1CABI Bioscience Centre, Delémont, Switzerland.
2Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY 14853, USA.
3State University of New York, Stony Brook, USA.
4Department of Entomology, Pennsylvania State University, USA.
Biological Control, i.e. the deliberate use of natural enemies to control weeds or insect pests, has become an important tool in regulating exotic invasive species. In order to reduce the risk of non-target effects the biocontrol candidate should have a very narrow host-range. The lily leaf beetle, Lilioceris lilii, has become an important ornamental pest both in part of its native European as well as in its naturalized North American range. The larval parasitoid Lemophagus pulcher is supposed to be specific enough to be released into North America to reduce lily leaf beetle densities. In order to interpret the data of the basic testing of its physiological and behavioural host-range, behavioural studies have been initiated to elucidate the chemical cues which are used by L. pulcher in host finding and acceptance. Both naive and experienced females are attracted by a whole range of sources, including damaged leaves, oral droplets, fecal shields which the larvae carry with themselves, and the larval bodies. The fecal shield seems to play a key role as an oviposition stimulant, since larvae of the lily leaf beetle and of a non-host species are equally attacked when they are covered by the fecal shield of the lily leaf beetle. Fractionation of a methanol-extract of this shield revealed that only dummies treated with the polar fractions induced oviposition behaviour in L. pulcher. The origin and specificity of the different cues will be discussed with regard to the potential of host-range expansion once this parasitoid species becomes naturalized in North America.