3[7] Phellinus[EDFS

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This leaflet is produced by the Ministry of Agriculture & Livestock, Solomon Islands, with support from IPPSI:
Improved Plant Protection in Solomon Islands, a project financed by ACIAR, the Australian Centre for
International Agricultural Research, Canberra. Authors: Helen Tsatsia, MAL & Grahame Jackson, TerraCircle
Inc.

Extension Fact Sheet 3:

Cocoa Brown Root Rot

Common name: Brown root rot

Scientific name: Phellinus noxius

Hosts: The fungus has a wide host range, attacking native forest trees and plantation crops,
including cocoa, oil palm, rubber, coffee and Cordia (especially in Vanuatu).

Damage

The fungus attacks the roots, and
this causes the leaves to yellow
and wilt, beginning at the branch
tips. Very quickly, all the leaves
fall. The fungus forms a dark
brown to black crust on the trunk
with a white margin, often with
clear drops of liquid; the crust
grows up to one metre (photo,
left). It grows on the roots, too,
and often soil and small stones
can be seen within it.

Once a tree is infected, there is no
way to cure it: it will die. If left
unattended, the fungus will spread
outwards along the roots to
healthy trees around; infection
of these will lead to their death
and further spread, so that in a
short time a large number of trees are killed.

Biology and Life Cycle

Phellinus lives in the forest where, under natural conditions, it does little harm. However,
when the trees are cleared for cocoa or a plantation of timber trees, condition becomes ideal
for its spread. In the new plantation, all the trees are alike and if susceptible to Phellinus,
spread is rapid.

The fungus spreads from the old stumps, left when the forest was cleared. These become
infected by spores or more likely by the fungus in the soil. The fungus spreads from these to
the cocoa by root-to-root contact. Eventually, it reaches the base of the tree and climbs the
outside. The fungus has enzymes to extract nutrients from dead and dying roots and stems.
The life cycle is illustrated above (diagram

The crust is sterile, that means it does not produce spores. However, spores are produced in
the brackets. These are dark brown above with red-brown margins and grey underneath. They
have not been seen on cocoa in Solomon Islands, but thp;not been seen on cocoa in Solomon Islands, but they occur on rotten stumps of many
forest trees (photo, centre) and on Leucaena (photo, right).

Signs and Symptoms

Routine inspection of the base of the trees is necessary to look for the crust that grows up the
trunk. Also, look for brackets of the fungus on old stumps of forest trees. Also, look for them
on shade trees, e.e., Leucaena.

Management

Cultural control:

After clearing the forest, it is important to survey stumps that have brackets of Phellinus
growing from them. These should be removed together, if possible, with all roots larger than
2.5 cm diameter. The surveys need to be done on a regular basis, every 3 months at least.

If diseased cocoa trees are seen, remove them immediately, taking out as much of the larger
roots as possible. Also, carefully remove the soil from around the trees nearby and inspect for
the crust at the base of the trunk and on the larger roots. If seen, remove the trees.

Chemical control:

There is no chemical control option for this disease.

The diagram of the life cycle is from APSnet Education Center. Brown root rot. The permission of The American Phytopathological

Society to use this diagram is gratefully acknowledged. http://www.apsnet.org/education/LessonsPlantPath/BrownRootRot/default.htm