Leaf defoliation in low-chilling environments

March 2017 | Susie Murphy White | Future Orchards® trial report, South West Western Australia

This Future Orchards® trial asked whether deliberate leaf defoliation could help apple trees enter dormancy earlier and therefore accumulate more effective winter chill in a low-chill environment. The work was conducted in South West Western Australia with Susie Murphy White as the project contact.

The demonstration compared four treatments — urea, hydrogen cyanamide, ABA and an untreated control — using a randomised design on Cripps Pink apples. Applications were made in late May, with winter chill monitored in the orchard and weekly photographs taken to track leaf fall.

Follow-up assessments included the timing of 5% green tip and 80% full bloom. The project was designed to connect leaf-removal timing with later dormancy and flowering behaviour, giving growers a practical way to evaluate whether autumn defoliation can improve the use of limited winter chill.

The trial is particularly relevant to warm apple-growing districts where trees can retain leaves late into autumn and where insufficient chilling can lead to delayed or uneven budbreak in spring.