ADULT RESPONSE OF THE ALMOND SEED WASP, EURYTOMA-AMYGDALI, TO CHEMICALS FROM ITS HOST AND CERTAIN NONHOSTS

Females of the almond seed wasp, Eurytoma amygdali Enderlein (Hymenopt era, Eurytomidae), responded in an olfactometer positively to odours f rom almond flowers and unripe fruits, but not to almond leaf odours an d odours from flowers and unripe fruits of certain other nonhost Prunu s species. Males responded to none of these odours. Extracts of undama ged unripe almond fruits (using ethanol, methanol, acetone, hexane, di chloromethane, or petroleum ether) stimulated female aggregation on gl ass surfaces treated with these extracts; in addition, certain fruit e xtracts (ethanol, methanol, or acetone) stimulated oviposition. Extrac ts of undamaged almond leaves (ethanol, methanol, or acetone) and flow ers (ethanol or methanol) also stimulated female aggregation and ovipo sition. Aggregation and oviposition in response to an ethanol extract of almond fruits was intense in females aged 5 to 14 days and from 12: 00 to 18:00 h (photophase between 06:00 and 20:00). Certain almond fru it (ethanol, methanol, acetone or hexane) and flower extracts (ethanol or methanol) also provoked female response in the olfactometer. The r esults strongly suggest that certain chemical stimuli emanating from p arts of the almond tree play a major role in host selection and ovipos ition. Some of the extracts tested may be a good source for the isolat ion, identification and synthesis of compounds stimulating attraction, aggregation and oviposition in nature.