MAIN CAUSE OF DEATH OF THE APRICOT TREES IN BULGARIA

Under the influence of favourable market conditions, between the First and Second World War, quite large apricot plantings have been established in this country, mainly in south Bulgaria and particularly in the Marica Valley. Apricot plantings were concentrated chiefly in this part of the country because of considering the apricot tree as a thermophylic plant. But just in these regions, the number of dying apricot trees used to be the largest, relatively much larger than in north Bulgaria.. Apricot tree perishing occurs mainly in spring and usually is called apoplexy. It is characterized by wilting and drying of single branches or whole plants without visible causes.

Apricot hybrid plants and seedlings as products of tree pollination perish also en masse in the selection gardens of the Fruit Growing Reaserch Institute in Plovdiv, and for this reason, a special investigation has been undertaken. Results from this study are briefly reported in this paper.

All 432 trees which died in the apricot selection gardens have been investigated during the period 1960–1963. They were mainly 3–6 years old and made up about 27% of the total number of available trees. Buds of the native Kustendil Blue Plum variety and Reine Claude Verte variety /a smaller number/ have been grafted at stem height on the heads of 188 examined dead trees at two years of age. These graftings have been made with the purpose to play a role of mentors and to induce prolongation of the dormancy period. '/ Heads of such trees consisted both of apricot and plum branches. An insignificant part of the investigated trees did not grow on own roots and stem; they were grafted