Wireworms, the larvae of the click beetle, can cause severe damage to potatoes (and other susceptible crops). They burrow into the tubers and render them unsuitable to be marketed for consumption. Wireworms can also cause significant damage to sugar beet, cereal, maize, legumes and various vegetables. Usually, several types of wireworms with different characteristics are involved.
In spring and autumn, the wireworms are usually found in the top soil layers, eating crop roots. In adverse conditions, the larvae retreat to deeper soil layers. In spring, the adult beetles lay their eggs into the loose, humid soil of permanent meadows and temporary grassland as well as cereals, but not in root crops. The beetles undergo a metamorphosis during 3-5 years with up to 15 larval stages. The larvae cause the most damage in their second and third year of metamorphosis.
So far, a direct control for wireworms in or immediately before susceptible crops has not yet been achieved.
Reduce the infestation risk by planning your crop rotation: By cultivating a one-year grass-clover ley and by placing the potatoes after the third or even fourth year of ploughing the ley, the intensity of infestation can be considerably lowered.
• Perennial grass-clover leys promote wireworms. For this reason, a perennial cultivation of grass-clover ley should be avoided if there is any indication of wireworm infestation.
• After ploughing the meadows or the perennial grass-clover ley, wait until the third or, if possible, even fourth year to plant susceptible crops like potatoes, carrots, onions or salad.
• In general, a diverse crop rotation promotes various beneficial organisms and lowers the infestation of wireworms.
• No cultivation of potatoes in strongly affected areas!
• Rye, fodder radish and vetch are a possible green manure for overwintering. A low infestation of wireworms was observed in crop rotations with peas and lupines.
• The cultivation of legumes (peas, field beans, bush beans) and Brassicas (white cabbage, fodder radish, mustards) can reduce damage from wireworms.
• Grain legumes but also cereals are ideal preceding crops for potatoes.
• Keep the soil moist whilst allowing the potatoes to mature.
• Harvest the potatoes on time because the longer the tubers are in the soil, the more risk of an infestation increases
• Control couch grass (Elymus repens) because its roots can promote the metamorphosis of the wireworm larvae.