What Causes Wilted Foliage on Avocado Trees?

Verticillium Wilt

• Verticillium wilt caused by the pathogen Verticillium dahliae frequently infects avocado trees, destroying entire branches of leaves as they turn brown, wilt and die, with the dead leaves likely to remain on the tree for several months. New shoots often develop to replace the lost foliage, but the disease usually returns to attack the tree. The fungus remains in infected soil for years and affects the root system of the tree, disabling roots from providing water and nutrition to the leaves.

Avocado Lace Bug

• The avocado lace bug (Pseudacysta perseae) also is referred to as the camphor lace bug. This pest ignores the fruit of the tree and feeds on avocado leaves, sucking away sap and leaving brown or tan spots on the foliage. As the feeding continues, these blotches worsen and the entire leaf dries, curls, wilts and prematurely falls. An additional sign of the bugs' presence are tiny black spots -- the insects' waste -- that appear on the upper surface of the leaves.

Phytophthora Root Rot

• Phytophthora root rot is the most damaging and prevalent disease avocado trees face. The pathogen first displays in the foliage of the tree, causing the leaves to grow smaller, discolor and wilt. The avocado leaves prematurely fall to the ground and entire branches are defoliated. As the roots of the tree rot away, the avocado specimen may die quickly over the course of several months, or decline gradually over the span of several years. Fruit quality is drastically diminished.

Laurel Wilt

• The fungal disease laurel wilt is introduced to the avocado tree via an insect, the redbay ambrosia beetle (Xyleborus glabratus). The tiny dark-brown or black beetle, loaded with fungal spores, bores into the wood of the tree, infecting it with the disease. As the fungus grows, the beetle feeds on the fungus. Meanwhile, the fungus spreads throughout the tree, blocking the ability of water and nutrition to properly circulate. As a result, the leaves of the avocado begin to wilt and die.