Agriculture Reference
In-Depth Information
lesions, limited by the veins (which may also be invaded)
and become dark brown. Lesions range in size up to
about 8 mm and may coalesce to form larger
necrotic areas.
The margins of the leaf spots are often darker than the pale
brown centres. Leaf spots are very obvious on senescing
leaves owing to the green-island effect with lesions on a
yellow-orange background. Severe symptoms occur
commonly in late summer and early autumn, which result
in complete leaf loss by winter. Twig and fruit infection
have not been observed.
Source of infection and spread
The fungus survives in affected leaves that fall from trees
in autumn and on volunteer suckers and seedlings that
grow during the winter months. Fungal spores are
dispersed by wind and rain, and infect new growth in
spring following rain or heavy dews.
Fig 19.15 Fruit rot symptoms on rambutan.
Source of infection and spread
Latent infections may form in the skin or stem end of
fruit before harvest. Lesions usually develop during fruit
ripening. Water stress may favour fruit infection.
Importance
Leaf spot is a common and widespread disease of
economic importance in persimmon. All astringent
and non-astringent varieties are affected but
differences in their relative susceptibility exist. The
disease causes substantial premature leaf drop during
autumn, which reduces starch accumulation by trees,
resulting in lower yields and smaller fruit size in
subsequent crops.
Importance
Stem-end rot causes occasional losses of harvested rambutans.
Management
•
Apply registered protectant fungicides as required.
RAMBUTAN
(
Nephelium lappaceum
)
STEM-END ROT
■
Cause
The fungi
Botryosphaeria
spp. and
Phomopsis
spp.
Symptoms
The disease first appears as a brown discolouration of the
skin at the stem end of the fruit. In advanced stages of
infection, white hyphal growth may appear on the surface
of lesions.
Lasiodiplodia theobromae
can also cause
stem-end rot symptoms.
Fig 19.16 Stem-end symptoms of fruit rot on rambutan.
