Xylosandrus ambrosia beetles preference of nursery tree species for attacks and colonization under water stress.

Abstract

The role of flood and drought stress on Xylosandrus ambrosia beetle attacks and colonization in nursery trees with varying levels of water stress tolerance has not yet been studied. This study aimed to examine ambrosia beetle preference for tree species varying in their tolerance to water stress. Container-grown dogwoods, redbuds, and red maples were exposed to flood, drought, or sufficient water treatments for 28 d and beetle attacks were counted every third day. Stem tissues were collected at 7 and 14 d after imposing water stress to measure ethanol content using SPME-GC-MS. Trees were dissected to record gallery formation, fungal colonization, presence of eggs, larvae, and adults within the gallery. Additionally, gallery depth was measured. Under flood stress, beetle attacks were found exclusively in dogwood and redbud, with no attacks in red maple. There was a higher number of attacks in dogwood compared to redbud. Gallery formation and depth, fungal colonization, and presence of eggs, larvae, and adults in galleries were higher in dogwood than redbud. About 85% of the adults recovered from galleries were X. crassiusculus and the rest were X. germanus. Among the trees subjected to drought stress, only one dogwood tree had attacks, while the redbuds and red maples had no beetle attack. Tree species assigned to sufficient water were not attacked. Higher ethanol content was detected in dogwood and redbud subjected to flood stress compared to flooded red maples and tree species assigned to drought and sufficient water. This understanding can help growers and landscapers in making informed management decisions.