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How to Manage Pests
UC Pest Management Guidelines
Almond
Armillaria
Root Rot (Oak Root Fungus)
Pathogen: Armillaria
mellea
(Reviewed 1/05,
updated 1/05)
In this Guideline:
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Roots infected with Armillaria mellea have white to yellowish fan-shaped
mycelial mats between the bark and the wood. Dark brown to black
rhizomorphs sometimes can be seen on
the root surface. All stone fruit rootstocks are susceptible to Armillaria root
rot. The plum rootstock Marianna 2624 has some tolerance and may be useful in
some situations.
The fungus survives on dead roots.
The only treatment is fumigation. Before chemical treatment, remove all
infected trees, stumps, and as many roots greater than 1 inch in diameter as
possible. Healthy-appearing trees adjacent to those showing symptoms are often
infected also. Removal of these adjacent trees and inclusion of that ground in
the soil fumigation may be advisable. Infected trees, stumps, and roots should
be burned at the site or disposed of in areas where flood waters cannot wash
them to agricultural lands. Complete eradication is rarely achieved, and
retreatment may be necessary in localized areas. If the soil is wet or if it
has extensive clay layers to the depths reached by the roots, fumigant
treatment may not be successful. The greatest opportunity for eradication
occurs on shallow soils less than 5 feet in depth. Treat Armillaria from
late summer to early fall.
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Amount/Acre |
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PREPLANT |
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| A. |
METHYL BROMIDE* |
Label rates |
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COMMENTS:
Any use of methyl bromide after Dec. 31, 2004 must be allowed under a critical
use exemption. Dry soil by withholding water during summer and using cover crops such as
sudangrass or safflower. The drier the soil the better for deep penetration. After drying,
deep-till just the area that will be fumigated. If the soil is dusty, wait for an early rain
before ripping and fumigation. Ripping a dry soil that is silty can result in large clods on the
surface. Inject methyl bromide 18 to 30 inches deep with chisels and cover with gas-proof
cover. Increasing the dose tends to increase the depth of penetration, but it cannot be relied
upon to penetrate wet soils, especially if soils are high in clay. Do not remove the cover for at
least 2 weeks and aerate 1 month before planting.
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| B. |
SODIUM TETRATHIOCARBONATE |
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(Enzone) |
Label rates |
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COMMENTS: Make two applications to moist soil. Be
sure to remove large roots as well as smaller roots
(pencil size) from soil planting site (10 x 10 ft area) before treatment. |
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![[Precautions]](/IMAGES/btn-precautions_bul.gif)
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UC IPM Pest Management Guidelines: Almond
UC ANR Publication 3431
Diseases
W. D. Gubler, Plant Pathology, UC Davis
J. E. Adaskaveg, Plant Pathology, UC Riverside
Roger Duncan, UC Cooperative Extension, Stanislaus County
J. J.
Stapleton, UC IPM Program, Kearney Agricultural Center
Acknowledgment for contributions to the disease section:
B. L. Teviotdale, Kearney Agricultural Center, Parlier
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