The leaves on my avocado tree developed brown spots. I've heard it's because I did not plant a second avocado tree near it. Is that true? —Brandy Schmidt, Carmichael, California
The brown spots could be attributed to one of several diseases, including leaf spot, anthracnose or scab, but not the lack of a second tree. This relates only to pollination and fruit production. Although most avocados are self-fruitful (only need one tree to produce fruit), they have greater production when a second tree is added for cross-pollination.
To help keep the disease from spreading, rake and destroy the leaves as they drop from the tree. This will help prevent future infection.
Also, avoid overhead and nighttime watering because these create the perfect environment for disease. If the problem continues, consult your local extension service for a definitive diagnosis and recommended control.
If you decide to add a second tree, water young plantings thoroughly and whenever the top few inches of soil are crumbly and moist. Pay special attention the first 2 to 3 years as the tree becomes established. Mulching the soil around the tree will help keep the soil cool and moist.