Une virose grave du prunier en Yougoslavie

Summary

• 1. The propagation of the plum in Jugoslavia and the spread of the virus disease plum pox is done by the use of suckers. The role ofAnuraphis padi as the vector of plum pox virus is of very little importance, especially in some districts of Serbia.

• 2. The symptoms of plum pox are not always the same. The losses of the crop varies from one year to another and also the number of fruits which have morphological, chemical and physiological changes is not the same always. In some years the number of diseased fruits is smaller and then the crop is almost normal; the causes of these variations are of climatic origin; they very probably depend upon temperature but precise data on this subject must be collected.

• 3. Sometimes the symptoms of plum pox can be masked completely. A tree which is diseased this year can be symptomless the next year.

• 4. In many cases the symptoms of plum pox remain localised in some part of the crown for a long time. Very often they appear only on a few branches. On the other hand, the same branch can show clear symptoms in one year and none in the next. Sometimes the suckers of the stem show symptoms but other parts of the tree show none.

These observations are made on the most sensitive variety ‘Pozegaca’ in the State of serbia and Macedonia.

Some of the causes of irregularity in the activity and behavior of plum pox virus are difficult to explain.