Differing Behavioural Responses of Bemisia tabaci MEAM1 and MED to Cabbage Damaged by Conspecifics and Heterospecifics

The whitefly Bemisia tabaci is a serious pest with an extensive host range. Previous research has shown that B. tabaci is a species complex with many cryptic species or biotypes and that the two most important species are MEAM1 (Middle East-Minor Asia 1) and MED (Mediterranean genetic group). MEAM1 and MED are known to differ in their preference for cabbage, Brassica oleracea, as a host plant, however, the mechanism underlying this preference is unknown. In the current study, a host choice experiment showed that MED prefers to settle and oviposit on undamaged cabbage plants rather than MED-damaged cabbage plants. However, MEAM1 prefers MED-damaged cabbage plants to undamaged plants and does not exhibit a significant preference for undamaged or MEAM1-damaged cabbage plants. On the basis of gas chromatography-mass spectrometry (GC-MS) analysis, the following volatiles were released in larger quantities from Q-damaged cabbage plants than from undamaged plants: 2-ethyl-1-hexanol, benzenemethanol, (E)-2-decenol, benzaldehyde, nonanal, acetic acid geraniol ester, 4-hydroxy-4-methyl-2-pentanone, decane, and α-longipinene. Only one volatile, 4-hydroxy-4-methyl-2-pentanone, was released in greater quantities from MEAM1-damaged cabbage plants than from undamaged plants. Our results suggest that differences in herbivore-induced host volatile release may help explain the differences between the preference of B. tabaci MEAM1 and MED for cabbage as a host.