AGRICULTURE AND IRRIGATION
DISEASES OF CROPS
Of Cereals: Of jowar: Grain smut, kani or dane kani (Sphaceteotheca sorghi, Link, Clinton): The disease is noticed after the ear-heads
have formed. The grains are converted to black masses of spores. The disease generally occurs from September to November on kharif jowar and from December to February on rabi jowar. The kharjf jowar is more susceptible to this disease than the rabi jowar. The disease can be controlled by treating the seed with sulphur dust of 200 to 300 mesh at the rate of 100 grams per 30 kg. of seed.
Downy mildew, kevda (Sclerospora sorghii, Kulk, Weston and Uppal): The disease is noticed on young leaves the lower surface oi which is covered with downy white growth. Later the leaves become shredded. The disease prevails during August and September. The control measures include rouging, burning of affected plants, proper method of rotation, and growing of resistant varieties.
Ergot, chikta (Claviceps microcephala, Wall, Tal): The grains in the ear-head are transformed into black bodies called sclerotia, which contain a poison called ergotin. This poison is fatal to cattle and human beings also. The disease occurs in die middle of August and September. The grains may be soaked in water. The sclerotia and light grains which float may be removed and burnt. Only the steeped grains may be used as seeds. Deep ploughing may also be practised.
Downy mildew, gosavi (Sclerospora graminicola sacc, Schrotcs): On young leaves downy white growth mosdy on lower surface, with yellowing on corresponding upper surface is seen. On the ear-heads instead of grains small greenish scale-like growth is observed which gives the appearance of green ear. The disease occurs in the months of August and September. It can be controlled by systematic rouging, burning of affected plants, rotation, and growing of resistant varieties.
Of groundnut: Tikka (Cercospora arachidicola Hori: Cercospora personata Berks and Curs): The disease prevails during August and September. Its first sign is the appearance of conspicuous round purplish brown spots. The spots later on expand in size and become blackish in colour. Cercospora arachidicola causes formation of irregular circular black spots, often confluent, varying in size from one mm to one cm and surrounded by a yellowish zone, blending into the green. When'mature, the conidiophores emerge out on the upper surface exclusively. The spots caused by cercospora personata are more or less circular, varying in size from 1 mm. to 7 mm. dark brown to black in colour. The spots are surrounded by a bright yellow halo on the upper surface when matured. The disease is controlled by spraying the crop in the beginning of August with 3:3:50 bordeaux mixture or any copper compound. If necessary, second spraying in the fourth week of August may be given and third spraying if required, in the third week of September. Besides it can be successfully
controlled by sulphur dusting (200 to 300 mesh) at the rate of 15 lb. per acre.
Of cotton : Anthracnose, kawadi (Colletotricum indicum, Dastur): The disease appears at the seedling stage during the months of June and July, and after the bolls have formed in October and November. At the seedling stage the disease causes seedling rot, i.e., ' cotton rot'. If it appears at the time of boll formation black depressed circular spots appear on the bolls which become yellowish from
inside due to spore formation. Attack on the bolls results in stunted growth of the plants and discoloured lint which fetches lower price in the market. The disease can be controlled by destroying the affected debris, by sowing healthy seeds and by treating the seeds with organic mercurial compound containing 1 per cent organic mercury, at the rate of 2 to 3 grams for one kilogram of seed.
Black arm or angular leafspot, tikkya or karpa (Xanthomona-malvacearum, Smith Dowson): The disease occurs on rain-fed crops in July and December, and on irrigated crops in March. The disease first manifests as small water soaked areas on leaves which are angular in shape. These spots later coalesce involving longer areas of the leaf. The petioles, stem and bolls also get affected. Mature bolls, when affected open prematurely and the lint from such bolls gets yellow stains. The American cotton variety is highly susceptible. The disease can be controlled by growing resistant varieties, by treating the seeds with organo-mercurial compound, and by spraying the crop with bordeaux mixture 3:3: 50, two to three times during the life of the crop.