Now we need to mention pests and diseases which are fully described in my book, The Peoples Potatoes. The key point is that a healthy soil and plant will go a long way to limiting damage and crop loss. It is essential to have the foliage come through the ground evenly in colour and growth, with many stems and quick development forming a bushy, not elongated plant. All the leaves should be a dark or lime green and there should be no sign of crinkled leaves that could indicate poor seed health.
Potato blight is the most popular plant and tuber trouble. The plant is susceptible to attack in prolonged periods of muggy, wet and damp weather. The following points may be helpful in minimising the environment for blight attack:
• Ensure air can travel through the crop
• Plant with wide spacing and wide rows
• Use a potato fertiliser with high potash element
• Remove any volunteer potatoes form last year
• Variety choice! (Use earlies or second earlies if all else fails but also check out the blight resistance of each variety. Some like those prefixed “Sarpo” have excellent blight resistance. Spraying with copper sulphate may also give some protection)
Slugs are another cause of crop destruction. Again there is much the gardener can do:
• Remember that heavy soils are more prone and should be dug a few times before planting
• Encourage birds and hedgehogs
• Ensure the rows are thoroughly banked up (ridged) and the surrounding area is kept clean and tidy with no damp areas that attract slugs
• Again, variety choice is key with varieties such as Maris Piper being the most susceptible and Kestrel the least
• Slug pellets are useful but rarely prevent the underground kneeled slug
Potato Cyst Nematode can be a real nuisance and is usually caused by short rotations. Keep the soil healthy (lots of organic matter) grow brassica in the rotation and again variety choice is key to managing this.
If the plants look crinkled it’s usually down to a virus in the seed. Note the seed source and avoid that outlet next year. On new ground tiny holes in the tubers can be from wireworm and this will disappear the following year on a well dug bed. Large holes in the tubers on newly dug ground are from the chafer bug. Unlike the slug they eat one tuber at a time so damage is not usually total.
Now that the plants are above the ground, the tubers will form and this happens when the plant is very young. A rainy season will imitate more tubers than a dry season so keep varieties like Kestrel well-watered in the early stages. Bank up the row to avoid tubers turning green if protruding, minimise blight infection, lower slug damage and keep the plant stems from breaking in strong winds.