Articles
FRUIT SET AND GROWTH REACTIONS OF PEAR TREES, CV. DOYENNE DU COMICE ON QUINCE A, PRUNED AT DIFFERENT RATIOS OF VEGETATIVE ON GENERATIVE BUDS
The number of buds are expressed per metre frame-wood (>2 cm thickness). The following V/G ratios were chosen : 75/15, 90/30, 135/30, 75/45 and 135/45 for group A, B, C, D and E respectively.
The mean annual yields were highest whereas mean fruit weight and mean growth rate were lowest on the most weakly pruned object E. The expected number of flower clusters as a result of the treatments was reached every year on all objects, except on the D object, after a heavy crop.
This indicates a higher sensitivity of the D trees for biennial bearing.
The increase of the tree volume (metres of frame-wood and canopy diametre) was lowest on the heavily pruned objects A and D, and higher on the weakly pruned E object.
Fruit retention was clearly highest on the A object, which had the lowest number of flower clusters.
The significance of strong growth reactions (one year shoots) and the competitive role of the retained two year old twigs in relation with fruit production seems rather complex.
The large amount of one year old shoots on the severely pruned A and B object probably contributed to lowering the yields.
On the D object, the fairly strong growth of the shoots and the scarce presence of two year old twigs corresponded with fairly low fruit retention and rather low mean fruit weights.
This was compensated for by the presence of a high number of fruits, as a result of the many flower clusters.
A financial analysis led to the conclusion that the pruning of adult Doyenné trees in order to maximize yields in relatively dense orchards should be different from pruning in orchards with larger spacing.
In the latter case, a V/G ratio of 135/30 was optimum.
In a denser orchard, the V/G ratio of 70/45 would rather be the optimum, i.e. that in these conditions one has to intend to get 45 blossom clusters per metre frame-wood every year and to maintain only a minimum of one year shoots (leaf buds). As this status could not be reached every year, leaving more than 45 flower clusters per metre frame-wood seems to present a risk for biennial bearing.