Audley Jackson, Klingeman William E, Mayfield Albert, Myers Scott, Taylor Adam
Department of Forestry Wildlife and Fisheries, University of Tennessee, 2506 Jacob Drive, Knoxville, TN 37996.
Plant Sciences Department, University of Tennessee, 2431 Joe Johnson Drive, Knoxville, TN 37996.
J Insect Sci. 2017 May 1;17(3). doi: 10.1093/jisesa/iex046.
Thousand cankers disease, caused by the invasive bark beetle Pityophthorus juglandis Blackman and an associated fungal pathogen Geosmithia morbida M.Kolařík, E. Freeland, C. Utley, N. Tisserat, currently threatens the health of eastern black walnut (Juglans nigra L.) in North America. Both the beetle and pathogen have expanded beyond their native range via transport of infested walnut wood. Geosmithia morbida can develop in seedlings following inoculation, but the ability of P. juglandis to colonize young, small diameter trees has not been investigated. This study assessed the beetle's colonization behavior on J. nigra nursery trees. Beetles were caged directly onto the stems of walnut seedlings from five nursery sources representing a range of basal stem diameter classes. Seedlings were also exposed to P. juglandis in a limited choice, field-based experiment comparing pheromone-baited and unbaited stems. When beetles were caged directly onto stems, they probed and attempted to colonize seedlings across the range of diameters and across sources tested, including stems as small as 0.5 cm in diameter. In the field experiment, beetles only attempted to colonize seedlings that were baited with a pheromone lure and appeared to prefer (though not statistically significant) the larger diameter trees. Despite several successful penetrations into the phloem, there was no evidence of successful progeny development within the young trees in either experiment. Further investigation is recommended to better elucidate the risk nursery stock poses as a pathway for thousand cankers disease causal organisms.
千溃疡病由入侵性树皮甲虫胡桃小蠹（Pityophthorus juglandis Blackman）和一种相关的真菌病原体——黑核桃嗜木菌（Geosmithia morbida M.Kolařík、E. Freeland、C. Utley、N. Tisserat）引起，目前正威胁着北美东部黑核桃（Juglans nigra L.）的健康。甲虫和病原体都通过受侵染的核桃木运输扩散到了它们的原生范围之外。黑核桃嗜木菌在接种后可在幼苗中生长，但胡桃小蠹在幼龄、小径级树木上定殖的能力尚未得到研究。本研究评估了该甲虫在黑核桃苗木上的定殖行为。将甲虫直接关在来自五个苗圃来源的核桃幼苗茎上，这些幼苗代表了一系列不同的基部茎直径等级。在一项基于田间的有限选择实验中，还让幼苗接触胡桃小蠹，该实验比较了用性信息素诱饵诱捕和未诱捕的茎。当将甲虫直接关在茎上时，它们会探测并试图在测试的不同直径范围和不同来源的幼苗上定殖，包括直径小至0.5厘米的茎。在田间实验中，甲虫只试图在用性信息素诱饵诱捕的幼苗上定殖，并且似乎更喜欢（尽管无统计学意义）直径较大的树木。尽管有几次成功穿透到韧皮部，但在两个实验中均没有证据表明幼树内有成功的后代发育。建议进一步调查，以更好地阐明苗木作为千溃疡病致病生物传播途径所带来的风险。
