Agriculture Reference
In-Depth Information
animals. The fungus has a wide host range among weeds
and crop plants.
Warm, dry conditions favour infection and disease
development.
Importance
Charcoal rot can cause plant death in groves grown in
infested soil, particularly during periods of hot, dry
weather when irrigation is insufficient to maintain
adequate moisture levels.
Management
•
Maintain adequate soil moisture levels to prevent plant
stress.
LEAF MOULD (OLIVE LEAF SPOT)
■
Cause
The fungus
Pseudocercospora cladosporioides
(syn.
Cercospora cladosporioides
,
Mycocentrospora
cladosporioides
).
Fig 13.5 Anthracnose symptoms on olive fruit.
Symptoms
Grey, mouldy blotches develop on the undersides of leaves
while the upper surface turns yellow then brown. Infected
leaves may fall from the plant, causing some defoliation.
Fruit may also be infected, developing small, brown sunken
spots with a greenish margin.
Source of infection and spread
Spores of the fungus are dispersed by wind during wet,
humid weather and temperatures in the range of 12-28
Fig 13.6 Anthracnose on olive fruit.
°
C
CHARCOAL ROT
favour disease development. The fungus survives in old,
infected leaves, which remain attached to the tree. Infection
often occurs during autumn so inoculum is then available
to infect young leaves produced in the following spring.
■
Cause
The fungus
Macrophomina phaseolina
.
Symptoms
Dieback of shoots occurs and leaves drop from affected
plants. These symptoms are most likely to develop when
plants are stressed during hot, dry weather. Roots on affected
plants appear grey and are dotted with pinhead size, black
fungal sclerotia. Severely affected roots blacken and rot.
Source of infection and spread
The fungus is soil-borne and survives as sclerotia in soil for
many years. It can be spread by any means that moves
infested soil, including water, farm implements, wind and
Fig 13.7 Leaf mould. Mouldy blotches develop on the underside
of leaves (top).
