BOTANY Higher Secondary Second Year - Textbooks Online

Pathogen
The mycelium of Cercospora personata is brown, septate branched
and slender. Branched haustoria are produced to absorb food materials
from the host tissue. The conidia are long and septate. Each conidiophore
produces single conidium at its tip. The spread of the disease takes place
by means of conidia which are dispersed by wind.
Black lesions
Control
The disease can be controlled by sanitation and crop rotation. The
use of phosphatic and potassic manures reduce the disease. Sulphur dusting
is quite effective. Resistant variety should be sown.
Pathogen
Citrus canker
Disease due to a bacterium Xanthomonas citri. This bacterium is of
bacillus and gram negative type. In India, this is the most commonly
prevalent disease during the rains.
Symptoms
The disease affects the leaves, twigs, thorns and fruits. All green
parts and maturing fruits become more or less covered with brown scabby
spots surrounded by dark – brown glossy margins. The lesions may
enlarge to a diameter of 3 or 4 mm become raised and rough and turn
brown. The bacteria enter through the stomata and wounds and multiply
in the cortex to which they are confined.
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Conidia
Fig. 6.1 Tikka disease of groundnut