Fungal spores or bacteria can infect seeds while they are still developing on the plant or after the harvest. These pathogens will then cause diseases in the next crop (seed-borne diseases).
To protect against seed-borne diseases several types of seed treatment can be used:
Hot water treatment
Spores or bacteria that are attached to seeds can be killed by soaking the seeds in hot water. Use water of exactly 50°Celcius and soak the seeds for 30 minutes.
Chemical seed treatment
Seeds can be treated with chemical fungicides to kill the spores that are present on the seed. This gives also some protection against spores present in the soil (soil-borne diseases) during the germination.
As only very small amounts of chemicals are used, this method causes little damage to the environment.
Instead of synthetic fungicides, also certain botanical extracts can protect seeds from soil-borne diseases (botanical seed treatment). For example, seeds can be treated with juice of garlic.
While chemical or botanical seed treatment only sterilizes the surface of the seed, hot water treatment can also kill germs that are present inside the seed.
Biological seed treatment
Antagonistic fungi or bacteria can be used to protect seeds. Examples of these biological agents are Trichoderma sp. (an antagonist fungus) and Bacillus subtilis (a bacterium).
An advantage of biological seed treatment is that they multiply in the soil. Therefore, even after germination, they provide protection of the root system against soil-borne pathogens (e.g. damping-off).