Acibenzolar-S-methyl induces resistance against ambrosia beetle attacks in dogwoods exposed to simulated flood stress

Authors: PARAJULI, MADHAV - Tennessee State University; OKSEL, CANSU - Tennessee State University; NEUPANE, KRISHNA - Tennessee State University; Ranger, Christopher; OLIVER, JASON - Tennessee State University; ADDESSO, KARLA - Tennessee State University; BAYSAL-GUREL, FULYA - Tennessee State University

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2023
Publication Date: 8/1/2023
Citation: Parajuli, M., Oksel, C., Neupane, K., Ranger, C.M., Oliver, J., Addesso, K., Baysal-Gurel, F. 2023. Acibenzolar-S-methyl induces resistance against ambrosia beetle attacks in dogwoods exposed to simulated flood stress. Journal of Insect Science. 23(4):12; 1-8. https://doi.org/10.1093/jisesa/iead068.
DOI: https://doi.org/10.1093/jisesa/iead068

Interpretive Summary: Ambrosia beetles are important wood-boring pests of trees weakened by stressors. Maximizing tree health is an important tactic for minimizing the risk of infestations by ambroisa beetles. A plant defense elicitor, acibenzolar-S-methyl (ASM), was tested for inhibiting ambrosia beetle tunneling into flood-stressed dogwoods (Cornus florida L.). Container-grown dogwoods were treated with ASM or untreated and then flood stressed to make the trees attractive to ambrosia beetles. Ambrosia beetle tunnleing into the experimental trees was then monitored over time. Trees were also dissected to count the number of offspring as a measure of colonization success. The highest number of ambrosia beetle tunnels were recorded from trees that were not treated with the defense elicitor. Pre-treatment of the stressed trees with ASM reduced ambrosia beetle tunneling and the presence of eggs, larvae, and adults. These results provide the first evidence that pre-treatment with ASM can be used to aid in protecting vulnerable trees from infestation by ambrosia beetles.

Technical Abstract: Ambrosia beetles (Xylosandrus spp.) are important wood-boring pests of trees weakened by abiotic and biotic stressors. Acibenzolar-S-methyl (ASM), a plant defense elicitor, was tested for inhibiting ambrosia beetle tunneling (i.e., attacks) into flood-stressed dogwoods (Cornus florida L.). Container-grown dogwoods were treated with ASM substrate drench + flooding, ASM foliar spray + flooding, ASM drench + no flooding, ASM foliar + no flooding, no ASM + flooding, or no ASM + no flooding at 3-d before flood stress in a completely randomized design under field conditions. Trees were flooded for 14 d and then drained and watered as needed. Attacks were counted every 2-d for 28 d. Plant tissue samples were collected at 7- and 14-d after flooding to determine ethanol content using solid-phase microextraction–gas chromatography–mass spectrometry (SPME-GC-MS). Trees were dissected to determine successful gallery formation and depth, fungal colonization, and presence of eggs, larvae, and adults. The highest number of ambrosia beetle attacks were recorded from plants exposed to no ASM + flooding recorded, but attacks were reduced in ASM treated trees (drench or foliar) + flooding. Trees treated with drenches had fewer attacks than foliar sprays. Plants assigned to no flood had the fewest beetle attacks. Moreover, ASM reduced ambrosia beetle gallery formation and depth, fungal colonization, and presence of eggs, larvae, and adults. All flooded trees produced ethanol. In conclusion, ASM induced a plant defense response to ambrosia beetle tunneling in dogwoods under flood stress conditions.