Feeding preferences of woodpigeons and flea-beetles for oilseed rape and turnip rape

Winter turnip rape Brassica rapa ssp. oleifera was shown to have reduced pa latability to woodpigeons, enhanced susceptibility to adult flea beetle fee ding and reduced susceptibility to larval flea-beetle infection when compar ed with winter oilseed rape (B. napus) cultivars in field trials. Levels of leaf waxes were negatively correlated with feeding preferences of adult fl ea beetles. Analysis of volatiles from damaged leaves showed that while all cultivars produce a similar range of nitriles, cyanoepithioalkanes and iso thiocyanates, derived from 3-butenyl, 4-pentenyl and phenylethyl glucosinol ates, B. rapa leaves produced relatively high levels of 1-methylpropyl isot hiocyanate, although there was significant plant-to-plant variation. The po ssible involvement of this mustard oil glycoside and variation in epicuticu lar waxes in plant-herbivore interactions are discussed.