What is potato blight?
Potato blight is a fungal disease caused by organism Phtophthora Infestans.
In warm and humid conditions, it spreads in the air rapidly through foliage and can infect tubers causing rapid rotting.
Infection can easily destroy a crop, and tubers can be under threat for long periods.
What blight looks like
Initial symptoms: small dark spots on leaflets, often surrounded by a light green halo.
Subsequent symptoms: fine white downy growth around the edge of the lesion. This is the fungal fruiting growth. At this stage, the fungus is producing millions of spores.
Final symptoms: brown dying foliage and stems. Spores can be washed down into the soil to infect tubers. Once tubers are infected, they will develop soft rot by invading bacteria, a foul smelling putrid mess.
What to do
- Chitting (producing shoots from seed in the light) reduces emergence time and canopy development. This helps as foliage, is more susceptible during growth phase.
- Watering crop at the base, NOT the foliage, will reduce humidity around the foliage. Mulching will reduce the need for frequent watering.
- Mix varieties in alternate rows with the highly resistant varieties (eg. Sarpo Mira).
- Use only Safe Haven certified seed potatoes (do not use harvested tubers from previous crops).
- Always check foliage regularly, particularly in humid weather. At first sign of infection, remove infected foliage and burn.
- Do not compost infected foliage or tubers. Spores will remain active in the heap.
- Crop rotation. Remember, tomatoes and potatoes are from the same family.