Since 2006 there has been a decline in Colorado blue spruce (CBS; Picea pungens) planted as landscape trees and for Christmas tree production throughout the Lower Peninsula of Michigan. This decline is characterized by a slow loss of needles in the lower portion of the tree starting at branch tips, followed by entire branch dieback, which progresses upward over several years. This dieback has been linked to shallow branch cankers visible in the phloem when the bark layer is removed. Isolates in the fungal genus Diaporthe have been consistently isolated from lesion margins on symptomatic branches. Before the initial reports of declining CBS in landscape and Christmas trees, Diaporthe was known only as a nursery disease of CBS. To determine the species of Diaporthe linked to the decline of CBS in Michigan, seven gene regions were sequenced from a collection of Diaporthe isolates collected in 2011 through 2018 from CBS and other coniferous hosts. Subsequent phylogenetic analyses indicated that Diaporthe eres and a novel Diaporthe clade were present on symptomatic CBS in Michigan. The new species D. brevicancria nov. is described, and Koch’s postulates were confirmed for D. brevicancria nov. and D. eres. D. brevicancria nov. produced the largest cankers in greenhouse pathogenicity trials, and dual inoculations of D. brevicancria nov. and D. eres produced intermediate cankers.

自2006年以来，整个密歇根州下半岛种植的科罗拉多州蓝云杉（CBS; Picea pungens）的景观树和圣诞树的产量一直在下降。这种下降的特征是从树枝顶端开始，树下部的针叶缓慢丢失，然后整个树枝都死掉了，这种情况持续了数年之久。当树皮层被去除时，这种枯萎与韧皮部中可见的浅分支溃疡有关。真菌属Diaporthe的分离株一直与有症状分支的病灶边缘分离。在有关景观和圣诞树中CBS下降的最初报道之前，Diaporthe仅被称为CBS的苗圃病。确定种类Diaporthe与密歇根州CBS的下降有关，从2011年至2018年从CBS和其他针叶宿主中收集的Diaporthe分离株的集合中，对七个基因区域进行了测序。随后的系统发育分析表明，密歇根州有症状的CBS上存在Diaporthe eres和一个新颖的Diaporthe进化枝。新种D. brevicancria nov。进行了描述，并确认了D. brevicancria nov的Koch假设。和D. eres。D. brevicancria nov。在温室致病性试验中产生了最大的溃疡病，并且对D. brevicancria nov进行了两次接种。和D. eres 生产的中间溃疡病。