TOMATO AND POTATO BLIGHT ALERT – with organic management tips
for anyone who lives where it has been raining rather a lot lately. All this dampness, combined with cool temperatures, creates a perfect environment for the spread of Late Blight, Phytopthera infestans.
Just to refresh your memory, that’s the disease responsible for major crop devastations from the Irish potato famine of the 1840s to the Eastern US tomato catastrophe of 2009.
Although Late Blight isn’t a fungus, it’s like a fungus in that once you’ve got it, you’re cooked.
The only “cure” is prevention:
- Choose diverse varieties, including several cherry tomatoes, which seem to be more blight-resistant.
- Space plants wide apart for good air circulation
- Remove lower leaves, then mulch with straw to help prevent splash up of soil borne diseases. Though (usually) less devastating than late blight, these weaken the plants and make them more blight-susceptible.
- Feed once a month with quarter-strength fertilizer (heavily diluted fish emulsion and seaweed) to promote health without encouraging excess growth of tender, vulnerable stems and leaves.
- Spray regularly with organic fungicide – it only works if it’s on the leaves when late blight spores come calling.
More on late blight and its organic management – from Kentucky State University, as it happens, but equally useful wherever you are – is here.