L. Messchendorp et al., Behavioural observations of Pieris brassicae larvae indicate multiple mechanisms of action of analogous drimane antifeedants, ENT EXP APP, 95(3), 2000, pp. 217-227
We tested 11 analogous synthetic drimane antifeedant compounds for their fe
eding inhibiting effects on larvae of the large white butterfly Pieris bras
sicae L. (Lepidoptera: Pieridae) in no-choice tests on the host plant Brass
ica oleracea L. Furthermore, we observed larval feeding behaviour in no-cho
ice tests to analyze temporal effects of five drimanes. The results show th
at the five analogous antifeedants differentially influence feeding behavio
ur and locomotion activity. Warburganal and polygodial are most likely sens
ory mediated antifeedants. Habituation to these compounds occurs soon after
the onset of the tests (i.e., within 0.5-1.5 h). Compound 5 and confertifo
lin are probably not direct, sensory mediated antifeedants. After 0.5-1.5 h
of exposure, these compounds inhibit not only feeding, but also locomotion
behaviour, indicating postingestive, toxic effects. Isodrimenin inhibits f
eeding from the onset of the test and is probably a sensory mediated antife
edant. No habituation occurs to this compound, indicating that isodrimenin
is either a very strong antifeedant or that it additionally has postingesti
ve, toxic effects. Topical application of the drimanes on the larval cuticl
e revealed feeding inhibiting effects, but these could not be related to th
e occurrence of postingestive feeding inhibiting effects, indicating that t
his method is inappropriate to show possible postingestive effects of drima
nes in P. brassicae. In conclusion, the behavioural observations performed
in this research indicate that analogous drimanes inhibit feeding by P. bra
ssicae larvae through multiple mechanisms of action. The results show that,
when developing a structure activity relationship (SAR) for a series of an
tifeedants, it is important to distinguish the mode of action which underli
es inhibition of feeding.