Causal agent(s) and transmission
Common or March craneflies (Tipula paludosa and T. oleracea) belong to the order Diptera. Adults, which are non-damaging, are flies with a thin body about 16-25 mm long, transparent and ribbed wings and very long fragile legs (photo 1). The larval stages of craneflies are known as leatherjackets (photo 2) and are grey legless larvae (maggots) with biting mouthparts and a tough rubbery skin, with a body measuring 3 to 4 cm, which can extend and retract easily.
The larvae of craneflies feed on roots, sprouts and underground or emerging organs of many plants and can thus cause damage to the potato by reducing the root system or by gnawing the tubers. Foci of soil infestation can display poor plant vigor and even failure on emergence, caused by the larvae feeding on and cutting the underground stems and roots.
Cranefly damage can usually be observed in spring when leatherjackets are most active and when many are present due to favourable conditions: a mild winter, a cool, humid spring, permanent meadows or fallow land. Conversely, harsh winters or soil cultivation can substantially reduce cranefly populations