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Cyclone recovery for avocado, macadamia, lychee and custard apple trees

There are many things you can do to manage cyclone-affected tree crops. Below is advice on specific tree types (avocado, macadamia, lychee, custard apple), including information on restoring damaged trees, taking remedial measures to minimise future loss, and managing fruit.

Avocado trees

Immediate treatment

Fruit on the tree may have been affected by wind damage. Fruit may be bruised, and some may have cuts and chunks out of them. A copper spray at this stage will help protect the fruit from both bacterial and fungal breakdown that will be aggravated by this damage. It will also protect damaged leaves and branches. Choose a product that leaves minimal residue, such as red copper. Alternatively, you can apply an azoxystrobin fungicide (within the label's resistance management guidelines), against anthracnose after the cyclone, as a curative and preventive fungicide.

Bruising and fruit damage will be clearly visible after a few days, and pickers should avoid harvesting damaged fruit. Treat fruit with normal post-harvest treatments, making sure that equipment is cleaned carefully if any fruit with bacterial soft rot goes through the packing line.

Some trees that have blown over can be salvaged if root damage is not too extensive. Prune and prop the trees to help them recover. When propping, lift the trees while the soil is still wet, being careful not to damage the remaining roots. Stop lifting the tree if you hear cracking due to the root snapping on the downwind side. If in doubt, leave the tree as it fell and prune to a new shape over several years. Prune off the canopy proportionally to the amount of root loss/damage. Treat limbs for sunburn with a 1:4:20 mix of water-based white acrylic paint, micro fine lime and water (i.e. 1L paint, 4kg lime and 20L water). Treat the ground with a fungicide (e.g. phosphoric acid or Ridomil) for phytophthora.

Consider sunburn protection for fruit remaining on trees, as fruit will be more exposed when leaves have been stripped from the tree. This is particularly the case with Hass. A spray-on crop protectant is recommended. You will need to gauge the volume for each tree, as this will depend on the amount of canopy lost. Apply enough protectant to get good coverage, but not to the point of run-off.

Longer-term phytophthora control treatment

Normally a phosphorous acid injection is recommended for March, and this injection is more important than ever following heavy rain during a cyclone. Injections are favoured over foliar sprays because the leaf area needed to absorb the phosphorous acid has been reduced by the cyclone, to the point where there is not enough leaf area for sufficient absorption.

Macadamia trees

Macadamias are particularly brittle and prone to cyclone damage. Consider strategies for clearing tree rows, salvaging trees where possible and recover fallen nuts from areas where you can gain machinery access.

You should prune trees to take out any damaged and broken or twisted limbs, and apply a 1:4:20 mix of water-based white acrylic paint, micro fine lime and water to protect exposed limbs against sunburn. Pruning trees to a central main leader can provide more resilience to future high-wind events.

Lychee trees

Many trees break or twist off at ground level, and you will need to replant these. Where trees have not broken, prop and prune to reduce the canopy to help trees recover. Open out the centre of the tree by removing selected internal branches.

Custard apples

The first step to recovery is to stand trees back up as soon as possible and while the soil is still wet. When this is done, broken branches are pruned and debris is cleared, spray all trees with a preventative fungicide such as mancozeb or copper.

If the canopy has been significantly reduced, apply 1:4:20 mix of water-based white acrylic paint, micro fine lime and water to protect exposed limbs against sunburn.

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