Seed Treatment

the disinfecting of seeds and seedlings with seed-treating materials to protect plants against fungous, bacterial, and viral diseases at the beginning of growth and development. Seed treatment also prevents the penetration of pathogenic microorganisms into seed tissue during storage, increases sprouting and germinating capacity, and eliminates the transmitting of disease by seeds.

Seed treatment may be wet, dry, or semidry depending on the structure and degree of infection of seeds and seedlings, the characteristics of the microorganisms involved, and the properties of the seed-treating materials. With wet treatment, the seeds are soaked with a solution of the treating material, usually formaldehyde, and are covered with burlap or canvas and cured for two hours, after which they are dried. This is a labor-consuming process and is used only to treat small batches of seeds of valuable strains of wheat, barley, and millet that are infected by smut.

With dry treatment, the treating material is applied to the seeds or seedlings in the form of a dust. This method is used to disinfect seeds of tubers and grain, vegetable, industrial, bulb, and root crops. The drawbacks of dry treatment are the relatively low adherence of the materials to the seed surface and their tendency to disperse, which causes poor working conditions in terms of sanitation and hygiene.

Semidry treatment of seeds involves the application of a dust to moistened seeds or the treatment of seeds with a suspension obtained by mixing a powdered seed-treating material with water. The quantity of water for moistening the seeds or of the suspension containing treating material is 5–10 liters per ton. Adhesives are added to the water for better retention of the seed-treating materials on the seed surface. Such adhesives include concentrates of sulfite waste liquor, silicate glue, flour paste, starch syrup, and skim milk. Abroad, variations of semidry treatment include the slurry method, in which seeds are coated with a thick suspension of the treating material, and the panogen method, in which solutions of organo-mercury compounds are applied to the seeds in a proportion of 200 ml (milliliters) per 100 kg of seed. Semidry treatment is used to protect seeds of such gramineous grain crops as oats and barley against smut. It is the most desirable method since the seeds do not have to be dried (their moisture increases by only 0.5–1 percent) and sanitation is easy to maintain.

Heat treatment is another commonly used method of disinfecting seeds. With this method, causative agents of disease in seeds are killed by means of air heated to 40°-90°C or hot water at 50°-60°C. This method is used primarily to protect wheat and barley against loose smut when the causative agent is located deep in tissues of the seed and cannot be killed chemically without harming the seed’s potential for development.

Special machines, devices, and attachments are used for seed treatment. The least effective time to treat seeds and seedlings is on the day of sowing or transplanting, and the most effective time is five to eight months in advance. Special clothing is worn during seed treatment. The work is done in an open area or under an awning and must not be carried out closer than 200 m from human and livestock housing and sources of drinking water. The workday should be no longer than four hours.