Assessment of Alternative Bud Break Enhancers for Commercial Kiwifruit Production of ‘Zesy002’ (Gold3)

Abstract

The kiwifruit (Actinidia chinensis Planch.) cultivar ‘Zesy002’ (Gold3) has shown some inconsistency in its pattern of bud break and flowering when treated with the bud break enhancing agent hydrogen cyanamide (HC), during the first years of this cultivar’s existence. Given the potential for this product to be de-registered for use in the New Zealand kiwifruit industry, as happened in the European Union, there is a need to find alternatives to HC. In this study, the bud break and flowering patterns of ‘Gold3’ were studied when treated with HC or with the alternative bud break enhancers ArmobreakTM (AB) and Erger® (ER) at five different application dates [45, 39, 33, 25 and 17 days before natural bud break (DBNB)]. On each application date, the treatment products were paint brush applied to individual canes with all products represented on each individual vine. Bud break and flowering progression were then monitored for all treatments. The 2012 winter chill for the area was 445 h below 7 ℃, compared to the 18 year average of 394 h. This investigation on the ‘Gold3’ cultivar indicated that AB and ER maybe potential alternatives to HC but they induced significantly lower flower loadings than HC. HC also has a wider time window for successful application, from 45 down to 33 DBNB; there may be potential for even earlier successful application of HC but such dates were not investigated in this work. Based on this study, the best application timings for the alternative bud break enhancers to HC for ‘Gold3’ was from 33 to 25 DBNB.