Location: Application Technology ResearchTitle: Colonization of trees by ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) is influenced by duration of flood stress
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2021
Publication Date: 3/2/2021
Citation: Reding, M.E., Ranger, C.M., Schultz, P.B. 2021. Colonization of trees by ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) is influenced by duration of flood stress. Journal of Economic Entomology. 114(2):839-847. https://doi.org/10.1093/jee/toab021.
Interpretive Summary: Damaging ambrosia beetles (Xylosandrus germanus and Xylosandrus crassiusculus) are attracted to and preferentially attack stressed trees emitting ethanol. Ambrosia beetles bore into the xylem of trees excavating tunnels (galleries). Stressors such as flooding induce trees to produce and emit ethanol. Flooding is one of the most common ethanol-inducing stressors occurring in tree crops. In previous research, ambrosia beetles attacked flood stressed trees within 2 days of initiating flood conditions and offspring were present in galleries (successful colonization) after 15 days of flooding. However, whether ambrosia beetles can successfully colonize trees after short-term flood events (more common than long-term) is unknown. The current research examined colonization success (offspring produced) by X. germanus and X. crassiusculus on trees flooded for various periods of time (days). Successful colonization was more likely as the number of days flooded increased. Trees flooded for only three days were readily attacked, but the attacking beetles were often dead or missing and offspring were rarely found. Furthermore, attacked trees flooded only three days were able to survive through the following spring and blossom. This research indicates growers may not have to cull trees attacked during short-term flood events.
Technical Abstract: The ambrosia beetles Xylosandrus germanus (Blandford) and Xylosandrus crassiusculus (Motschulsky) attack flood stressed trees emitting ethanol. However, duration of flooding needed to facilitate colonization by ambrosia beetles is unknown. This relationship was examined by flooding trees for various time-periods and evaluating colonization success. In one experiment, 20 dogwood (Cornus florida L.) trees were attacked by X. germanus during a 3-day flood treatment. Ten trees dissected that season, had no offspring present in tunnels. The remaining attacked trees appeared healthy and bloomed the following spring. In another experiment, dogwood trees were flooded 3 or 7 days, with more X. germanus attacks and a greater incidence of offspring present in 7-day trees; greater incidence of superficial (short unbranched) and healing (callus tissue in entrance) tunnels occurred in 3-day trees. Four experiments (3 in OH and 1 in VA) had flood treatments of 0 (non-flooded), 3, 5, 7, and 10 days. Ohio experiments on apple (golden delicious), dogwood, and redbud (Cercis canadensis L.), had no attacks on non-flooded trees. The Virginia experiment on redbud, had 3 non-flooded trees attacked. Total attacks, X. germanus attacks, and indicators of colonization success such as incidence of offspring or live foundresses tended to increase as flood duration increased. While indicators of unsuccessful colonization such as superficial tunnels and healing decreased as flood duration increased. These results suggest tree crops may recover from attacks during short flood events, and may not require culling.