Estimating the effect of poplar resistance on the performance of the woolly poplar aphid, Phloeomyzus passerinii, in various experimental conditions

The woolly poplar aphid, Phloeomyzus passerinii (Signoret) (Sternorrhyncha: Aphididae), causes the most damage to poplars in southern Europe and the Near East as outbreaks can lead to massive mortality in mature stands. Previous studies, conducted on poplar cuttings or young trees, showed that resistance varied depending on the poplar genotype. However, these results did not indicate how aphid populations were affected by tree resistance and were only partially confirmed by field observations. This study investigated the effect on aphid settlement and performance of poplar genotypes belonging to Populus x canadensis Moench, Populus x interamericana Brockh., Populus nigra L., Populus deltoides Bartram ex Marshall, and Populus trichocarpa Torr. & A. Gray ex Hook. using a single aphid clone. The study was conducted under three experimental conditions: (i) unrooted cuttings, (ii) potted cuttings, and (iii) mature trees. The aphid settlement rate, the larval development rate, and the fecundity were affected by the poplar genotype, highlighting the antixenotic and antibiotic properties involved in tree resistance to P. passerinii. The laboratory results for aphid performance and settlement rate on unrooted cuttings were transposable to both potted cuttings and mature trees. Laboratory studies could, therefore, provide useful information for identifying the parameters involved in resistance mechanisms.