Scientists seek clues to ambrosia beetle control in avocados

10/03/2012 03:00:00 PM
Vicky Boyd

redbay ambrosia beetle trappingCourtesy Agricultural Research ServiceEntomologist Paul Kendra hangs a trap to try to catch redbay ambrosia beetles.With a deadly avocado disease knocking on their door, Agricultural Research Service scientists in Miami are scrambling to try to find ways to control it and the beetle that transmits it.

The redbay ambrosia beetle and the laurel wilt fungus it carries have been confirmed in Miami-Dade County, according to a news release.

The disease is 90 percent to 95 percent fatal to avocados and related trees, such as redbay.

The redbay ambrosia beetle has spread to the Carolinas and Mississippi, and researchers are concerned it will soon reach California and Mexico's avocado-producing regions.

They're treating trees in the collection with fungicides to slow the disease, and they're shipping healthy trees to disease-free sites to perpetuate the collection.

In the meantime, researchers are trying to develop a chemical attractant.

Previous work has shown that the beetle sniffs out volatile compounds.

In field trials, the researchers compared the efficacy of manuka oil lures, phoebe oil lures and bolts of wood cut from lychee and from three races of avocado trees.

They also conducted laboratory trials to see what types of wood the beetles preferred and then analyzed the compounds the wood released using gas chromatography-mass spectroscopy.

The researchers found the beetles were most attractive to lychee and had no strong preferences among the three different avocado races.

Of 29 compounds detected, three were attractive to beetles, and lychee had large amounts of all three.

Subsequent research found phoebe oil lures lasted 10-12 weeks, while manuka lures lasted only 2-3 weeks.

Researchers also found beetles prefer freshly cut wood, which means trees are more vulnerable right after pruning before the cuts heal over.



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