Hybrid poplar clones with Populus maximowimii parentage demonstrate postoviposition antibiosis to Cryptorhynchus lapathi (Coleoptera: Curculionidae)

Damage caused by the poplar-and-willow borer, Cryptorhynchus lapathi (L.) (Coleoptera: Curculionidae), is reported to vary among hybrid poplar clones. We evaluated oviposition preferences and larval success in four hybrid poplars on potted and field-planted trees. Oviposition occurred somewhat less frequently and abundantly on two clones with Populus maximowiczii Henry parentage in field-planted and potted trees, and significantly fewer larvae survived to adulthood on those clones. No adults emerged from field-planted NM 6 (Populus nigra L. X P. maximowiczii) and four emerged from TM 256-28 (Populus trichocarpa Torrey & Gray X P. maximowiczii) on which male-female pairs of C. lapathi had been caged. In contrast, 50 and 140 adults emerged over the same 2-yr period from two susceptible clones (n = 20), TD 52-226 (P. trichocarpa X Populus deltoides Bartram ex Marshall) and TN 302-9 (P. trichocarpa X P. nigra), respectively. Thus, resistance expressed by clones with P. maximowiczii parentage partially involves decreased levels of oviposition, but more significantly, antibiosis in resistant clones prevents the development of larvae, probably in early spring.