The large white butterfly, Pieris brassicae L., a herbivorous pest of crucifers, produces egg-associated chemical markers that inhibit its oviposition. The identification of the marker compounds is reported herein. Separation by means of reversed-phase hplc demonstrated the presence of three active substances, which were identified as tra»j-2- [3-(3,4,5- and trans-2-[3-(3,4dihydraxyphenylpropenoyl)amino]-3,5-dihydroxybenzoic acid [31, using mass and nmr spectroscopy and chemical synthesis. This group of compounds has not been reported from the animal kingdom before. The same compounds are produced by two related Pieris species. This is the first report of taxon-specific compounds affecting butterfly oviposition behavior. The availability, stability, and inhibitory action on colonization of cabbage plants by butterflies make application of these compounds in the protection of cabbage crops feasible and comparable with other environmentally safe crop protection strategies.Females of several herbivorous insect species are known to deposit a marking substance on or near the eggs (1-3). This substance signals to conspecific females (and also to herself if she happens to visit the same site again) that the site is already occupied. This phenomenon constitutes an important element in foraging strategies of herbivorous insects, because it prompts an even distribution of eggs over the available food resources, results in reduction of intraspecific competition, and improves resource exploitation. Because of their important ecological function these host-marking pheromones (HMPs), formerly often labeled as oviposition-deterring pheromones (ODPs), attract much attention. Egg-associated substances also affect related herbivorous species and natural enemies of the herbivores (4-7). Oviposition deterring activity has also been found in feces from larvae (8-10). A more detailed analysis of the ecological role of an HMP requires its chemical identification. Thus far, only a few attempts to identify eggassociated HMPs have been successful (11-13), with a notable example concerning the cherry fruit fly, Rhagoletis cerasi (11).Within the Lepidoptera, several potential uses of HMPs have been reported (14,15). The large white butterfly, Pieris brassicae L., a specialized herbivore of cabbage (Brassica oleráceo) and other cruciferous plants, has been studied in detail (14,16,17). Oviposition by P. brassicae is inhibited when a potential host plant carries conspecific eggs or is sprayed in a methanolic egg wash (14,16). Inhibition of oviposition is especially pronounced when females have a choice between HMP-treated plants and control plants, or when dispersal activity can be manifested (18). Based on a two-choice bioassay, the inhibition of oviposition by egg-associated compounds was quantified (17). Herein the identification and synthesis of HMPs isolated from eggs of P. brassicae is presented.
RESULTS AND DISCUSSIONEggs ofP. brassicae, freshly laid on cabbage leaves, Brassica olerácea L. var. gemmifera