Agriculture Reference
In-Depth Information
Management
•
Plant on well-drained soils.
Spray with recommended fungicides.
•
Prune vines to reduce density and allow better spray
penetration.
•
Develop a grass sward under the vines to reduce
contaminated soil splashing on to vines.
•
Graft to
Phytophthora
-resistant rootstocks; high grafting
(at least 30 cm) will reduce soil splash onto the stems
of the susceptible scion.
•
SCAB
■
Cause
The fungus
Cladosporium oxysporum
.
Fig 15.16 Advanced scab symptoms on fruit.
Symptoms
Small, circular, translucent spots develop on leaves and
young shoots, becoming covered with grey, powdery
masses of spores. Infected leaves fall readily. Lesions on
older leaves may develop a shot-hole appearance. Similar
spots may form on fruit with the tissues beneath growing
into hard, raised scabs up to 5 mm wide. Badly infected
fruit may become deformed.
Source of infection and spread
The fungus survives on decaying plant material. Spore
dispersal and disease development are favoured by cool
(19-25°C) moist weather. Spores are spread by wind and
water splash.
Importance
Scab can cause serious losses in cooler regions during wet
weather.
Management
•
Prune vines and spray with appropriate fungicides.
Plant resistant varieties.
•
Fig 15.15 Scab lesions on green fruit. Inset: severe symptoms on
mature fruit.
Fig 15.17 Scab on passionfruit flowers.
