Avocado Algal Leaf Disease: Treating Spots On Avocado Leaves

Avocado Leaf Spotted Brown with Avocado Algal Disease
alal avocado
(Image credit: Holly Thornton, University of Georgia, Bugwood.org)

Gearing up for avocado season means so much more if you’re growing your own alligator pears. Instead of eating the neighbor’s famous guacamole, it’s yours that everyone on the block will be after, but when your avocado tree develops leaf spots, does that mean the party’s over? The answer is that it depends on what’s causing the spot, but if it’s algal leaf spot of avocado, you can still have a healthy and abundant harvest after all!

Algal Leaf Spot of Avocado

Avocado leaf diseases can look so bad that a homeowner will question whether or not their tree will make it to harvest time. Fortunately, many avocado leaf diseases look a lot worse than they really are for established trees, and algal leaf spot of avocados is one of the easy ones! You’ll know you have avocado algal leaf disease when green, yellowish, or red orange raised spots start to appear in abundance on your avocado leaves. Sometimes those spots spread to twigs and branches or come together to create larger blobs of discolored tissue. As the algal reproductive systems mature, the spots will all turn rust-colored and may also discolor the unaffected side of the leaf.

Algal Leaf Spot Treatment

As awful as those algal leaf spots look, they’re not necessarily damaging your tree. If you can bear the appearance and your tree is producing well, you can continue on with business as usual. It might be a good idea to remove any debris or weeds around the trunks of these trees, as well as thinning the interior of the plant to ensure that maximum air flow is available to dry out leaves and bark. After all, avocado algal leaf disease depends heavily on moisture to thrive. If younger trees or vital landscape plants are affected, treating spots on avocado leaves is easy. Even though the existing spots will remain after treatment, you can prevent new spots from forming by thinning the tree and spraying it with a copper fungicide. Trees that have had repeated problems with algal leaf spot and have been thinned may need to be treated on a schedule, just make sure to observe any hold times before harvesting fruit.

Kristi Waterworth

Kristi Waterworth was a regular contributor to Gardening Know How for many years, answering countless queries on plant pests and diseases.