The general methods of control are:

(A) Eradication of alternate and collateral hosts.

(B) Alternation in maturing practices.

(C) Use of chemicals and antibiotics.

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(D) Breeding of diseases resistant varieties.

(1) For Rust Control: (Caused by Puccinia sp.):

(A) Eradication of alternate and collateral host is an important method where the rusts penetrate on them. In India the problem is of over summering on stray or self-sown wheat plants and other collateral hosts on the hills. If these sources could be destroyed during the summer months the inoculums for the outbreak of rusts in the plains during the following winter would get greatly reduced. Also, if only rust resistant varieties could be grown in hills it would greatly solve the rust problem in the plains.

(B) Alternations in maturing practices:

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It has been found that susceptibility to rusts increases with nitrogenous fertilizers and decreases with an application of potash fertilizers so an alternation in the fertilizer pattern is called for the proportion of nitrogen in N-P-K fertilizer ratio should be reduced in order to reduce the incidences of rust in a susceptive variety,

(C) Chemical Control:

An application of sulphur dust is found to be effective in controlling the incidence of rust, the proportion should be 30 pounds of fine sulphur dust per acre at 4-day intervals during the period when rusts usually occurs on the crop. Others recommended chemicals are nabam and zinc- sulphate, Dithane D-14 or Dithane M-45. Certain sulpha compounds like sodium-salts of sulphadiazine, sulphapyridine have also been found to be effective.

(D) Breeding of rust resistant varieties is a very useful method of control. Systematic breeding of such varieties was started in 1935 but it has been a difficult task to find a variety resistant to all the three types of rusts and also the increase in the physiological race flora causes complications.

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(2) For Red Rot Control: (caused by Colletorichum falcatum)

(A) Field sanitation is one of the important measures to check the building up of the inoculums and thus preventing an epiphytotic infection.

(B) Use of healthy sets for raising a new crop. The sets should be selected from healthy canes (and those showing any reddening of pith should be rejected.

(C) Rationing should not be permitted especially when the disease is known to be present in the locality.

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(D) Rotation of crops should be practices in order to minimize soil-borne infection. A rotation of 2-3 years has been found effective.

(E) Use of disease resistant varieties is the best method of control.

Fungicides Used for Control Measures:

Copper, sulphur, organo-mercury and organo-sulphur compounds and antibiotics are some of the important fungicides. Recently some systemic organic compounds have also been developed. The choice of fungicide depends on the nature of disease and on the suceptibility of crop. They are available as dusts or wettable powders and sometimes in liquid forms. The method of applying them depends on the availability of water, suitable machinery, the nature of the crop to be treated, the area to be covered and the cost of labour.

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Copper Fungicides:

Bordeaux & Burgandy mixtures are the dispersible forms of cuprous oxide, copper oxychloride and basic carbonates are among the important copper fungicides. For preparing 5:5: 50 Bordeaux mixture, 2 kg of copper sulphate and 2 kg of quicklime are dissolved in 225 litres of water. At first the stock solution of the two constituents (Vz kg in 4 litres of water) are prepared. Bordeaux mixture deteriorates on standing hence only fresh preparations are used. Addition of 60 g cane-sugar per 225 litre prevents deterioration.

Burgandy mixture is a variation of Brodeaux mixture in which lime in replaced by sodium carbonate (washing soda). The method is same. The usual strength of solution is 4-6¼ -50. There are a number of proprietary copper fungicides available in the market, e.g. Perenox, Penelan, Blitox, Cuprojcyt, Cuprosan, Fytolan, which are as efficacious as, and in some cases better than Bordeaux mixture. The proprietary products also contain dispersing and wetting agents which make them more effective.

Sulphur Fungicides:

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The important sulphur fungicides in use are sulphur powder, wettable sulphur, lime sulphur and organo sulphur. Sulphur dust is a very cheap fungicide but its efficacy depends upon the size of the particles which should pass through a sieve of 250 to 300 meshes per inch.

Wettable sulphur is used on crops which are liable to suffer from lime- sulphur scorching. The lime sulphur spray should not be used on tender foliage as it is likely to scorch it. A number of organo-sulphur compounds e.g. thiram and dithiocarbamates are extremely safe to use on most of the plants with tender & sensitive foliage. Tulisan, Zineb, and Ziram are some of the proprietary products, based on organo-sulphur compounds.

Organo-Mercurials Fungicides:

These have proved to be effective in controlling weed borne and soil-borne diseases. They are applied as dusts in extremely small doses to the seed before sowing. They have no harmful effect on germination.

Rather, they prevent emergence losses caused by soil-borne pathogens and result in a better stand of the crop. e.g. Agrosan GN, Ceresan, Semesan and Perrugen. Great care is taken for handling these. Linseed and some vegetable seeds are non-tolerant to mercury. In the recent years, certain chemicals such as captan, Thiram, Busan-72 and Dithane M-42, and some systemic fungicides have been developed. They may be used for seed treatment instead of the mercurials.

Systemic Fungicides:

These can move mainly upwards only within the plant and kill the pathogen away from the point of application. They can be applied as seed or soil treatment, and as sprays. Some of the important systemic fungicides are Oxathin., derivatives (Plantvax & Vitavax), Benlate, Demosan and Bavistin.

Antibiotics:

Antibiotics are mainly used against bacterial plant pathogens. Some of the promising antibiotics are streptomycin sulphate, streptomycin, terramycin, agrimycin-100 (a mixture of streptomycin and tetracycline), agrimycin-500 (containing copper) etc.