Common diseases caused by the above mentioned agents are
This is the drooping of the foliage and ultimately
death of the plant. It is caused in seedlings when their bases become rotted due
to fungus and fall on the 0ground. e.g. shisham. The only control measure that can
be applied is selection of a well-drained site.
It is a definite, localised deformation (necrotic
lesion) formed mainly in the bark. It results in the death of the part of the tree
above the canker. Cankers are caused by frost, sun scorch, fire and drought.
It is the decomposition of wood by fungi. When they
attack living tissues, they may kill the trees. When they attack the dead wood (as
the heartwood) they cause rot or heart rot.
Heart rot :
It is caused by a number of fungi. The presence
of fruiting bodies of the heart rot fungi, punk knots, swollen knots, dry branch
sticking out of bole and swollen boles are indications of heart rot in trees. Injury
to trees should be kept to a minimum to prevent heart rot.
Diseases in roots of trees are caused by root infecting
fungi which may be soil-inhabiting or root-inhabiting. The soil-inhabiting fungi
causes wilt in trees eg shisham. The root-inhabiting fungi causes root rot in trees
eg shisham and khair. The roots of new seedlings receive infection from old infected
roots in the soil.
Damping off is one of the most serious of all nursery diseases. Mortality
occurs at three stages of growth of seedling - the seedlings
may be killed even before they emerge above ground level due to pre-emergence blight;
or the seedling may get killed after emergence from the ground as a result of rotting
of tissues at the base; or older seeds may die due to root-rot. The disease can
be controlled by raising nurseries in good sites (it should be located in a well
drained site with light textured soil without overhead shade) and fungicidal treatment
of seed and soil before and after sowing.