Blight

Mention the word blight to any potato grower and you'll hear the collective intake of breath across the country. Blight is the scorge of potato growers and is common on allotment sites. Spread through the air, once your potatoes become infected there is little you can do help them.

There are two types of blight, early and late, and it is the late type that is prevalent in this country. Caused by humid, damp conditions blight strikes around August/September and can linger until the first frosts. Rain can wash spores from plant to soil, these can then be transported on the soles of your wellies to other parts of your allotment. So its important to ensure that you wash your wellies if you are working in a blight affected part of your allotment, before walking to another. Especially avoid going into the greenhouse as blight affects tomatoes too (they are related to the potato).

Identifying blight can be difficult as there are many other types of fungus that can affect plants, not all of them are as severe as blight. Below are some images of blight affected potato plants. Black spots appear on the leaves at first. On the underside, this spot is usually surrounded by a ring of white mould. Over time, the stems become black. On the potato crops themselves, blemishes (black, purple or brown) are noticeable on the skin, and when cut, brown squigly lines are visible. Blight infected potatoes will rot if stored.

Click on each image for a closer look.

This leaf has a brown spot, indicating blight.

On the underside of the same leaf, the brown spot is circled with white mould.

These leaves show more brown spots, while one has curled and died.

 

You can find more information on potato blight and possible prevention by clicking here.