Strategies to control tree vigour and optimise fruit production in 'Conference' pears

The ban on the use of chlormequat (CCC) in pear orchards in 2001 forced Dutch pear growers to look for alternative methods to control tree vigour and stimulate flower bud development and fruit production. Root pruning and trunk notching have become the major growth retarding methods. In addition to the mechanical methods for controlling tree vigour, Regalis (Prohexadione-Calcium) and ethephon were tested as alternative chemical growth regulators for 'Conference' pears. In 2004, a trial was started in which six different strategies to control tree vigour and optimize fruit production in 'Conference' trees are compared. In 4 strategies root pruning was the major treatment, while in 2 strategies trunk incisions were the initial treatment to reduce tree vigour and stimulate fruit production. In 2005, no further root pruning or trunk incisions were made and ethephon and Regalis were the only treatments applied in some of the strategies. Ethephon and Regalis were also applied in 2006 in addition to root pruning in March and June or in June only. All of the strategies evaluated significantly reduced shoot growth and improved fruit production. Regular yields of 52 to more than 70 tons/ha were achieved for 3 consecutive years. So far, ethephon and Regalis have shown no or only minor additional beneficial effects compared to root pruning or trunk incision followed by root pruning in the years thereafter. Flowering, fruit yield and fruit quality of 'Conference' pears produced using the different strategies are presented and discussed