Comparative headspace analysis of cabbage plants damaged by two species of Pieris caterpillars: consequences for in‐flight host location by Cotesia parasitoids

Abstract

Headspace composition, collected from intact cabbage plants and cabbage plants infested with either Pieris brassicae L. or P. rapae L. (Lepidoptera: Pieridae) first instar larvae, was determined by GC‐MS. Twenty‐one volatiles were identified in the headspace of intact plants. Twenty‐two volatiles were identified in the headspace of plants infested by P. brassicae larvae, 2 of which, Z‐3‐hexenyl butyrate and Z‐3‐hexenyl isovalerate, were not detected in the headspace of either intact or P. rapae damaged plants. In the headspace of the latter, 21 compounds were identified, all of which were also produced by intact plants. No significant quantitative differences were found between headspace composition of the plants damaged by one or the other caterpillar species. Major differences between intact and caterpillar‐damaged plants in contribution to the headspace profile were revealed for hexyl acetate, Z‐3‐hexenyl acetate, myrcene, sabinene and 1, 8‐cineole. The larval endoparasitoid Cotesia glomerata L. was attracted by the volatiles emanating from B. oleracea damaged by P. brassicae first instar larvae. C. rubecula L., a specialized larval endoparasitoids of P. rapae, was attracted by the volatiles released from the B. oleracea ‐ P. rapae plant‐host complex. This shows that cabbage plants kept under the conditions of headspace collection produce attractive volatiles for both parasitoids.

Variation In Plant Volatiles and Attraction Of The ParasitoidDiadegma semiclausum(Hellén)

“…Our results also suggest that D. semiclausum assesses changes in volatile blends as a result of herbivore damage. The odor blend of infested Brussels sprout was similar to that of uninfested Brussles sprout, but many of the compounds were emitted in higher amounts by infested plants, which was in line with findings of other studies (Blaakmeer et al, 1994;Geervliet et al, 1997;Reddy and Guerrero, 2000;Smid et al, 2002). Compounds like (Z)-3-hexen-1-yl acetate, (Z)-3-hexen-1-ol, and limonene, which were also detected in our samples, could play a role in the attraction of the parasitoids C. rubecula, C. glomerata, and C. plutellae, and of the predatory lacewing Chrysoperla carnea (Geervliet et al, 1997;Reddy et al, 2002;Smid et al, 2002).…”

“…However, among the 59 compounds released by infested • -compound detected by Mattiacci et al, 1994; × -compound detected by Tollsten and Bergström, 1988;# -compound detected by Blaakmeer et al, 1994; -compound detected by Agelopoulos and Keller, 1994; •-compound detected by Shiojiri et al, 2001. Table 1.…”

“…This indicates that subtle differences in volatile profiles of uninfested plants could be important in the attractivity of these plants for D. semiclausum. Brussels sprout plants damaged by hosts are more attractive for the parasitoids Cotesia glomerata, C. rubecula, and C. plutellae than artificially damaged or intact Brussels sprout plants (Steinberg et al, 1992(Steinberg et al, , 1993Blaakmeer et al, 1994;Geervliet et al, 1996;Shiojiri et al, 2000). A recent study by Ohara et al (2003) showed that D. semiclausum females were attracted by the odor blends of uninfested and infested cruciferous plants.…”

“…Some alcohols and terpenoids emitted by mustard were present in this species only, and some alcohols, esters, and indole were detected both in mustard and infested Brussels sprout. The GLV (Z)-3-hexen-1-yl acetate is known to be produced by herbivore-infested Brussels sprout in greater quantities than by uninfested plants (Blaakmeer et al, 1994;Mattiacci et al, 1994;Geervliet et al, 1997). This was the dominant compound that mustard produced.…”

“…The volatile profile of Plutella-infested Brussels sprout shares many similarities with the odor profiles from white cabbage and Brussels sprout infested by different Pieris spp. (Geervliet et al, 1997;Blaakmeer et al, 1994). Moreover, parasitoid species associated with P. xylostella and Pieris spp.…”