An attempt in progress to eradicate plum pox

Plum pox (PP) or sharka disease was introduced more than ten years ago into the Sarca Valley (Trento province), an area where the well known Dro Plum cultivar has been cultivated for a long time. The old plum variety is quite sensitive to PP and yield of the trees is negatively influenced, too. A systematic survey carried out during 1984 and 1985 in the Sarca Valley, with the purpose of setting up a plan of eradication, established that 34 442 trees out of the 261 772 checked (about 13%) were showing PP symptoms. After transferring the data acquired onto a map of the Valley, using different colours for each class of incidence, it was possible to distinguish 11 plum zones isolated by natural barriers having different incidences of the disease. On such a basis a work plan distinguishing three criteria of intervention was started in 1985/86. In the zones with a rather modest incidence of the disease, extirpation of the symptom showing trees and of part of the symptomless ones was carried out each year by the growers, and a reduction in the percentage of affected trees was noticed in the systematic check carried out in 1986 and 1987. In the two zones with an average incidence of PP above 20%, it was impossible to extirpate all the stonefruit trees susceptible to sharka as would be necessary for the replanting of Dro Plum, and consequently the eradication program was suspended. An isolation band specifically created would prevent spreading of sharka in the contiguous plum areas. Although up to now results have been only partial, the plan of intervention is continuing in the seven zones with an average incidence of the disease below 5% and in the two zones where it is now around 7%. It is hoped that at least in the former zones the disease can be eradicated, if the growers accurately follow the suggestions supplied