PAPAYA (PAPAW) - Diseases of Fruit Crops in Australia - page 184

Fig 14.4 Cut papaya fruit showing dark water-soaked areas
of infection.

Fig 14.2 Dead crowns of trees infected with bacterial decline (left)
compared with healthy trees.

Source of infection and spread
The bacterium is spread by water splash and wind-
driven rain. Insects may also be capable of spreading the
pathogen as they move from plant to plant.

The bacterium survives in lesions on infected plants
and as an epiphyte on the leaves of species other than
papaya.

Importance
Sporadic outbreaks of canker and decline diseases of
papaya caused by Erwinia have been reported from
Indonesia, the Pacific area and the Caribbean on several
occasions since the 1930s. However, recent outbreaks on
the west coast of the Malaysian peninsular appear far
more serious with considerable spread of the disease
since its detection in 2003 and the loss of more than
one million trees.

What to do if you suspect bacterial decline
or crown rot
This pathogen is a biosecurity risk to Australia. Any
suspected affected plants should be reported to the
nearest Department of Primary Industries or the Plant
Health Australia hotline [phone]).

Fig 14.3 A papaya plantation devastated by bacterial decline.

Symptoms
The disease first appears as small, angular, water-soaked
spots on the leaf blade. These later become light brown in
colour, translucent and enlarge to 3-6 mm in diameter. The
spots may coalesce to form large, irregular, necrotic areas.

BACTERIAL LEAF SPOT

■ Cause
The bacterium Pseudomonas caricapapayae .