Spruce Protection against Ips typographus with Anti-Attractant Blend of Tree-Based Semiochemicals: From Small Experimental Plots to Stand Scales

Abstract

Tree-killing bark beetles require rapid management, such as anti-attractants, to stop the enlargement of attack hot-spots. We tested two newer anti-attractant blends, both without verbenone and one with the addition of trans-4-thujanol, in traps against standard pheromone baits for inhibition of catch. Both blends provided effective catch reduction (>95%). We also tested these anti-attractant blends in tree protection experiments for two years. We had experimental plots with a center of an anti-attractant protected tree zone, with no traditional control area, but we followed tree kills in 10 m wide concentric rings to 100 m. In 2020, we had 12 plots, and 9 plots in 2021. Monitoring by low-strength pheromone traps followed beetle flight averaging 300/trap during the shorter period, August 2020, and 5000/trap during the longer period, May to August 2021. The blends of anti-attractants were 100% effective in avoiding tree mortality in both treated trees and their surroundings. There were no bark beetle attacks on any treated trees, and there was zero tree mortality up to 19 m in 2020, and up to 30 m in 2021, thus full protection to circa 20 m. The density of killed trees then increased from close to zero, over 20 to 50 m, reaching a level of ca 30 (trees/ha) then declined. The spatial pattern of tree mortality on our experimental plots was highly heterogeneous and individual 10m-ring data points on tree kill density could not be statistically separated. In contrast, a non-linear regression model showed a continuous increase of attacks over the distance from the center to a peak ca 60m, followed by a decline. This model agrees partly with the only similar study in the literature, but importantly, it does not give a peak of kill density at distances between the first and second rings close to treatment zones. Such patterns of close-quarter kills have been observed as a “switching” of attack in this and other scolytid systems manipulated by anti-attractants, but not in the present study, likely due to the elimination of verbenone from our blends.

Mitigating Norway spruce mortality through the combined use of an anti-attractant for Ips typographus and an attractant for Thanasimus formicarius

“…However, in traps treated with both attractants (I. typographus pheromone and T. formicarius attractant) and anti-attractant, no I. typographus were caught, while the highest numbers of T. formicarius were observed (Figure 2). The absence of I. typographus catches in the combined treatment traps may be attributed to the strong repellent effects of tree-based antiattractants comprising the anti-attractant dispenser (Jakuš et al, 2024). The deterrent effect might have outweighed the luring effect of the I. typographus attractant, despite the latter presumably being enhanced by the presence of Ie, Id, and MB-compounds constituting the T. formicarius attractant dispenser.…”

“…The second attractant dispenser used in our study was ThanasiWit R (Witasek PflanzenSchutz GmbH, Feldkirchen in Kärnten, Austria), that was designed for T. formicarius, which contains 2-methyl-3-buten-2-ol, ipsenol, ipsdienol, and phenylethanol. As an anti-attractant for I. typographus, a pouch dispenser containing green leaf and non-host volatiles 1-hexanol, 1-octen-3-ol, 3octanol, eucalyptol, trans-thujanol, and trans-conophthorin was produced by Synergy Semiochemicals Corp. (British Columbia, Canada), in accordance with the formula published in Jakuš et al (2024).…”

“…Recently, oxygenated monoterpenes derived from host trees, such as trans-thujan-4-ol, have been reported to possess anti-attractant properties (Kalinová et al, 2014;Blažytė-Čereškienė et al, 2016;Schiebe et al, 2019;Jirošová et al, 2022). These compounds have been incorporated into dispensers for tree protection, yielding various degrees of success (Jakuš et al, 2003(Jakuš et al, , 2022(Jakuš et al, , 2024Schiebe et al, 2011;Deganutti et al, 2023). A novel dispenser, developed by Jakuš et al (2024) and devoid of beetle-derived compounds, has exhibited promising efficiency.…”

“…These compounds have been incorporated into dispensers for tree protection, yielding various degrees of success (Jakuš et al, 2003(Jakuš et al, , 2022(Jakuš et al, , 2024Schiebe et al, 2011;Deganutti et al, 2023). A novel dispenser, developed by Jakuš et al (2024) and devoid of beetle-derived compounds, has exhibited promising efficiency. However, anti-attractants are still not widely used in practical forest protection measures due to their limited effectiveness and relatively high costs in tree protection.…”

“…Additionally, the paper examines the feasibility of using a combined treatment, that consists of the attractant for T. formicarius and anti-attractant for I. typographus, to protect trees against I. typographus attacks. We also aim to develop a basis for further reinforcing the effectiveness of our tree protection method based on the use of anti-attractants (Jakuš et al, 2024). We anticipated observing the highest I. typographus catches in traps baited with the pheromone of I. typographus and attractant developed for T. formicarius.…”