HOST-PLANT CHEMISTRY AND PREFERENCES IN EGG-LAYING TRIOZA-APICALIS (HOMOPTERA, PSYLLOIDEA)

Sixteen species belonging to the family Apiaceae were examined for the ir acceptance as host plants by Trioza apicalis in non-choice tests. T he number of eggs laid per day varied from 18 on Daucus carota subsp, sativus to zero on Aegopodium podagraria. In a comparative test, the p syllids landed significantly faster and started egg-laying earlier on carrots (D. carota subsp, sativus) than on dill (Anethum graveolens). In a study of shelter plants for T. apicalis, the psyllids survived on spruce, Picea abies, for more than 30 weeks, but they died on grass, Phleum pratense and Brachypodium sylvaticum, within 2 weeks. The lengt h of the day is one of the factors regulating hibernation. At 20 degre es C, light regimes shorter than 17 h induced hibernation, while longe r light periods led to reproduction. Both the shelter plants and the s ummer hosts, including the Apiaceae species, released large amounts of monoterpene hydrocarbons, with great differences among the species. T he most preferred host plants (carrots) were found to contain (+)- and (-)-alpha-pinene and (+)-sabinene, while large amounts (>20%) of eith er (+) or (-)-limonene were released by the species of low preference. (-)-alpha-Pinene, (-)-beta-pinene, and (-) limonene were the main com ponents of the spruce odour. A multivariate data analysis of the chemi cal results showed clearly the significant similarities of the summer host and shelter plants (Daucus carota, Picea abies, and Juniperus com munis). (C) 1997 Elsevier Science Ltd.