Electroantennogram and behavioural responses of Plutella xylostella to volatiles from the non‐host plant Mentha spicata

Abstract

Plutella xylostella Linnaeus (Lepidoptera: Plutellidae) is one of the most important pests of cruciferous vegetables. Mechanically damaged Mentha spicata Linnaeus (Lamiales: Lamiaceae) strongly repels P. xylostella adults; however, the repellent mechanism remains unclear. In this study, the repellent mechanism was explored based on the electroantennogram (EAG) and behavioural responses of P. xylostella to volatiles from the damaged M. spicata. First, the active volatile compounds in the headspace volatiles of damaged M. spicata were identified by gas chromatography‐electroantennographic detection (GC‐EAD) and gas chromatography–mass spectrometry (GC–MS). Furthermore, the EAG and behavioural responses of P. xylostella to these compounds were investigated. The GC‐EAD results indicated that four compounds, 2,4‐dimethylheptane, 4‐methyloctane, 2‐methylnonane, and myrcene induced EAG responses in female antennae. 2‐methylnonane and myrcene elicited strong dose‐dependent EAG responses starting at a dose of 1 μg/μL. Choice tests in a four‐arm olfactometer showed significant repellent effects of the four compounds on P. xylostella adults at 100 μg/μL, and the repellent indices of 2,4‐dimethylheptane, 4‐methyloctane, 2‐methylnonane, and myrcene were 70.0%, 76.7%, 66.7%, and 73.3% to mated females, respectively. Finally, oviposition repellence assays showed that female adults were significantly repelled by these compounds, and the oviposition repellent index for myrcene was 23.9%. 2,4‐dimethylheptane, 4‐methyloctane, 2‐methylnonane, and myrcene mediate the repellence of wounded M. spicata to P. xylostella adults, suggesting that the four compounds contribute towards developing behavioural regulators of this important pest.

Identification and evaluation of cruciferous plant volatiles attractive to Plutella xylostella L. (Lepidoptera: Plutellidae)

“…Collection of headspace volatiles from seven host plants with four or five leaves was performed separately as previously described with minor modifications. 18 All glassware was washed with distilled water, rinsed with acetone, and finally dried at 100 °C overnight before use. Unwounded plant leaves were detached and each was evenly cut into two or three pieces using clean scissors, about 4-5 g were then put into a clean sampling jar with an air inlet pipe and an air outlet pipe.…”