Hybrid Poplar Genotype Affects Attack Incidence by the Poplar-and-Willow Borer (Cryptorhynchus lapathi)

Abstract

Increasing incidence of the poplar-and-willow borer (Cryptorhynchus lapathi) in Pacific Northwest hybrid poplar plantations has resulted in reduced wood quality and stem breakage. Three replicated, 5-yr-old clone trials established in the vicinity of Pullman, WA were rated for host attack preference. Attacks by C. lapathi were found to be significant for plantation, clone, and the clone by plantation interaction. Attack rating among clones was affected by genotype. Those clones possessing P. nigra parentage, including Lombardy poplar, OP-367, and PC-6, showed significantly lower attacks across all plantations. Within the P. trichocarpa × P. deltoides (TD) hybrids, both 58-280 and 50-194 consistently exhibited lower attacks compared to the remaining four TD hybrids. Plantation, clone, and the plantation by clone interaction affected tree growth parameters significantly. Mean clone stem volume across sites from largest to smallest was: 49-177, OP-367, 50-197, 52-225, PC-6, 50-194, 58-280, 15-29, and Lombardy poplar. Attempts to correlate attack rating with any parameter of tree size were unsuccessful. Combining growth data and attack rating, OP-367 would be recommended for planting in arid regions east of the Cascade Mountains, followed by PC-6, 50-194 and 58-280. Future hybrid poplar breeding for this region should consider P. nigra as a parent.