UF Scientists to Help California, Florida Growers Control Dangerous Avocado Pathogen

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Jonathan Crane, professor of horticultural sciences, inspecting an avocado tree at the Tropical Research and Education Center.

By Brad Buck, 352-294-3303, bradbuck@ufl.edu

GAINESVILLE, Fla. — University of Florida experts know all too well about laurel wilt, the pathogen endangering the state’s $100 million-a-year avocado industry – and they’re trying to find ways to prevent it from spreading. Now, they’re taking their data to California to talk to scientists, growers and regulators.

Faculty from the University of Florida/Institute of Food and Agricultural Sciences (UF/IFAS) Tropical Research and Education Center are in California this week to speak at a series of seminars on laurel wilt, which could threaten that state’s avocado industry. California grows about 90 percent of the avocados in the United States, and Florida is the number-two producer.

“The information we will provide may help their scientists, regulatory agencies and producers prepare for the potential introduction of laurel wilt into California,” said Jonathan Crane, a UF/IFAS professor of horticultural sciences and tropical fruit Extension specialist. “The networking among Florida and California scientists and Extension faculty may provide new ideas that lead to control tactics for this deadly fungal-ambrosia beetle complex.”

UF/IFAS faculty will tell their counterparts and industry leaders about their latest research findings and Extension efforts to combat laurel wilt. Originally, UF/IFAS researchers thought the redbay ambrosia beetle transmitted laurel wilt. Then they found out several related beetles could transmit the fungus to avocado trees – and the redbay ambrosia was not a primary carrier.

Daniel Carrillo, a UF/IFAS assistant professor of entomology, is trying to pinpoint the beetle species that infects the trees. Carrillo has found more than 14 ambrosia beetles may infest avocado trees, and he is studying them to identify key players in the spread of this disease and working on ways to control them. Beetle control is important, but management practices for these beetles periodically change because of ongoing research.

In addition, Crane is telling his counterparts in California about his outreach work with South Florida avocado growers.

“Specifically, we are providing the California industry with recommendations: scouting to detect trees symptomatic for laurel wilt and then implementing sanitation procedures without delay,” Crane said. “This is the most reliable way to prevent the spread of the pathogen through root grafts among trees and eliminates the ambrosia beetle vector breeding sites.”

Other measures such as prophylactic systemic fungicide treatments work but must be applied before infection with the pathogen. Limited applications of trunk and major limb contact insecticides help to reduce beetle vector populations, Crane said

With an estimated 40,000 commercial avocado trees already destroyed by laurel wilt in Florida, growers need a solution, Crane said. The 40,000 trees account for about 5 percent of the commercial avocado trees grown in Florida. More than 98 percent of Florida’s commercial avocados are grown in Miami-Dade County, but avocado trees are popular in residential landscapes too.

In addition to perhaps several types of beetles infecting avocado trees with laurel wilt, the pathogen is spread through the interconnected roots of mature avocado trees. The time from infection to tree mortality ranges from four to eight weeks.

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