Objective The frequent occurrence of pests and diseases in poplar plantations has become a key bottleneck restricting the sustainable development of the industry. Breeding insect-resistant varieties is an important way to be environmentally friendly. This study aims to systematically evaluate the resistance of 94 poplar clones to trunk borers and foliage-feeding pests, screen insect-resistant germplasms, and provide a scientific basis for genetic improvement of poplar and regional sustainable development.

Method Taking 94 7-year-old poplar clones in Yushutai Forest Farm of Lishu County, Jilin Province as experimental materials, field surveys were conducted on natural damage caused by trunk borers (Saperda populnea, Cryptorhynchus lapathi) and foliage-feeding pests (Cnidocampa flavescens, Rhytidodus poplara, Stauronematus platycerus, Chrysomela populi). The feeding index of Hyphantria cunea larvae of each clone was determined by indoor leaf-disc method. The development indexes such as larval survival rate, weight gain index, prepupal rate and pupation rate were observed by field bagging method. The multi-index comprehensive evaluation of insect resistance was carried out by comprehensive membership function method.

Result (1) The overall incidence rate of stem-boring pests among the 94 tested poplar clones was 92.55%, yet seven clones remained free from damage by both types of trunk borers, indicating that although the pressure of trunk borers in this experimental forest was high, there were high resistance resources that could be excavated. (2) Foliage-feeding pests species occurred with significant imbalance, among which Rhytidodus poplara was the dominant pest. Fifteen poplar clones, including T521 and T726, remained completely free from damage by the four defoliating pests, demonstrating broad-spectrum resistance to defoliating insects. (3) The feeding index of Hyphantria cunea larvae varied significantly among different clones (F = 9.451, P = 0.000), indicating a high level of variation. Among them, clones T722 and T717, which have lower feeding indices, serve as elite germplasm and can be used for breeding insect-resistant varieties. (4) Based on the effects on the development of Hyphantria cunea larvae in the bagging and insect inoculation test, the 94 poplar clones can be divided into three categories: strongly inhibiting (28 clones), inhibiting (26 clones), and highly susceptible (40 clones). (5) Through comprehensive evaluation using the membership function method, ten poplar clones including T717, T421, and T731 were identified as the top-ranked in terms of overall resistance. Among them, clones T717, T421 exhibited consistently high resistance under both indoor feeding conditions and field infestation conditions, achieving broad-spectrum resistance to different pest types.

Conclusion The poplar clone population constructed through hybridization contains abundant insect-resistant genetic variation. The clones T717 and T421 selected in this study exhibited outstanding performance under both natural field conditions and artificial infestation conditions, demonstrating composite resistance to multiple pests. They can serve as core parents and promising materials for insect resistance breeding for deployment in poplar plantations in Northeast China, providing important germplasm support for the sustainable management of China’s poplar industry.