Thinning For a Drought

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Thinning For a Drought

Apples
Thoroughly and aggressively apply blossom and post-flowering thinning sprays to reduce competition between fruit as soon as possible even though there is a frost risk. This is especially needed if flowering and weather conditions are conducive to high fruit set.

Decide if more thinning is needed at 6 weeks after fruit set and complete the thinning as soon as possible. Secateur thinning can be done in the top third of the tree (vase shaped trees) to speed up thinning until late October.

Choices
Choose to irrigate at a deficit and suffer a fruit size loss. Applying a mild RDI early in the season (mid November and December and again 2 weeks before harvest) will reduce fruit size. In this case heavier and earlier thinning than normal plus RDI will result in lighter crops but similar fruit size compared to a full irrigation program.

Choose not to irrigate. Lower productivity blocks could be de-blossomed or even pollarded (main limbs cut in half or pruned even lower) to reduce water needs. Wound dressing must be applied to these larger pruning cuts. Alternatively, some older trees may be close to being non-viable. This may be a good time to pull them out earlier than planned and transfer the water to productive blocks of trees to ensure some commercially viable fruit can be harvested.

Stone fruit

The stone fruit trees that orchardists have decided to take through to harvest this season need a strong commitment to a thinning program in order to produce saleable, commercial sized fruit when picked.

Last season in all irrigated fruit growing districts, orchardists experienced some problems with fruit size.

In most cases the problem stemmed from what seemed like an average crop early in the season, suffered size losses in last seasons extremely difficult dry season with limited irrigation water allocation.

This problem still looms as a possibility this season, given the early indicators of low water allocations so far and low expectations for rainfall.

Stone fruit trees in the Murray and Goulburn Valleys experienced different stress levels during the growing season last year and will need careful assessment of how much thinning is required this season.

This applies to both canning and market fruit.

The stone fruit trees that orchardists have decided to take through to harvest this season need a strong commitment to a thinning program in order to produce saleable, commercial sized fruit when picked.

Last season in all irrigated fruit growing districts, orchardists experienced some problems with fruit size.

In most cases the problem stemmed from what seemed like an average crop early in the season, suffered size losses in last seasons extremely difficult dry season with limited irrigation water allocation.

This problem still looms as a possibility this season, given the early indicators of low water allocations so far and low expectations for rainfall.

Stone fruit trees in the Murray and Goulburn Valleys experienced different stress levels during the growing season last year and will need careful assessment of how much thinning is required this season.

This applies to both canning and market fruit.

The ‘Golden Rules’ for thinning stone fruit trees are -

Thin early
Thin the earliest maturing varieties first.
Do it right the first time and thin hard enough and focus on what is left on the tree, not what is on the ground.
Supervise the job

Trees with good budwood development last season can easily over-crop, as fruit set during the warm and dry conditions so far are likely to be high. However, trees with poorer budwood can also set a heavy crop but will have lower stored nutrients in the tree from last season; therefore these trees will need accurate assessment and probably thinned more heavily than normal to ensure fruit achieves commercial size and quality.

Secateur thinning by cutting abundantly set laterals in half, is also possible for a quick initial thinning if done by mid October. Hand thinning may then still be needed to space fruit evenly along the remaining lateral.

The risks associated with early thinning are that split stones in fruit may increase and it makes larger fruit more susceptible to cracking close to harvest. However, delayed thinning may result in smaller fruit, especially for early maturing varieties.
Another risk of early thinning is the crop can be lost due to frost damage after being thinned. This results in loss of fruit for packing as well as having spent money on the labour intensive job of thinning.

It seems sensible to use fruit thinning as an offset insurance to obtaining large to average fruit size in a difficult season compared to an average to poor fruit size. This is in a market where fruit size, despite the season, is a key driver of profitable returns.

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