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Now that most of the chemical thinning sprays have gone on, we are waiting for fruit drop triggered by the secondary thinners to occur.
Until this drop is complete, trying to hand thin is a futile exercise and may also run the risk of overthinning if it is done too early and appreciable fruit drop occurs after the hand thinning.
Fruitlet drop following Cylex or Carbaryl may take as much as three weeks or longer from time of application to occur. Even so, fruitlets which are going to drop will show up about ten days after application. The first signs that they are going to drop will be allowing up of fruitlet growth rates relative to the unaffected fruitlets. About this stage, healthy fruit also begin to loose their pubescence and take on a glossy appearance while whose which are going to drop have a matt finish rather than glossy green appearance.
While waiting for fruitlets to fall there are many other important jobs which can be done around the orchard.
These include:
- Water shoot plucking.
- Girdling for vigour control and return bloom.
- Weed control around young trees.
- Care of young trees.
Water Shoot Plucking
Water shoots arise from the heavier branches in the tree where major pruning cuts were made. If left, these create heavy shade, rob the fruit of carbohydrates, compete for calcium and add greatly to next year's pruning cost.
At this time of the year, they can be readily pulled out. The job is very quick and because of the whole shoot comes out, regrowth from adventitious buds is avoided. Once the shoots begin to lignify, they become difficult to pull out and need secateurs. Cutting with secateurs leaves that adventitious buds behind to regrow.
Girdling
Ringing and girdling has now become an established practice for vigour control and stimulation of return bloom.
Our trial work has shown that the optimum timing for girdling appears to be late November into early December. Once the secondary thinner fruit drop is underway, it is time to start girdling. Vigour control at this time of the year usually ranges around 30 to 50% of the untreated control.
Biennial varieties, eg, Pacific Rose on vigourous rootstocks such as M793 look as if they need regular girdling to guarantee full return bloom.
For younger trees with trunk diameters up to 75 mm, a simple knife cut or saw cut without removing any bark does a good job and is best done as a tight spiral with overlap of 10 mm and separation at overlap of 5 mm.
Bigger trees generally require bark removed using either 3 mm or 7 mm knives. The standard technique is the Double "C" cut with 50 mm separation and 50 mm overlap.
For any girdling treatment to work, it is necessary to sever the bark completely down to the wood.
Weed Control
November and December sees the germination of the summer weed seed population. Their seeds require heat and moisture for germination and grow very rapidly once they start.
In young orchards there is little shade from the tree canopy, so these summer weeds can be very aggressive. They are most easily controlled when in the small seedling stage.
A word of warning when spraying young trees. Their bark is not as robust as older trees, so it is easily scuffed or burnt by weed control operations. With contact materials such as paraquat or Buster, safety is very much dependant on concentration. Recently we have come across instances of injury where young trees have been sprayed using weed sprays designed to operate at low water volume with high chemical concentration. Also, if herbicide soaked nozzle hoods come in direct contact with the tree trunk and scuff it, injury is likely to occur.
Care of Young Trees
Young trees have a tendency to set excessive fruit on branch terminals and towards the top of the leader. If left on, this fruit bends the branch or leader out of shape and stifles further development.
We have found cutting 20 or 30 cm back into the leader tip or branch end removes the damaging fruit weight and is enough to stiffen the end, so growth will continue without problems. This is very quick and a much better option than trying to thin the fruit.
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