Agriculture Reference
In-Depth Information
Fig 14.19 Two different symptoms of brown spot on papaya fruit.
Fig 14.17 Black spot on green papaya fruit.
Symptoms
Small, light brown, circular spots develop on the lower
leaves, gradually moving to the younger leaves. Mature
spots have brown centres, 2 mm in diameter, surrounded
by a prominent yellow halo. The spots may coalesce under
favourable conditions, causing extensive areas of leaf death.
Long, elliptical spots, with a dark coating of spores, develop
on leafstalks. Small, dark, sunken spots occur occasionally
on the surface of fruit.
Source of infection and spread
Spores develop on diseased leafstalks and leaves and are
spread by wind and water splash with hot, humid
conditions favouring disease development.
The fungus has a wide host range, including cucurbits,
tomato and legumes.
Fig 14.18 Black spot on ripe papaya fruit. Inset: enlarged symptoms.
Importance
The disease occurs in most countries where papaya is
grown. It is a common and often serious disease in south
Queensland, causing extensive defoliation of plants in the
absence of adequate control measures.
Importance
Brown spot is a serious disease in hot, wet areas, causing
extensive loss of leaves and reduced yields and fruit quality.
Management
•
Apply recommended fungicides as required. Good
coverage of plants, particularly the undersides of leaves,
is essential for adequate control.
Maintain a high standard of plantation hygiene and
regularly remove diseased leaves and fruit, which are
the major source of inoculum.
•
BROWN SPOT (CORYNESPORA
LEAF SPOT)
■
Cause
The fungus
Corynespora cassiicola
.
Fig 14.20 Brown spot symptoms on the underside of papaya leaves.
