Shivaphis celti: An ongoing study of the biology, distribution, and impact of a non-native aphid on Celtis laevigata

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Emilee M. Poole, Entomology, University of Georgia, Athens, GA, Michael D. Ulyshen, USDA Forest Service, Athens, GA and Scott Horn, US Forest Service, Athens, GA

Background/Question/Methods
Sugarberry (Celtis laevigata Willd.), is a tree native to the US, and the species has been dying in the southeastern US since first reported in 2009 in Columbia, SC. The unexplained sugarberry (Celtis laevigata) mortality has been ongoing for over a decade, which represents one of the most severe and widespread Celtis mortality episodes reported in North America. During early investigations of dying sugarberry, high numbers of hackberry woolly aphids (Shivaphis celti Das) were recorded, and since initial observations, this species is regularly found feeding on trees with declining health. In addition to the impact of foliage feeding, honeydew production results in thick layers of sooty mold forming on leaves, which appears to be associated with premature leaf fall. Since little is known about the non-native aphid and its potential impact, we aim to understand its distribution and host damage, as well as potential management strategies through literature reviews and an insecticide trial with analysis of nonstructural carbohydrates (NSC) in the roots of potted sugarberry trees.
Results/Conclusions
While collections and reports are limited, S. celti originated in central and southeast Asia, where it feeds on Celtis, and in its native range, this species is not known to cause major damage. The first report of S. celti on Celtis in the western hemisphere was from South Carolina in the United States in 1996, and the aphid has been observed throughout the southeast and in other regions of the US. S. celti is the only member of its genus currently found in the western hemisphere. At this time, our findings suggest imidacloprid is an effective strategy for aphid control, and analysis of root NSC is underway. Although a primary cause of sugarberry mortality is not currently known, we are continuing to investigate S. celti. Non-native insect pests are often cause for alarm, as introduced species frequently have unknown consequences to our native species, and severe mortality events have the potential to change forest structure and composition.