AGRICULTURE AND IRRIGATION

DISEASES.

Jowar.

Grain smut, kani or dane kani (Sphacelotheca Sorghi, Link, Clinton): This disease cannot be detected until the earhead comes out. The diseased earheads do not form the normal grains, instead they form spore sacs in place of grains. The affected ovaries turn into conical porcelain white sori which contain black powder consisting of millions of chlamydospores of the fungus.

In its severe attack the disease causes about 5 to 10 per cent damage to the crop. The kharif jowar suffers from the disease generally during the period between September and November and rabi jowar from December to February.

The disease usually spreads at the threshing-yard. It can, however, be controlled by treating the seed with sulphur (300 mesh fine) at the rate of 100 gm per 30 kg of seed.

Loose smut, kajali (Sphacelotheca Cruenta Kuhn, Potter): The symptoms are nearly the same as those of grain smut of jowar. The only difference being that in case of loose smut the wall of spore sac gets ruptured and black mass of chlamydospores is exposed giving blackish appearance to the affected earhead. The disease reduces the yield of grain by about 5 to 10 per cent.

The seed treatment with sulphur (300 mesh fine) at the rate of 100 gm to 30 kg of seed controls the disease effectively.

Leaf rust, tambera (Puccinia hordei coke) Reddish brown pustules are seen on the leaves of the affected jowar crop. These pustules later on let out red mass of uredospores which afterwards turn black. The damage caused by the disease amounts j to 5—10 per cent. Use of resistant varieties is the only effective way of controlling the disease.

Downy mildew, kevada (Sclerospora sorghi, Kulk): On young leaves downy white growth mostly on lower surface with yellow-| ing on the corresponding upper surface is seen. Later the leaves become shredded. The damage due to this disease comes to about 3 to 10 per cent. Systematic rouging and burning of affected plants help in checking the disease.

Wheat.

Black stem rust, tambera {Puccinia graminis, tritici, Erike and, E. Henn.): This is a very disastrous disease which in its severe attack reduces the yield of the crop by about 60 to 75 per cent. The disease appears as reddish brown elongated, linear eruptive spots known as pustules mostly on stem and also on leaves. The pustules when rubbed effuse a brownish powder which contains spores called uredospores. Later in the season, the endophytic mycelium gives second type of black coloured sori or black pustules at the same erupted spot or side by side. The black pustules contain blackish powder consisting of spores called teleuto-spores meaning last spores. As the name signifies teleuto stage appears at maturity.of the crop. This disease occurs during the period from November to February. Growing of resistant varieties, viz., Kenphad-25, MED-345, KCN, Hy-65, NI-315, NI-146, NI284-S, NI-28, NI-62, for irrigated crop and Selet-tion-59, and 125 for dry crop helps in avoiding the incidence of the disease.

Loose smut, kani or kajali (Ustilago tritici, pers, Roster.): The disease affects every part of the earhead especially the rachis, and awns and loose blackish powder is formed in place of grains. This blackish powder consists of the spores of the fungus. The disease prevails from January to March. The infection in this case being inside, seed dressing with fungicides is ineffective. The following method however is evolved to check the disease.

The seed is first soaked in cold water from 8 to 12 in the morning during the first fortnight of May. It is then spread on galvanised iron sheets in hot sun for about four hours and then stirred periodically. Subsequently the seed is dried in shade. After drying insecticides, viz., pyrethrum, D.D.T., etc., are applied to the seed which is then stored in gunny bags.

Paddy.

Paddy blast, karpa (Piricularia Oryzae Cav.): The disease first manifests on leaves as small spindle shaped brown spots with white centre on seedlings. These spots grow in size, coalesce with each other and the plant dies subsequently. If the attack is at the time of emergence of the earhead then the necks get rotten and turn black. Such heads may not develop grains. If the attack is at post formation of grains, necks do not support the weight of the panicle and it breaks resulting in grain shedding. The disease usually appears in the months of July and August.

Following are the measures which are mostly adopted to control the disease.—(1) Seed treatment with organo mercurial seed dresser containing one per cent organic mercury at the rate of 100 gm for 30 kg of seed. (2) Before transplanting, seedlings should be dipped in bordeaux mixture. (3) Before flowering time one or two sprayings of bordeaux mixture 3:3:50 or any copper compound containing 50 per cent metallic copper could be given. Besides, early Ambemohar, 39, Kolhapur scented. Patani-6, Bhadas-78, Krishnasal 10, Antarsal-10, 90, 200 could be sown as they are found to he tolerant to blast disease.

Bacterial blight, karpa or kad karpa (Xanthsmonas oryzae, Mueda and Ishiyama, Dowson): The affected crop bears water soaked streaks and marginal blighting with yellow bacterial ooze at the margins. The marginal blighting extends further resulting in death of the leaf. The disease causes decrease in yield by about 20 to 25 per cent. The disease generally appears in the months of August and September.

Destruction of debris of the plants after harvest, seed treatment with organo-mercimal compounds 2 to 3 gm per one kg of seed and spraying of endrin 0.02 per cent plus copper oxychloride 0.3 per cent three times at an interval of 20 days.

Helminthosporium leaf spot, tikkya:—The disease may occur at any tune during the growing period of the crop. The infected leaves of seedlings and adult plants show spots with white centre and a yellow halo. There may he sterility if the attack is at the grain formation stage. The measures mentioned under the paddy blast may be adopted with advantage to control the disease.

Tur.

Tur wilt, ubhal or mar (Fusarium oxygporium f. udium): —The affected plant appears sickly. The leaves drop down and the affected plants wither and die. If the roots of the affected plants are spat open, brown discolouration of the vascular tissue is seen. The damage due to this disease is about 2 to 5 per cent. Growing of resistant varieties helps in controlling the disease.

Groundnut.

Tikka (Cercospora arachidicola Hori):—The disease is caused by two species of the pathogen each producing characteristic spots. The first sign is the appearance of conspicuous round purpl.sh brown spots on the half month old plants. 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 millimetre to 1 cm and surrounded by a yellowish zone blending into green. When mature, the conidiophores emerge out on the upper surface exclusively. The spots caused by cerespora. personata are more or less circular, varying in size from 1 mm to 7 mm dark brown to black in colour with the lower surface; of the spots marked with concentric stromatic rings of conidio-phores. The spots are surrounded by a bright yellow halo when mature, on the upper surface. The disease usually prevails from August to October.

Spraying the crop in the third week of July with 3:3:50 bordeaux mixture or any copper fungicide containing 50 per cent metallic copper helps in controlling the disease. The second spraying in August and the third one in the third week of September may be given.

Chillis.

Fruit rot, kavadi, (Colleiotrichum Capsoci, Syd., Butler and Bisb.):—The disease occurs in the months of November and December on dry as well as irrigated chilli crop. The fruits rot and drop down resulting in reduced yield. The loss varies from 15 to 20 per cent under severe disease conditions. The source of infection is from seeds and plant debris. Seed treatment with organo mercurial fungicides and spraying the crop three times with bordeaux mixture 3:3:50 or any other copper-fungicide from flowering onwards helps in reducing the disease.

Authracnises, kawadi (Colleiotrichum indicum, Dastur):—On seedling stage, the disease causes seedling rot, cotton rot and damping oil. On bolls black, depressed circular spots appear becoming pinkish in the centre due to spore formation. Attack on the boils results in short, immature and discoloured lint.

Cotton.

The disease appears on seedling stage during the months of June and July and on boll forming stage in the months of October and November.

The destruction of affected debris, sowing healthy seeds and treating the seed with organo mercurial compound containing one per cent organic mercury at the rate of 2 to 3 gm for one kilogram of seed help in controlling the disease.

Black arm or angular leaf, spot, tikka or karpa (Xantho-monas malvacearum, Smith, Dowson):—The disease generally prevails in the irrigated and American cotton growing areas of the district. On dry cotton it appears during the period from July to December and on irrigated cotton from March to December.

The disease first manifests itself as small water soaked areas on leaves which are angular in shape. These spots later coalesce, involving larger areas of the leaf. The petioles, stems and bolls also get affected when the disease extends along the edges of mild lateral veins. It is known as black veins. Mature bolls when attacked open prematurely and the lint from such bolls gets yellow strain which is valued at a very low rate in the market. The American cotton is highly susceptible although deshi cotton is not immune.

Growing resistant varieties, treating the seed with organo mercurial compound containing one per cent organic mercury and spraying the crop with bordeaux mixture 3:3:50 two to three times during the growth of the crop help in controlling the extent of damage caused by the disease.

Grapes.

Powdery mildew, bhuri (Uncinula necater, Schw., Burr.): —. Whitish patches appear on both sides of the leaves. These patches enlarge covering maximum part of lamina turning whitish green. In severe cases withering and shedding of leaves take place. It also gives wilted appearance to the vine. The patches sometimes appear on shoots near base, which later turn black. The affected blossoms fail to set in fruit. Young berries may drop when affected in early stages and crack when affected in advanced stage. The disease occurs from November to January. In service cases the disease causes 10 to 15 per cent reduction in the yield of the crop.

Dusting the crop with sulphur (200—300 mesh) in the third week of November, December and January effectively controls the disease.

Anthracnose, karpa (Gleeosporium ampelophagum, Sacc.): — The disease manifests on vine, stems and young shoots as deep seated elongated lesions dark to the border and pinkish white, in the centre. On leaves also similar type of spots develop but later on such areas drop down. Young blossom when affected shows blighting effects but if the attack is in advanced stage on berries a peculiar symptom called blind eye spot is observed. The disease prevails during the period from June to November.

Spraying of bordeaux mixture 5:5:50 in the third week of July' and November helps in controlling the disease.

Downy mildew, kevada (Plasmopara Viticola, Berk and Curt, Berl and De-Toni):—The disease attacks all aerial plant parts, viz., leaves, canes, tendrils, bunches, etc. On upper surface the disease manifests as greenish yellow indefinite size spots, which are translucent and only in appearance. Under humid conditions white downy growth is found on the under surface of the leaf spots. Finally, they dry and turn brown. The affected leaves fall down. The disease prevails from June to September. The same measures as adopted for anthracnose can very well be tried with advantage to control the disease.

Mango.

Powdery mildew, ambya varil bhuri (Oildium mangifarae, Herthet):—On the inflorescence whitish coating appears, covering it entirely. Later on this coating turns black. The disease occurs from January to February. Spraying the tree with sulphur (200 mesh plus D.D.T. (4:1)) at the time of blossoming controls the disease effectively.

Citrus fruits.

Citrus canker, devi rog (Xanthomonas, Citri):—All aerial plant parts are affected on which a canker appears in the form of rased corky spots, orange to brownish in colour. These spots are more conspicuous on leaves and fruits. The disease causes disfiguring of the fruit resulting in reduced market prices. It persists from April onwards. Spraying the plants with bordeaux mixture 5:5:50 minimises the damage caused by the disease.

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