Some important crop diseases and their characteristics are given below:
(i) The two common diseases of wheat are rust and smut. Both of these diseases are caused by fungi. Rust disease is characterized by the presence of brown spots on the leaves and stem. These spots latter turn black. In smut, the grains are replaced by a black powdery mass of spores.
(ii) The two common diseases of the rice crop are blast and root rot. The blast disease is characterized by spindle shaped lesions on leaves, darker grains and routing of neck leading to dropping of ears. The second disease, the root rot, is restricted to nursery and is characterized by stunted growth of seedlings, yellowing of leaves and brown discoloration and rotting of roots. Another disease of the rice crop is bunt. In this disease grains are transformed into a black sooty powder.
(iii) The rice crop is also attacked by many insect pests such as Gundhi Bug and Tissue Borers. Gundhi Bug attacks the tender rice grains and sucks their sap. The affected earheads remain without grains.
(iv) The cotton crop is attacked by Boll-worm insects. These insects attack the crop by boring into flowers, buds and boils.
(v) Late light is a fungal disease of potato crop.