THE EFFECT OF POLLINATOR DENSITY ON THE BEHAVIOUR OF DOYENNE DU COMICE PEAR

The pear cultivar Doyenné du Comice is not a very fruitful one. Full grown Dutch orchards yield 16 to 25 tonnes per ha (with densities of 800–1400 trees per ha) or 19 to 27 tonnes (1400–2000 trees per ha). For comparison, the main cultivar Conference yields 26 to 34 and 27 to 36 tonnes in the same density ranges. The question arises as to whether the productivity of Doyenné du Comice can be increased by augmenting the pollinator density. Doyenné du Comice is classified as self sterile (/10/ /11/ /19/). It does not set parthenocarpically either /12/, although this is disputed /5/. Therefore, a good cross pollination level seems necessary. Indeed, Williams /28/ in England showed that additional hand pollination can increase fruit set, albeit not in all cases. On the other hand too much cross pollination might be detrimental, since seeded fruits may suppress flower-bud formation (/7/ /9/). Heavy yield of seeded fruits could thus induce biennialism and it is known that Doyenné du Comice is rather biennial. In order to obtain more information on the behaviour of Doyenné du Comice under various pollination regimes the present trial was carried out.