Laurel Wilt Experts Caution California Avocado Industry

Taylor HillmanFruits & Vegetables, Pest Update

The California avocado industry probed Florida laurel wilt disease experts at the final installment of the 2017 Avocado Growers Seminar Series, sponsored by the California Avocado Commission, U.C. Cooperative Extension, and the California Avocado Society.

Laurel Wilt Seminar

Florida laurel wilt experts present research to San Luis Obispo growers.

A group of six University of Florida (UF) researchers discussed laurel wilt disease at three seminars in avocado producing areas of California. Laurel wilt is a vascular disease caused by a fungus that affects trees in the Laurel family. The disease isn’t in California yet, but it’s spreading west from the deep southeast across the Southern United States.

The fungus is introduced by ambrosia beetles, primarily the redbay beetle, but the disease can also be transmitted through integrated root systems. UF Tropical Fruit Crop Advisor Jonathon Crane showed attendees how quickly the disease could kill avocado trees with a series of slides. “What that was trying to demonstrate is that this disease moves so fast through the root grafts amongst adjacent trees that if you do not implement sanitation procedures as quickly as possible, in addition to identifying very early symptimatic trees as quickly as possible, it will move before you know it,” Crane warned.

Laurel Wilt Seminar Slide

Slide showing other beetles can also spread the fungus

Florida has lost 40,000 acres of avocado trees to the disease. Laurel Wilt was detected in the U.S. in 2002 and found in Florida in 2005. Crane said once clear visual signs of the disease are apparent, it is often too late. “Once you see the green leaves wilting, it’s already wreaked quite a bit of havoc inside the tree,” Crane said. “Once it turns brown, it’s not only wreaked havoc inside that tree, but it’s probably moved to its neighbor through the root system.”

The sanitation practices Crane talks about involve scouting, rouging and spot treating. Florida researchers agree that the best way to manage the disease is to identify infected trees as early as possible, remove and destroy those infected trees and treat the surrounding trees with insecticides.

Laurel wilt has been found as far west as Texas. Crane said the disease could spread quickly through California if it gets here because of the variety of trees in the state. “The California Bay laurel, like our native trees, emit an aroma that attracts beetles and this redbay ambrosia beetle especially,” Crane said. “People have done work to show that the redbay ambrosia beetle will attack the California Bay and the fungus will kill it.”

Listen to Crane’s full interview.
08-02 Jonathon Crane UF