Identification and Evaluation of Alfalfa Volatiles for Monitoring and Management of Odontothrips loti and Frankliniella occidentalis

Plant-derived volatile organic compounds (VOCs) are widely used as insect attractants for population monitoring, offering an efficient and eco-friendly approach to pest management. Since thrips are the dominant pest species in alfalfa (<i>Medicago sativa</i>) crops, alfalfa volatiles produced in the presence of <i>Odontothrips loti</i> and compounds with attractive potential to both <i>O</i>. <i>loti</i> and <i>Frankliniella occidentalis</i> were investigated. Using gas chromatography-mass spectrometry (GC-MS), 96 VOCs were identified from seven alfalfa cultivars with varying levels of thrips resistance with and without damage by <i>O</i>. <i>loti</i>. Eleven volatiles were selected for Y-tube olfactometer assays. The semiochemical <i>p</i>-Menth-8-en-2-one, which was suppressed in alfalfa subject <i>O</i>. <i>loti</i> damage, significantly attracted both <i>O</i>. <i>loti</i> and <i>F</i>. <i>occidentalis</i> in Y-olfactometer bioassays; the response rates were 2.05~3.07 times compared to control (<i>p</i> < 0.05). Further experiments confirmed <i>p</i>-Menth-8-en-2-one, dispensed through PE (Polyethylene) vials, was the most effective lure material with the concentrations of 10 ng/μL. This study demonstrated that the alfalfa-derived volatile <i>p</i>-Menth-8-en-2-one, shows significant attraction to thrips, which can be utilized for monitoring and management of <i>odontothrips loti</i> and <i>frankliniella occidentalis</i>.