Dumping off
Research shows that at least five per cent of all seed sown are lost to pre-emergence damping off while at least thirty per cent of all seedlings transplanted are lost to post-emergence damping off. The unfortunate thing is that it affects multiple crops across hybrid and open-pollinated varieties.
The good news is that it becomes less of a problem as the host plant grows. However, if the damage is not managed well, it can cost the farmer a fortune due to death of the seedlings in the first two weeks.
There are two types of damping-off which are post-emergence damping off and pre-emergence damping-off.
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Pre-emergence damping-off is generally caused by the invasion of the host by the fungus before plant emergence from soil. This is due to conditions that inhibit or slow seed germination while allowing the pathogen to grow.
Post-emergence damping-off occurs on young seedlings at or near the soil line, although, the fungus, may infect the roots or root hairs.
SYMPTOMS
The host tissue appears water-soaked and constricted, eventually leading to seedling collapse.
Damping-off becomes less of a problem as the host plants mature.
Infected stems may be somewhat smaller in diameter than normal, but tough and wiry; hence, the name “wirestem.” This disease is most problematic on slow-growing and deep-seeded plants.
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CONDITIONS FOR DISEASE DEVELOPMENT
These fungi may be present in the soil for a long time, but will not generally affect plants until the right environmental conditions, such as wet soils and cool temperatures, are met. Disease damage is generally greater in soil with infected, non-decomposed plant debris.
HOW TO CONTROL
- Fumigate, manage irrigation water and rotate to non-hosts to help reduce inoculum levels.
- Sow a fungicide-treated seed to help control these pathogens that cause pre-emergence damping off
- Spray with a fungicide like Redomil gold on the eve of transplanting to prevent post-emergence damping off.
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Reference: Seminis
