Potato Blight

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At this time of year Potato Blight can strike. This devastating plant is disease due to a fungus that spreads in the air. When it lands on the wet leaves and stems of potato and tomato plants it enters them and quickly kills them off. If left unchecked the fungi fall to the ground and infect the tubers turning them into an inedible mushy mass.

When does it happen?

The key thing is to be on the look out for it and catch it early. Usually it only appears when it is fairly warm - when the daily temperature is never below 10ºC and when we have had high humidity and rainfall for at least two days. .

What to look for?

The next thing is to check your plants for evidence of attack. In the early stages blight can be confused with other things such as other fungal infections, the natural die back of plants ending their growth period and magnesium deficiency. Here is a website with details of what to look for on the leaves and stems.

I have found that outdoor tomato plants get them first as they have very little resistance – so they act like an early warning sign! In the past many varieties of potatoes had resistance to the blight fungus but with time a new variety of fungus emerged and older potato varieties have much less resistance to this new form. However some blight resistant potatoes are now available.

What to do about it?

If you find a few blighted leaves cut them off and dispose of them. If you have a dry period it may stop the blight in its tracks as it needs to land on wet leaves to spread.
However if the damage is extensive then the only answer is to cut off the potato stems at the base and dispose of them. This stops the fungus spreading to the tubers. You may have a reduced crop but at least you will have some potatoes this year!