Sarah O’Neil resolves issues that may crop up now it's potato planting time.
BROWN SPOTS & BLOTCHES
Issue Fast-spreading brown patches on leaves and stems, quickly turning the whole plant black.
Cause Blight. Potatoes are closely related to tomatoes and can suffer from blight in a similar way to tomato plants, including early blight (caused by Alternaria solani) and late blight (caused by Phytophthora infestans).
Solutions Remove affected plants straight away and burn or bin them. Wash all tools and equipment after use on infected plants. Give plants plenty of space for good airflow when planting.
STUNTED PLANTS WITH DISTORTED LEAVES
Issue Not only do plants fail to thrive but the potato can discolour when cooked and have a bitter flavour.
Cause The small sap-sucking insect tomato potato psyllid (TPP) and the bacterial pathogen Liberibacter, which the psyllid spreads, can cause serious problems for potato plants.
Solutions Protect the crop with an insect mesh barrier from the start of the growing season. Preventative spraying with an appropriate spray every 7–14 days should control the infestation. Remove and destroy affected plants to avoid spreading the disease.
TUNNELS IN TUBERS
Issue Finding tunnels in potatoes when cut open can be disappointing, but the potato is still edible once the affected parts are removed.
Causes Wireworms or the potato tuber moth.
Solutions Incorporate plenty of organic material into the soil and don’t let it get too dry. Use an insect mesh barrier to prevent access. Practise crop rotation to avoid planting in the same problem soil next season.
Issue Cutting into the centre of the potato to find a large hole in the centre.
Cause Inconsistent watering and, in particular, a prolonged wet spell after dry weather.
Solution Ensure even watering during the growing season – although excessive rain can’t be avoided.