Agriculture Reference
In-Depth Information
Fig 6.11 Blighting and blackening of young shoot caused by alternaria
brown spot.
Fig 6.14 Corky, cracked pockmarks resulting from brown spot lesions
that have dried out.
Fig 6.12 Branches affected by alternaria brown spot. Note the twig
dieback and leaf distortion.
Fig 6.15 Alternaria leaf spot on leaves of a rough lemon seedling
rootstock. Leaf spots are surrounded by chlorotic tissue and the toxin
produced by the fungus causes the veins to brown.
Source of infection and spread
The fungus sporulates on dead host tissues. Large numbers
of spores are produced and are spread by wind and water to
infect young leaves and fruit. Ideal conditions for infection
are 12-14 hours of leaf wetness at 21-27°C. In the case of
centre rot, spores that commonly lodge in imperfections
Fig 6.13 Alternaria brown spot on mandarin fruit.
