Euwallacea perbrevis is an ambrosia beetle that vectors fungal pathogens causing Fusarium dieback in Florida avocado trees. Current monitoring lures contain quercivorol, a fungus-produced volatile, but the exact attractant is… Click to show full abstract
Euwallacea perbrevis is an ambrosia beetle that vectors fungal pathogens causing Fusarium dieback in Florida avocado trees. Current monitoring lures contain quercivorol, a fungus-produced volatile, but the exact attractant is unknown since lures contain a mixture of p-menth-2-en-1-ol isomers and both α- and β-phellandrene. This study used pure cultures of six symbiotic fungi isolated from E. perbrevis to document volatile emissions and determine the relative attraction of symbionts in binary choice assays. In a comparative test, headspace solid-phase microextraction followed by gas chromatography–mass spectroscopy was used to identify and quantify emissions from 3-week-old cultures. In a temporal study, Super-Q collection followed by gas chromatography–flame ionization detection was used to measure cis- and trans-p-menth-2-en-1-ol emissions for three months. A total of 15 compounds were detected, with monoterpene hydrocarbons and oxygenated monoterpenoids predominating. Only trans-p-menth-2-en-1-ol was common to all six symbionts. Peak levels of both isomers were observed at day 7, then gradually declined over a 90 day period. In choice tests, avocado sawdust disks inoculated with Fusarium sp. nov. were the most attractive. This symbiont produced only two volatiles, trans-p-menth-2-en-1-ol and limonene. The combined results indicate that trans-p-menth-2-en-1-ol is the primary female attractant emitted from symbiotic fungi, but limonene may be a secondary attractant of E. perbrevis.
               
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