategies have not been successful or are not available. |
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| B. |
SODIUM TETRATHIOCARBONATE |
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(Enzone) |
Label rates |
4 days |
NA |
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COMMENTS: Make application 1–4 weeks before planting. |
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| C. |
METAM SODIUM* |
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(Vapam, etc.) |
Label rates |
48 |
NA |
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COMMENTS: Apply in
winter when soil moisture is high. Fumigants such as metam sodium are a
source of volatile organic compounds (VOCs) but are minimally reactive with
other air contaminants that form ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available. |
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UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448
Diseases
W. D. Gubler, Plant Pathology, UC Davis
R. J. Smith, UC Cooperative Extension, Sonoma County
L. G. Varela, UC IPM Program, Sonoma County
S. Vasquez, UC Cooperative Extension, Fresno County
J. J. Stapleton, UC IPM Program, Kearney Agricultural Research Center, Parlier
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley
Acknowledgment for contributions to Diseases:
G. M. Leavitt, UC Cooperative Extension, Madera County
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