Spring is here and so is chemical thinning

Posted By HBFA | October 24, 2023

Most of the trees have now woken up, with primary thinning decisions waiting to be executed when the weather window presents itself.

You will have heard this repeated across a few forums now, but this season more than ever, boots on the ground in the orchard, will be critical to confirm chemical thinning decision making.  Chemical thinning always requires a careful assessment and knowledge of each block, but coming off the back of the 2023 season where we know tree health has been compromised, walking the orchard has more meaning than ever before.

The ground was waterlogged for significant periods right across the bay, with some orchards having the added complication of silt deposition of varying depths across the blocks.  Reduced solar radiation over the 2023 season means that the tree’s carbohydrate reserves may be lower, and in some orchards a lack of pruning may mean higher bud loads than normal.  Consequently, tree health will be a significant factor when making crop loading and therefore chemical thinning decisions. Things to look out for include variations of bloom density and synchronisation, flower development and leaf quality all provide a picture of potential tree stress.

Check your drainage and soil moisture levels before launching into an aggressive chemical thinning programme. Especially in situations with dark/shaded canopies, poor nutrient status and wet feet.  Chemical thinning brews need to be carefully considered, as most products add an additional stressor to an already stressed trees.

In areas where trees have poor root health, and low carbohydrate reserves, there may be a high natural drop. In blocks which have been severely affected, leaving the crops to set naturally and observe at the 6-7mm may be a more cautious strategy.

At a time when the labour cost is significant, we want to achieve full crops on the higher margin varieties, and reduce the hand thinning costs on others.

Once you have formed your plan, you can alter it as the weather windows and natural flower stages and fruit set allow.

Sarah de Bruin

Agfirst Horticultural Consultant


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