Effects of alternatives to hydrogen cyanamide on commercial 'Hayward' kiwifruit production

The restriction of hydrogen cyanamide (HC) for dormancy interruption of kiwifruit in the European Union leads to a concern among many New Zealand growers about how long the product will be available in their market. A completely randomized block experiment in Auckland region compares the performance of two available alternative dormancy breaking treatments of 'Hayward' green kiwifruit (Actinida deliciosa var. deliciosa 'Hayward'); Erger^® (ER) and Armobreak^® (AB) with HiCane^® (HC) and with an untreated control. Bud break and flowering was studied during three years of different winter chill, ranging from 622 h below 7°C of the 2009 winter to only 301 of the 2011 winter. 'Hayward' kiwifruit shows large sensitivity to winter chill variations. The alternatives to HC improved the percentage of budbreak (%BB) and achieved more inflorescences per winter bud (KFl WB^-1) after high winter chilling. After medium and mild winter chilling, even though the response compared with the control was always improved, the alternatives of HC were less effective than HC.