Abstract
Fruit thinning is an important management practice in commercial apple production. The standard industry practice for crop load management in many countries is based on bloom and/or post-bloom chemical thinning (CT) followed up with hand thinning. However, the response to CT is unpredictable and there is an increasing awareness of the environmental impact of many chemicals. Hence there is a need to find alternate environmentally acceptable methods for managing crop load. Artificial bud extinction (ABE), a thinning method that imitates natural bud extinction by manually removing buds before bud break, has been suggested as a potential tool to replace chemical thinning, but there have been no studies comparing ABE and chemical thinning. Trials were established in Tasmania, Australia to determine how ABE technology compares with best practice CT programs in terms of yield, fruit quality, and cost of implementation. Results from these trials demonstrated consistent fruit set of both Gala and Fuji apple under ABE management compared with conventional management. Fruit weight was increased in all ABE treatments from 5% up to 38%. The four studies presented here have demonstrated that ABE is a feasible alternative to chemical thinning, improving reliability of crop load management with increased predictability of fruit size and yield. Trees are significantly thinned before flowering, controlling biennial bearing. In addition, bud position is optimised, fruit is well spaced and light distribution into the canopy is enhanced. In terms of costs, implementation of ABE is comparable to managing crop load with CT programs but has the advantage that crop load management costs reduce in subsequent years after the initial tree set-up. ABE is also suitable for use in organic apple orchards.
Highlights
Crop load management is undertaken in modern apple (Malus x domestica Borkh.) production to ensure regular bearing and good fruit quality, and according to Looney [1], fruit thinning is considered one of the most important orchard management practices
The four studies presented here have demonstrated that Artificial bud extinction (ABE) is a feasible alternative to chemical thinning, improving reliability of crop load management with increased predictability of fruit size and yield
The four studies presented here have demonstrated that ABE is a feasible alternative to chemical thinning for crop load management in apple, validating the suggestion by Tustin et al [11] that ABE
Summary
Crop load management is undertaken in modern apple (Malus x domestica Borkh.) production to ensure regular bearing and good fruit quality, and according to Looney [1], fruit thinning is considered one of the most important orchard management practices. The response to chemical thinning is very weather-dependent and there is considerable variation between cultivars in sensitivity to thinning chemicals [3] This lack of predictability, combined with an increasing awareness of the environmental impact of many chemicals and the loss of registration of some chemicals, points to a need to find alternate environmentally acceptable methods for managing crop load [4]. Thinning method had no effect on blush intensity or fruit shape (Table 6), or on DMC, firmness or malic acid content (Table 7). Both mean fruit weight and Fruit TSS were lower in the late hand-thinned treatments compared with the early hand-thinned and chemical thinned treatments (Table 7).
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