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 a ttention and criticism. However, studies of indirect effects are rarer . Previous work has indicated that herbivores on cabbage do not show d irect effects of wound-induced resistance. We tested whether cabbage h as more indirect mechanisms of wound-induced resistance against a comm on herbivore Pieris brassicae. The proposed mechanisms were that eleva ted production of defensive/resistant chemicals in leaves might (1) re duce growth rates thereby increasing the window of vulnerability to pa rasitoids, (2) enhance the pathogenic effects of Bacillus thuringiensi s and (3) render plants previously wounded less attractive to oviposit ing females. No evidence could be found in support of any of these hyp otheses. There was a trend for increased oviposition on wounded plants . The implications of these results for studies of wound-induced effec ts are discussed.