- Author: Ben Faber
And what do you get, a defoliated tree.
And a defolated tree has no way of moving water through its system. The leaves are not there to transpire and create a flow of water through the tree. When hot day comes – and it does not need to be much hotter than 80 deg – the bark will heat up and “burn”. The bark dries out and the green cambium below dies. If the burn is extensive enough it can easily kill a young tree and can do extensive damage to older trees. It wont be the heat, cold, wind that kills the tree, it's the afterburn.
This damage can heal over, if the problem is fixed soon after the damage has happened. Here's an example of trunk damage that occurred on the south side of the tree that has healed over…. With time.
So what do you do? If trees defoliate, do not irrigate until soil in the root zone approaches dryness. Defoliation reduces tree use of water, so soil will remain wet longer than with unaffected trees. Examine soil carefully and frequently and modify irrigation to prevent excess moisture in the root zone.
And whitewash! Hit the tops of branches and south and west facing parts of the trunk. In general, a whitewash consists of a 1 to 1 ratio of water to interior white latex paint. This diluted mixture allows you to easily spray or paint the wash onto the tree trunk and major limbs. It is critical that the paint is not diluted too much -- you want a strong white color on the avocado tree to reflect sunlight and prevent damage. Alternatively, add 0.4 pounds of zinc sulfate to 5 pounds of hydrated lime and mix with 10 gallons of water. This mixture produces a whitewash that is safe for trees, if you do not have white latex paint available. It is a mess to make, though.
Whitewash the trunk and major limbs of older trees if they develop sparse canopies or are severely pruned, such as when cut back to trunks and grafted with new scion (stumped). Whitewash should also be applied the day of pruning — it takes only a very brief exposure to full, mid-day sun for previously shaded branches to burn. Some growers prefer to whitewash their trees prior to pruning. They do this to prevent the whitewash from coating the pruning wound and inhibiting the normal wound healing response of the tree. If using this approach, be sure that all exposed branches are protected after the pruning is complete, and apply additional whitewash if needed.
And figure out why the canopy is thin if it is not wind heat cold. Is it irrigation? Root Rot? Crown Rot?
Anytime the canopy thins, the fruit is prone to sunburn and you don't make money with that.