How to Get Rid of Root Rot in an Avocado Tree

Examine your avocado trees for telltale signs of root rot. Look for small leaves with a yellow or greenish hue. Notice if the leaves wilt, and have necrotic or dead tips. Smaller branches will die, exposing the fruit to too much sunlight, which can cause sunburned fruit. The avocado fruit will also be much smaller than normal, and there will be many dead leaves on the ground surrounding the tree.

Apply a heavy layer of gypsum on the ground directly beneath the tree's canopy. Use up to 25 pounds of gypsum for each avocado tree. Gypsum supplies calcium to the soil, and it will suppress the formation of the root rot spores.

Spread a layer of mulch around the tree. Use a shovel to apply a 4- to 6-inch layer of mulch on top of the gypsum. Use yard waste such as grass clippings or hardwood chips. Keep the mulch three to four inches away from the trunk of the tree. The mulch encourages growth of microorganisms that fight and slow down the spread of root rot.

Apply a phosphonate fungicide to the infected tree. Phosphonate fungicides should be injected into the tree trunk, sprayed onto the bark or applied to the soil around the tree. Apply the fungicide according to the product directions. The fungicide will help kill the root rot fungus, but it should be used in conjunction with other forms of treatment such as gypsum and mulching for maximum effect.

Rotate your plants. Avoid growing avocados in the same soil two seasons in a row if you experience an outbreak of root rot. Grow plants that are resistant to root rot, such as citrus and persimmon. The fungus will eventually die in the soil without a suitable host, which will allow you to plant avocados again in the future.