Economic Importance Plant Diseases i guess u are surprice right. Depending on climate, topography, and other factors, individual countries have emphasized production of certain commodity crops, such as coffee, rubber, citrus and other fruits, cereals, bulbs, and potatoes.
Often an important part of the economy of agricultural nations depends upon the exchange of these products for materials not grown or manufactured locally. Some Economic Importance plant diseases of international importance every rice farmer should know about.
In consequence, the regular and successful production of critical crops is essential to a stable international exchange economy.
Economic Importance of Rice Plant diseases (Oryza sativa)
Rice, which is one of the oldest cultivated crops, is becoming more widely grown; although once thought of as being principally Asiatic, it is now grown in quantity in many parts of the world.
In view of the world-wide distribution of rice and its importance as a food crop, it would be desirable to intensify the research on this cereal in order to have greater knowledge of production problems of international significance.
The rice plant is host to many pathogens, but none ever reaches the epidemic proportions of such diseases as stem rust of wheat and late blight of potatoes.
Local epidemics of rice diseases do occur, and also some of these have caused important crop losses. Research on rice diseases has been largely concentrated in Japan on the japonica types. In India where the indica types of rice predominate, and in the United States.
Economic Importance of Blast and Brown Spot
The two principal diseases of rice are blast, caused by Piricularia oryzae, and brown spot, caused by Helminthosporium oryzae. Both are known wherever rice is grown.
Blast occurs principally on the leaves and stems, especially on the neck just below the panicle, resulting in a blasted panicle. Helminthosporium commonly causes leaf blight, seedling blight, and typical necrotic spots on young and mature plants and glumes and kernels.
There seems to be little control for either disease except through resistant varieties. Blast is most common in the areas where rice is being grown for the first time, whereas Helminthosporium may occur whenever conditions are favorable. Although it is more destructive in fields grown from seed than from transplants.
Treating seed by soaking it in copper or mercury solutions or by hot water treatment has been recommended as a control measure. However, the fact that both pathogens may be internally seed-borne makes effective seed treatment difficult.
Rice is also susceptible to attack by Sclerotium rolfsii, causing seedling blight; Fusarium moniliforme, causing Fusarium blight; Xanthomonas oryzae, causing bacterial leaf blight; and several nematodes causing root rot and white tip.
Leaf smut, caused by Entyloma oryzae, has been found in southern United States, Argentina, Japan, and Philippines; and stem rot, caused by Leptosphaeria salvinii, has been reported from the United States. Southern Europe, Japan, Ceylon, and the Philippine Islands. None of these has been reported as reaching epidemic proportions on an international scale.