Coping with Defoliated Avocado Trees
Sometimes, a combination of weather factors — or extensive pruning — can lead to defoliated trees. As Dr. Ben Faber discusses in his “Heat, Wind, Freeze, Wind, Repeat” blog post, this can be problematic as the tree then has no way of moving water because the leaves aren’t present to transpire and create water flow. A lack of leaves can quickly lead to sunburned fruit or limbs on warm days (about 80 degrees or warmer). If the sunburn is intense, it can kill the green cambium below the bark and either kill a young tree or cause significant damage to an older one.
Although trees can recover from sunburn, Dr. Faber recommends preventing the sunburn in the first place by whitewashing the tops of branches and the portions of the trunk that face south and west. Interior white latex paint will suffice, but you also can make your own whitewash by combining 0.4 pounds of zinc sulfate with 5 pounds of hydrated lime and mixing with 10 gallons of water. If you choose to use latex paint, dilute it to a 1:1 ratio of water to paint.
If you conduct extensive pruning that leaves portions of the trunk and major limbs exposed, it’s best to apply whitewash immediately on the day of pruning. You also can whitewash the tree prior to pruning in order to avoid coating the pruning wound, which tends to inhibit a tree’s normal wound healing process.
If recent weather conditions or pruning aren’t the cause of defoliation, be certain to determine whether the tree is suffering from root rot, crown rot or poor irrigation. And remember that a defoliated tree uses less water, so avoid irrigating until the root zone begins to dry.