A test of possible indirect mediation of wound-induced resistance in cabbage against Pieris brassicae

Direct wound-induced effects on insect herbivores have received much attention and criticism. However, studies of indirect effects are rarer. Previous work has indicated that herbivores on cabbage do not show direct effects of wound-induced resistance. We tested whether cabbage has more indirect mechanisms of wound-induced resistance against a common herbivore Pieris brassicae. The proposed mechanisms were that elevated production of defensive/resistant chemicals in leaves might (1) reduce growth rates thereby increasing the window of vulnerability to parasitoids, (2) enhance the pathogenic effects of Bacillus thuringiensis and (3) render plants previously wounded less attractive to ovipositing females. No evidence could be found in support of any of these hypotheses. There was a trend for increased oviposition on wounded plants. The implications of these results for studies of wound-induced effects are discussed.