Flower (blossom) thinning
If current guidelines on rates and timings are observed, over thinning with a chemical blossom thinner is unlikely. The aim is to reduce the cost of hand thinning.
Before deciding on blossom thinning it is important to ask:
- Does historical data show consistently that thinning is necessary?
- Are the flower cluster numbers twice as high (or more) than necessary for a good set?
- Has there been little or no frost damage and none forecast?
If the answer is yes to the above it is definitely appropriate to consider blossom thinning.
Fruitlet thinning
When contemplating the need for thinning of fruitlets it is vital to ask:
- Are trees compact in growth?
- Are leaves small and dark?
- Are fruitlet numbers double or more than required?
- Are fruitlets clearly visible above foliage?
If the answer is yes to the above it is definitely appropriate to consider a fruitlet thinning treatment.
Hand thinning
When contemplating the need for hand thinning of fruitlets, it is vital to follow the following guidelines:
- Check fruit numbers on at least 10 representative trees in each orchard.
- Estimate whether fruit numbers more than 120% of those required at harvest?
- If thinning is warranted, hand thin to optimum fruitlet numbers (before fruitlets reach 25 mm in diameter).
- Remove small and shaded fruitlets and those on weak wood.
- Where fruitlet numbers are between 100% and 120% of optimum, wait and reassess 2‑3 weeks later. If necessary, thin at this later stage removing poor quality fruit.