Potato Blight is a problem when growing potatoes. Blight is an air bourne fungus type disease which attacks the foliage (and later the tubers) causing it to collapse. It commonly occurs in wet, mild and humid conditions and is difficult to manage. Blight can affect tomatoes as well, although if grown in a greenhouse this will afford protection as it is mainly, but not exclusively, a disease which affects out door crops. Blight starts with brown marks on the leaves, image left and quickly spreads so that all the foliage turns brown or black collapses and the plant looks patently sick; it cannot be missed. Once it takes a hold, there is not much that can be done as it spreads rapidly.
Good air circulation can help. Whenever space allows, do not plant the tubers too close together. In addition, follow crop rotation because the fungus can overwinter in any tubers left in the soil and the virus can spread from there. This is why when clearing the veg plot at the end of the season, it is important to remove all potatoes, including any tiny ones.
You can grow Blight resistant potato varieties, which does not guarantee that Blight will not visit, but much reduces the chances. The most commonly sold Blight resistant varieties is the Sarpo range. Late varieties of potato are more prone to blight. Earlies and salad potatoes may escape as the warmer humid temperatures which are more likely later in the year. In the eastern parts of the UK and drier areas, it is less of a problem, which may be why a lot of potatoes are grown in Lincolnshire. It is the humid, warm air which allows the pathogen to spread, and it can destroy a crop in a couple of weeks.
If the plant becomes badly infected, the only possibility is to cut off all the infected leaves close to soil level and be careful to pick up all bits of infected leaves. If the blight has not reached the tubers, they can still be harvested.
Potatoes also suffer from keeled slugs which live underground and bore into the tubers, which damages them and makes them prone to rotting. Because this form of slugs lives so far underground slug pellets are not effective, nematodes are a better suggestion.
Potatoes can get scab which makes them look unattractive, but they are edible and not noticeable when peeled. This tends to be more of a problem on thin chalky soils, which are prone to drying out the addition of organic matter will reduce the risk of scab.