USDA Forest Service, Pacific Southwest Research Station, Davis, CA, 95618, USA.
Department of Plant Pathology, University of California, Davis, CA, 95616, USA.
J Chem Ecol. 2020 Dec;46(11-12):1047-1058. doi: 10.1007/s10886-020-01228-9. Epub 2020 Oct 27.
Thousand cankers disease (TCD), is an invasive insect-disease complex caused by the walnut twig beetle, Pityophthorus juglandis, and fungal pathogen, Geosmithia morbida. Semiochemical interruption is a viable option for protecting walnut trees from P. juglandis attack. The goal of this study was to test beetle responses to potential repellent compounds. The results of five, flight-intercept assays are reported. Assays 1-3 tested four compounds at variable release rates: (S)-(-)-verbenone, (R)-(+)-verbenone, racemic chalcogran, and racemic trans-conophthorin. Trapping results indicated that the highest release rate tested for each compound was the most effective in reducing the number of beetles caught. (S)-(-)-Verbenone was the least effective, reducing P. juglandis trap catches by 66%. (R)-(+)-Verbenone reduced the number of P. juglandis by 84%. Neither enantiomer of verbenone performed as well as chalcogran or trans-conophthorin, which both reduced the number of beetles caught by ca. 98%. Following individual assays, the most effective compounds were tested in subtractive-combination assays. Combinations of high release rates for (R)-(+)-verbenone, trans-conophthorin, and two stereoisomers of limonene (tested in a previous study) were tested in two assays. The subtractive-combination assays were inconclusive in that trap catches were similar across all treatments. All combination treatments were highly effective, achieving approximately 99% reduction in the number of beetles caught. Based on the trapping results, commercial availability, and cost of the semiochemicals tested, we conclude that a combination of (R)-(+)-limonene, trans-conophthorin, and (R)-(+)-verbenone constitutes an effective tool for reducing P. juglandis trap catches.
核桃溃疡病（TCD）是由胡桃枝小蠹和真菌病原体 Geosmithia morbida 引起的一种侵袭性昆虫病害。半化学物质干扰是保护核桃树免受胡桃枝小蠹攻击的可行选择。本研究的目的是测试甲虫对潜在驱虫化合物的反应。报告了五项飞行截获测定的结果。测定 1-3 测试了四种化合物在不同释放率下的反应：(S)-(-)-马鞭草烯酮、(R)-(+)-马鞭草烯酮、外消旋查尔酮和外消旋反式-康普托林。诱捕结果表明，每种化合物测试的最高释放率最有效地减少了捕获的甲虫数量。(S)-(-)-马鞭草烯酮的效果最差，减少了 66%的胡桃枝小蠹诱捕量。(R)-(+)-马鞭草烯酮减少了 84%的胡桃枝小蠹数量。马鞭草烯酮的两种对映体都不如查尔酮或反式-康普托林有效，这两种化合物都减少了约 98%的甲虫捕获量。在单独测定后，最有效的化合物在减法组合测定中进行了测试。在两项测定中，测试了(R)-(+)-马鞭草烯酮、反式-康普托林和两种柠檬烯立体异构体（在先前的研究中测试过）的高释放率组合。减法组合测定的结果并不明确，因为所有处理的诱捕量都相似。所有组合处理都非常有效，实现了约 99%的甲虫捕获量减少。基于诱捕结果、半化学物质的商业可用性和成本，我们得出结论，(R)-(+)-柠檬烯、反式-康普托林和(R)-(+)-马鞭草烯酮的组合构成了减少胡桃枝小蠹诱捕量的有效工具。
