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[(Populus trichocarpa Torr. & Gray · Populus deltoides Bartram ex Marshall) · P. deltoides] (TD · D) and
[(P. trichocarpa · Populus maximowiczii Henry) · (P. trichocarpa · P. maximowiczii)] (TM · TM), previously reported
as susceptible and resistant, respectively, are described. Laboratory experiments showed that in naturally waxed
leaves of the resistant hybrids, aphids devoted less time to probing and more time to non-probing behaviour when
compared with their behaviour on susceptible hybrids. These differences were not present when leaves of these hybrids
were experimentally dewaxed. A field experiment demonstrated that aphid reproductive performance was affected by
hybrid genotype (higher in the TD · D) but not by EWs, although a trend of lower performance on dewaxed leaves in
both hybrids was apparent. SEM analysis of EWs revealed micromorphological differences between both hybrids.
These results support the idea that EWs affect aphid behaviour in poplars, with a rather slight impact on reproductive
performance.
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