University of Florida (UF) scientists believe they have found what could be the first biological control strategy against laurel wilt, a disease that threatens the state’s US$54m avocado industry.
Red ambrosia beetles bore holes into healthy avocado trees, bringing with them the pathogen that causes laurel wilt. Growers control the beetles that carry and spread laurel wilt by spraying insecticides on the trees, said Daniel Carrillo, an entomology research assistant professor at the Tropical Research and Education Center in Homestead.
But a team of researchers from the Tropical REC and the Indian River Research and Education Center in Fort Pierce have identified a potential biological control to use against redbay ambrosia beetles that could help growers use less insecticide.
First, they exposed beetles to three commercially available fungi, and all of the beetles died. Then they sprayed the fungi on avocado tree trunks, and beetles got infected while boring into the trunk. About 75 per cent of those beetles died, said Carrillo, an Institute of Food and Agricultural Sciences faculty member.
Ideally, the fungal treatments could prevent beetles from boring into the trees, eliminating the risk that the pathogen would enter the trees, the study said. But tests showed female beetles bored into the trees and built tunnels regardless of the treatment. Still, researchers say their treatment can prevent the female beetles from laying eggs.
UF/IFAS scientists don’t know yet how much less chemical spray will be needed to control the redbay ambrosia beetle. But Carrillo sees this study as the first step toward controlling the beetle in a sustainable way.
“When you want to manage a pest, you want an integrated pest management approach,” Carrillo noted. “This provides an alternative that we would use in combination with chemical control.”
The redbay ambrosia beetle -- native to India, Japan, Myanmar and Taiwan -- was first detected in 2002 in southeast Georgia. It was presumably introduced in wood crates and pallets, and its rapid spread has killed 6,000 avocado trees in Florida, or about 1 per cent of the 655,000 commercial trees in Florida. The beetle was first discovered in South Florida in 2010.
Most American-grown avocados come from California, with the rest coming from Florida and Hawaii. The domestic avocado market is worth US$429m, according to Edward Evans, a UF associate professor of food and resource economics, also at the Tropical REC. Florida’s avocados are valued at about US$23m, or about 5 per cent of the national market.
