A View of Diel Variation of Maize Odorscape

Volatile organic compounds (VOCs) released by host plants attract gravid European corn borer (ECB) female moths for oviposition. Despite extensive studies, little is known about VOCs emitted by maize under natural conditions or the odorscape of a maize field, particularly at the time of ECB oviposition. Here, we characterized VOCs released by undamaged maize plants and VOCs in the maize field odorscape. VOCs were collected throughout the diel cycle with solid-phase microextraction fibres. VOCs were identified by GC-MS and quantified with calibration curves. Four replicates per time period were collected; i.e., dusk, night, dawn, and day. VOC patterns differed between the maize plants and the maize field odorscape throughout the diel cycle. At night, the period of ECB oviposition, the VOC pattern was characterized by an increase in monoterpenes, a decrease in sesquiterpenes, and the presence of methyl salicylate, α-copaene, and Z-3-hexenyl acetate. An apparent discrepancy between maize plant and field odorscape VOC compositions was observed. Key compounds were identified as putative host-cues, including methyl salicylate, α-pinene, 3-carene, p-cymene, limonene, and dimethyl nonatriene. This study showed that VOCs were released by maize in a diel pattern, and host-characteristic cues were present for nocturnal ECB oviposition.