LYCHEE - Diseases of Fruit Crops in Australia - page 148

DOWNY BLIGHT - BIOSECURITY THREAT

Cause
The oomycete Peronophythora litchii.

Source of infection and spread
The disease is favoured by cool, wet weather and can
spread rapidly in these conditions. Sporangia produced
on the surface of diseased tissue are spread by rain
splash; zoospores are liberated from the sporangia in
cool wet conditions and infect host tissue through direct
penetration.

Symptoms
Symptoms include a brown blight that affects immature
and ripe fruit, leaves, f lowers and pedicels. During moist
weather, the lesions may be covered by white growth
(hyphae, sporangia and sporangiophores). Infected fruit
may fall prematurely. Importance

Downy blight is present in China, Taiwan, Thailand and
Vietnam and can cause significant losses, especially
during extended wet, overcast periods. This disease is
not present in Australia and is of quarantine concern.

Observe quarantine regulations to prevent this disease
from entering Australia.

What to do if you suspect downy blight
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 10.7 Downy blight caused by Peronophythora litchii .

FURTHER INFORMATION

■ C o a t e s L M , Z h o u E & S i t t i g u l C ( 2 0 0 5 ) D i s e a s e s . I n Litchi and
Longan: botany, production and uses. (Eds CM Menzel and
GK Waite) pp. 261-272. CABI Publishing: Wallingford.

Coates LM, Sangchote S, Johnson GI & Sittigul C (2003) Diseases of
Longan, Lychee and Rambutan. In Diseases of tropical fruit crops .
( E d . R C P l o e t z ) p p . 3 0 7 - 3 2 5 . C A B I P u b l i s h i n g : W a l l i n g f o r d .