Assessing potential biological control of the invasive plant, tree-of-heaven, Ailanthus altissima

Tree-of-heaven, Ailanthus altissima, is a deciduous tree indigenous to China and introduced into North America and Europe. It is a serious threat to ecosystems in introduced areas, as the plant is very competitive, and also contains allelopathic chemicals that may inhibit growth of surrounding native plants. In addition, the plant contains secondary chemicals that make it unpalatable to some insects. In this paper we assess potential biological control of this plant by reviewing literature associated with natural enemies of the plant from both its native and introduced regions in the world. Our literature surveys revealed that 46 phytophagous arthropods, 16 fungi, and one potyvirus were reported attacking tree-of-heaven, some apparently causing significant damage in China. Two weevils, Eucryptorrhynchus brandti and E. chinensis, are major pests of the plant in China and are reportedly restricted to tree-of-heaven, showing promise as potential biological control agents. Nymphs and adults of a homopteran insect, Lycorma delicatula and larvae of two lepidopteran species, Samia cynthia and Eligma narcissus, may also cause severe damage, but they are not host specific. Two rust fungi, Aecidium ailanthi J. Y. Zhuan sp. nov. and Coleosporium sp. have been reported on tree-of-heaven in China and are also promising potential candidates for biological control of the plant. Nine insect herbivores and 68 fungi are associated with tree-of-heaven in its introduced range in North America, Europe, and Asia. An oligophagous insect native to North America, the ailanthus webworm, Atteva punctella, may be a potential biocontrol agent for the plant. Among the fungal species, Fusarium osysporum f. sp. perniciosum, caused wilt of tree-of-heaven in North America and may have the potential to control the plant, but its nontarget effect should be carefully evaluated. Our review indicates that there is potential for using insects or pathogens to control tree-of-heaven.