[en] Feeding responses by Scolytus scolytus were tested using elm twig bark extracts in a laboratory bioassay. One to 4- years-old elm twigs or small branches were sampled in spring and their bark extracted separately with methanol and with a mixture of petroleum ether and diethyl ether (1:1) as solvents. Bark extracts were tested in a two choice feeding bioassay consisting of two polyurethane discs placed in a 10 cm diameter Petri dish. Extracts were applied onto the discs and the amount of disc eaten by ten freshly emerged S. scolytus adults was recorded after 24 hours. Ten U. minor, two U. laevis, six U. glabra, three Dutch hybrids (European x Asiatic) and one U. pumila trees were tested in several comparisons. Discs with extracts from both U. laevis trees were significantly less eaten than those from U. pumila or from U. minor trees in two choice tests. Similarly, extracts from all U. glabra trees received less feeding than those from U. minor. On the contrary, S. scolytus showed no difference in feeding between U. pumila and U. minor extracts, and similarly for Dutch hybrids in comparison with two U. minor clones. Again, beetles preferred to feed on Dutch hybrid extracts better than in those from U. laevis. Significant intraspecific differences in feeding were obtained in U. minor. One of the U. minor clones resulted less chosen when compared to other four trees. Extracts from a dying U. minor tree received more feeding than those from a healthy tree. Comparisons were also made between bark extracts from 2-to 4-year-old vs. current-year twigs within the same trees. In one of the four U. minor tested, a significant preference for the older twig extracts was recorded.

[es] Se estudi&oacute; la respuesta de alimentaci&oacute;n de S. scolytus a extractos del floema de ramillas de olmo en bioensayos de laboratorio. Se muestrearon en primavera ramillas de olmo de uno a cuatro a&ntilde;os de edad y su floema fue extra&iacute;do independientemente con metanol o con una mezcla de eter de petr&oacute;leo y eter diet&iacute;lico (1:1). Los extractos del floema se evaluaron en un bioensayo de doble elecci&oacute;n consistente en dos discos de poliuretano dispuestos en una placa Petri de 10 cm de di&aacute;metro. Se aplicaron los extractos a los discos y se midi&oacute; la superficie de disco comida por diez adultos reci&eacute;n emergidos de S. scolytus durante 24 h. Se ensayaron diez U. minor, dos U. laevis, seis U. glabra, tres h&iacute;bridos holandeses (europeo x asi&aacute;tico) y un U. pumila en diversas comparaciones. Los discos con extractos de ambos U. laevis fueron significativamente menos comidos que aqu&eacute;llos con los de U. pumila o de U. minor. Igualmente, los extractos de todos los U. glabra recibieron menor alimentaci&oacute;n que aqu&eacute;llos de U. minor. Por el contrario, S. scolytus no mostr&oacute; preferencias entre los extractos de U. minor y de U. pumila, e igualmente, entre los de U. minor y los de h&iacute;bridos holandeses. Nuevamente, los escol&iacute;tidos prefirieron alimentarse menos de los extractos de U. laevis que de los h&iacute;bridos holandeses. Se encontraron diferencias intraespec&iacute;ficas significativas en U. minor. Uno de los clones de U. minor result&oacute; menos preferido cuando se le compar&oacute; con otros cuatro &aacute;rboles. Los extractos de un U. minor moribundo recibieron mayor alimentaci&oacute;n que los de un &aacute;rbol sano. Se realizaron comparaciones entre los extractos del floema de ramillas de 2 a 4 a&ntilde;os de edad y de ramillas del a&ntilde;o en curso de un mismo &aacute;rbol. En uno de cuatro U. minor ensayados se observ&oacute; una preferencia significativa por los extractos de las ramillas m&aacute;s viejas.