3. HISTORY:
Carica papaya - Native distribution of papaya ranges
from Mexico
Odium caricae introduced by Noack(1898)
Powdery mildew occurs throughout the world where
conditions are relatively warm and moist
6. SYMPTOMS:
On the upper surface of disease of leaves are found patches of
whitish powdery growth occurs
The disease appear on the foliage and pods
Occasionally fungus may attack the stem of young seedling
when grown under reduced light condition.
The spots enlarge and cover the entire leaf area. Severely
infected leaves may become chlorotic and disorted before
falling.
7. Fungus:
It is obligate parasite
The mycelium is hyaline septate and haustoria
develop in epidermal cells
Conidia are hyaline, granular in type
9. Mode of spread:
The fungus spreads through wind borne conidia
The powdery mildew fungus overwinters in dormant
buds
Secondary spread of the disease can occur if spores
are produced in these new infections
10. Disease cycle:
The fungus overwinters in infected leaves on the
ground and possibly in diseased shoots
The overwinters spore (oospore) germinates in the
springs and produces a different type of spore
(sporangium)
The sporangia are spread by wind and splashing rain
11. When plant parts are covered with a flim of moisture
the sporangia release smell swimming spores called
zoospore
Zoospore germinate by producing a germ tube that
enters the leaf through stomates on the lower leaf
surface
12. Treatment and control:
Do not irrigate with overhead sprinklers.
Ensure balanced nutrition and avoid high nitrogen
fertilizattion.
Wettable sulphur, sulphur dust, or lime sulfur as well
as potassium bicarbonate is helps to control the
disease.
Sometimes backing powder, neem oil extracts and
soap solution can be useful.
