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Seed treatment

Seed treatment

Seed treatment refers to the application of 1. fungicide,

2. insecticide or

3. both

to the seeds to disinfect and disinfest them from seed borne or soil borne pathogenic organisms and storage insects

Disinfection here refers to the deep seated pathogens

Disinfestation refers to the pathogens outside the seed coat

Seed treatment also includes exposing the seeds to sun or washing or immersing them in water

Benefits of seed treatment

Prevention of spread of plant diseases –

both systemic and non-systemic plant diseases can be prevented by seed treatment

Examples – systemic diseases like smut of wheat, Helminthosporium blight of barley, loose and covered smuts of oats etc

Non systemic diseases that infect seed during harvest or storage period such as Fusorium with blight of barley oats, rice, sorghum etc can be effectively controlled by appropriate seed treatment

Protection of seeds –

Seed treatment protects seed from seed rot and seedling blights

Once the seed is planted the protective coating around the seed, acts as a barrier against seed borne and soil borne organisms

Improvement in germination –

Seed treatment improves the germination through the control of surface moulds and flora, which are not pathogenic but may infect the seed during moist harvesting and storage condition

Protection in storage –

It Provides protection from storage insects and pests

For complete protection it is necessary to treat the seeds with insecticides also.

Types of seed treatment

Seed disinfection

It refers to eradication of fungal spores present within the seed coat or more deep seated tissues

For effective control the fungicide must penetrate into the seed to kill the fungus

Seed disinfestations

It refers to the destruction of surface borne organisms that contaminated the seed surface but not infected the seed

Chemical dips, soaks, fungicides applied as dust, slurry or liquids have been found successful

Seed protection

To protect the seed and young seedling from organisms in the soil which might otherwise cause delay of the seed before germination

Conditions for seed treatment

Injured seeds

Seeds suffer mechanical injury during threshing, drying or processing

Any break in the seed coat offers an excellent opportunity for the fungi to enter the seed and either kill it or weaken it.

Diseased seeds

Seed may be infected by disease organisms at the time of harvest or during processing in storage

Undesirable soil conditions

Seeds are sometimes planted under unfavourable soil conditions such as cold and damp soils, which favours the growth and development of certain spores enabling them to attack and damage the seeds

Disease free seed

Seed treatment provides a good insurable against diseases, soil borne organisms and thus protects weak seeds enabling them to germinate and provide seedlings

Chemicals used for Seed treatment

A) Mercurial Compounds

Organo mercurials

used for small grains, flax cotton, and safflower

Proper dosage is critical over dosage results in seed injuring and under dosage fails to control the disease

Eg: Phenyl Mercuric acetate (PMA) Methoxy ethyl Mercury chloride (MEMC) Ethyl Mercuric chloride (EMC)

Inorganic mercurials

limited to mercuric chloride, mercurious chloride and mercuric oxide

These materials are used to treat the seeds, roots, tubers and vegetable crops

B) Non Mercurials

Organic Non Mercurials

Thiram and captan are widely used

They are less effective than the organic mercurials less damaging to the seeds and less dangerous to the persons handling the seeds

These fungicides act as seed disinfestants and or seed protectants

Over dosage is not harmful and viability is not effected

Eg: Thiram, Captan, Carbendazim, Metalaxyl.

Inorganic Non Mercurials

Copper carbonate, Copper sulphate, Cuprous oxide are the major inorganic Non Mercuric compounds used as fungicide

Copper carbonate and Copper sulphate are used on wheat for prevention of bunt diseases

Cuprous oxide prevents seed decay and damping off in vegetables

C) Insecticides

These are used individually or in combination with fungicides

Equipment for seed treatment

1. Slurry treater

A slurry is prepared by mixing the chemical with water

The treatment material to be applied as slurry is accurately measured through a simple mechanism compised of a slurry cup and seed dump pan

The cup introduces a given amount of slurry with each dump of seed into a mixing chamber where the seeds are mixed thoroughly

2. Direct treater

These are the recent ones and include panogen and Mist-OMatic treater

Of these the Misto-O-Matic treaters are widely used

The Misto-O-Matic treater applies the chemical in the form of a mist directly to the seeds

3. Drum Mixer

A simple mixer can be made by running a pipe through a drum at an angle

The drum is then mounted onto a stand

The seed and the treatment are placed in the drum and it is rotated slowly until all the seeds are corned with the chemical

4. Grain Auger

Liquid materials can be dripped on the seed as they enter a grain auger or straw conveyer

By the time seeds have left the auger the chemical is spread on the seeds

5. Shovel

Seeds are spread on a clean dry surface 10-15cm in depth

The proper amount of chemical is diluted with water and sprinkled over the seed

Mixing is done with shovel or sloop turning the seed atleast 20 times

Precautions

1. Extreme care is required to ensure that the treated seed is never used for animal or human consumption

2. Care must be taken to treat the seeds at correct dosage

3. Do not treat the seed with high moisture content as it may be injured when treated with some of the concentrated liquid products

Coloring of Seeds

Most seeds treatments contain dyes, and some companies add their own ‘colour brand’ dye to seed treatments. Dyes serve two purposes –

1. As a warning that the seeds have been treated to prevent inadvertent contamination of food or feed

2. As a visible means of evaluating the completeness of treatment coverage

The dyes, if used for treating formulation of dry seed, are mixed with fungicide and insecticide treatment

Causes of Poor Treatments

Wrong fungicides

Use of inappropriate fungicides, old dusts, etc., may prove relatively ineffective for protection against soil fungi

Inadequate dosages

Failure to get sufficient fungicide on the seed results in poor seed treatment

Carelessness

The use of the best available fungicides and the latest equipment for treating seeds does not by itself guarantee proper seed treatment

Adequate care is necessary regarding machine adjustments, etc., to treat seeds effectively