Control measures

Slugs need to be controlled throughout the rotation, mainly by intercropping management but also with a series of preventive measures required once the potato crop is established. These methods are summarised as follows:

Intercropping soil management

• destroy the straw after the harvest of the grain crops; an initial and superficial soil operation as soon as possible after the grain harvest, ideally prior to a dry period;

• incorporate harvest residues in order to prevent “hollow” soils;

• limit the green manure period to a minimum and facilitate its decomposition by a soil incorporation prior to ploughing. In general terms, limit all food sources for the slugs during winter (groundkeepers, inadequately incorporated green manure, etc.).

Planting and monitoring the potato crop

• avoid planting potatoes in heavy soils, these are favourable to slugs; avoid the proximity of compost heaps or piles of organic waste, as all of these provide a base from which the slugs will carry out their midnight raids;

• carefully prepare the soil before planting, in order to bring eggs to the surface so they will be eaten by birds and later to limit the slug movement. In a high risk situation, select potato cultivars showing resistance or low attraction for the slugs and avoid late maturing cultivars; 

• adapt chemical control to the presence of the slugs by monitoring “slug activity” with the use of traps especially at the high risk period of tuber enlargement stage;

• keep irrigation to a minimum;

• reduce the delay between haulm destruction and harvest.