©2023 International Society of Arboriculture 38 Arboriculture & Urban Forestry 2023. 49(1):38–53 https://doi.org/10.48044/jauf.2023.004 such as bark peeling, dieback, defoliation, and devel- opment of adventitious roots. As the fi rst step of X. globosa management, assess- ment of infestation by this borer is essential to deter- mine appropriate intervention measures and to monitor the effectiveness of said measures in controlling the infestation. There are 2 common approaches employed in assessment of borer infestation: (1) measurement of symptoms and actual number of borers, and (2) measurement of tree health. Measurements of signs such as exit holes and the actual number of borers can directly estimate the pop- ulation of borers in infested trees. A higher density of exit holes indicates a higher number of emerging INTRODUCTION In Singapore, rain tree Albizia saman [Fabales: Faba- ceae] is among the 10 most common tree species on the island, planted abundantly along roadsides, parks, and gardens. Despite their great adaptability to the local climate, rain trees are susceptible to various insect pests, the most destructive of which is Xystrocera globosa [Coleoptera: Cerambycidae]. Larvae of this species bore into the wood of branches and trunks as they feed, causing extensive damage to internal struc- ture and disrupting nutrient transport (Beeson 1941; Suharti et al. 1994; Matsumoto et al. 2000). As the infestation progresses, trees show constant decline, which over time can manifest into visible symptoms Integrated Visual Assessment Method for Infestation by Lebbek Borer (Xystrocera globosa) in Rain Trees of Singapore By Derrick Nguyen Hoang Danh, Muhammad Izaan bin Istijab, Muhammad Azhari bin Mohammad Zain, Xue Huiyu, Diana Chiu, Varughese Philip, Mei Lai Yap, and Abdul Hamid bin Mohammad Abstract. Background: In Singapore, determining the level of infestation by lebbek borer (Xystrocera globosa)(Olivier, 1795)[Coleoptera: Cerambycidae] is the crucial fi rst step in control of this pestra in rain tree (Albizia saman [Jacq.] Merr.)[Fabales: Fabaceae]. Current assessment methods rely on symptoms such as canopy colour, defoliation, dieback, and actual estimation of borer population via counting of larvae or exit holes created by adults. Currently, there is a lack of systematic approach to integrate different tree health indicators and symptoms to quantify infestation level. This gap poses challenges in assessment of treatment effi cacy as managers could not quantitatively determine whether infes- tation level has changed following treatment. Thus, this study aimed to develop a visual assessment method that can integrate all mentioned symptoms to quantify infestation level. Methods: We surveyed a total of 388 rain trees and used principal component analysis (PCA) to inves- tigate the correlation between X. globosa infestation and different borer infestation symptoms. Borer Infestation Score (BIS) formula was developed based on the linear combinations of the statistically signifi cant principal component. Results: Infestation level was strongly associ- ated with bark peeling, exit holes, and proximity of bark peeling and/or exit holes to trunk base and weakly associated with defoliation, dieback, and canopy colour. Developed BIS formula generated numerical values that distinguished between noninfested and infested trees, refl ected infestation level in surveyed areas and temporal progression of infestation. Conclusions: Described integrated visual assessment method can be executed quickly on fi eld. BIS formula generates quantitative scores easy to be interpreted, tracked, and compared. Keywords. Albizia saman; Borer Infestation Score; Integrated Pest Management; Integrated Visual Assessment; Rain Tree Borer Infesta- tion; Tree Health; Urban Forestry; Xystrocera globosa. Nguyen Hoang Danh et al: Visual Assessment Method for Lebbek Borer Scientifi c Journal of the International Society of Arboriculture
January 2023
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