Potato Virus Y reduction by straw mulch in organic potatoes

Abstract

Potato virus Y (PVY) is transmitted non-persistently by winged morphs of many aphid species and is a major problem in seed potato production. In order to evaluate the potential of straw mulch applications (4-5 t ha-1) and presprouting on PVY reduction, small scale organically managed field experiments were carried out in Northern Hessen, Germany, over 3 yr. In all years mulching significantly reduced aphid infestation on leaves as well as PVY incidence in tubers. For the effect of presprouting the temporal coincidence of two factors was crucial � crop emergence and aphid flight activity. Presprouting decreased PVY incidence when in the phase of early crop emergence aphid spring flight activity was low, but increased it, although not significantly, when prominent aphid flight peaks occurred in this critical period. Straw mulch was most effective when vector pressure was concentrated early in the year acting as a PVY protectant for young plants. In later growth stages its effect declined gradually with increasing ground coverage of the crop. Combined mulching and presprouting had a synergistic, complementary effect on reduction of PVY incidence. In an on-farm experiment in 2001 scaling up the area mulched stepwise from 100 m² to 900 m² consistently kept aphid infestation at reduced levels