Summer pruning of apricot Cvs. 'Bora^®' and 'Carmen Top^®'

In the cultivation of apricot, typically characterized by a high vigor, vegetative growth can be controlled by using appropriate rootstocks and pruning techniques. Trimming of apricot shoots is an interesting approach to avoid having the productive area shift to the canopy periphery. This trial was carried out in Imola (Bologna, Italy) on trees planted in 2006 of the 'Carmen Top^®' and 'Bora^®' scion cultivars grafted on Myrobalan 29C rootstock. Trees were trained as V system with a planting density of 1,667 trees/ha. Aims of this study were to verify apricot responses to summer pruning and determine the best time for it, in order to optimize flower buds formation and improve fruit yield. For six weeks starting from June 2008, three blocks of five trees each were pruned to determine the most suitable time for summer pruning. After pruning, the number of new shoots produced by the cuts stimulation and their growth during the season has been evaluated. The number of flowers/tree and number of fruits before and after fruit thinning, together with the yield per tree, were determined in the year subsequent to pruning. The early pruning intervention increased the number of flowers per tree from 2,212 (June 6th) to 2,524 (June 20^th) compared to the un-pruned control that exhibited only 1,938 flowers. An increase in flower numbers is positive in case of frost damage, but improper thinning of too many fruits can negatively affect fruit size. Pruning in early July (4^th) induced a 0.8 kg/tree increase of yield compared with the unpruned control. Despite the same number of flowers/tree, fruit mass of the early July pruning was 10 g less than in fruits of the unpruned control trees.