The plant ailment, known as "Fusarium dieback," was identified recently by UC Riverside extension plant pathologist Akif Eskalen.
California is already battling the Asian citrus psyllid, which spreads a disease that is threatening the state's $2-billion citrus industry. Recently they have got a new problem: the tea shot hole borer is an ambrosia beetle about the size of a sesame seed. It carries the Fusarium fungus in its mouth. When the beetle burrows into an avocado tree, it infects the plant with the fungus. Fusarium then attacks the tree's vascular tissue, interrupting the flow of water and nutrients.
Telltale signs of an infestation include dead or dying branches, as well as beetle exit holes on the bark of the tree's trunk or main branches. The wood near these exit holes may be discolored, wet-looking or be coated with a white, powdery substance.