Conrol of Potato Blight - Phytophthora infestans
Potato blight is caused by a fungus, (latin name - Phytophthora infestans), which spreads rapidly in warm, moist conditions.
Dark brown patches and yellowing appear on the leaves, which turn black, before a white bloom develops on the underside as the foliage dies. The white bloom is made up of the fungal spores which are then blown by the wind and spread the infection. The leaves die off, and tuber growth stops. The spores drop onto the tubers in the ground and cause them to go brown and rot. The potatoes, and the whole area, smell rancid and rotten.
Vegetable gardeners should avoid, prevent and delay the onset of blight by:
- using good quality, blight-free potato seed
- growing blight resistant varieties
- aiming for early harvest, before blight becomes a problem
- chitting, to bring harvest forward
- planting as early as possible, to bring harvest early
- mixing varieties, as some are more prone to blight than others
- avoiding sheltered positions, as blight thrives in humid areas
- practising good vegetable garden hygiene - tidy away all waste potato haulm and tubers & burn. Do not leave on the compost heap. All tiny potatoes & damaged tubers must be lifted from the ground, & thoroughly harvested. If not, they will grow the following year (volunteers) and act as a host for blight. All volunteers must be removed as soon as seen
- watching neighbouring potato plots to make sure they have not got blight
- spray with a preventative fungicide every 14 days once the leaves have met in the row
- watch the weather and listen for blight warnings & Beaumont periods
Once blight has been seen:
- remove the leaves and burn them
- lift potatoes as soon as possible - but leave those which actually had blight for 14 days, to avoid spreading the spores onto the tubers and causing them to rot in store.
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