All About Avocados
I have avocado leaves that look like they have tiny burn marks on them. What’s causing this? This is the most frequent question I have been asked in the last six months. The leaf damage is being caused by the avocado lace bug. If you turn the leaf over and look on the back you should be able to see very small, black insects that are feeding on the leaf and causing the damage. The good news is that avocado leaves drop right before the tree blooms, so the damaged leaves will soon be gone and replaced by clean, healthy leaves.
My avocado tree rapidly turned brown and died. What happened to my tree? In very few cases, this can be caused by a lightning strike. But since the arrival of the disease laurel wilt in 2012, rapid death and wilting of avocado trees is becoming more and more prevalent. The disease is spread by a tiny ambrosia beetle that drills into the tree to grow the deadly fungus, Raffaelea lauricola, to feed its young. The tree overreacts to the fungus by trying to wall it off. It ends up blocking its own vascular system, which results in rapid wilt and death. The disease can also be spread through root grafting if avocado trees are close enough.
If I want to plant an avocado, are there any resistant cultivars to look for? There are no resistant cultivars. The University of Florida is testing different rootstocks that are being used heavily in California, but that work still has a long way to go to see if something will be resistant. A small bit of good news is that young trees are far less likely to be attacked by the ambrosia beetles that carry the disease. The beetles prefer avocado trees with wider trunks and ones that provide more shade.
If my neighbor’s tree has laurel wilt, will it spread to mine? Remember, there are two primary ways the disease can travel: through beetle activity and through root grafts. If a neighbor’s tree has laurel wilt, that probably means that there are a large number of beetles in the tree. Those beetles could attack your tree. If your tree and your neighbor’s tree are growing near each other and the trees are old enough to have a large root system, the trees may be root grafted and your tree is in danger of getting laurel wilt.
What do I do with my tree if it does have laurel wilt? A large dead tree is a safety hazard and it harbors beetles. Quickly remove and destroy the tree. Chip it in place for mulch, or take it to the nearest Miami-Dade waste disposal site. These sites are free for county residents to dump. If the tree is near other avocado trees, try to break the root system so root-to-root transmission is not possible.
Questions about your tropical fruit trees? Call a UF/IFAS extension agent at 305-248-3311.
Homeowners: Adrian Hunsberger (ext. 236)
Commercial tropical fruit growers: Jeff Wasielewski (ext. 227)
Commercial vegetable growers: Qingren Wang (ext. 234)
