Two new pathogens, Guignardia korthalsellae and Rosenscheldiella korthalsellae, are described from New Zealand's pygmy mistletoes (Korthalsella, Viscaceae). Both form ascomata on living phylloclades with minimal disruption of the tissue. Fungal hyphae within the phylloclade are primarily intercellular. Guignardia korthalsellae disrupts a limited number of epidermal cells immediately around the erumpent ascoma, while the ascomata of Rosenscheldiella korthalsellae develop externally on small patches of stromatic tissue that form above stomatal cavities. Rosenscheldiella is applied in a purely morphological sense. LSU sequences show that R. korthalsellae as well as another New Zealand species, Rosenscheldiella brachyglottidis, are members of the Mycosphaerellaceae sensu stricto. Genetically, Rosenscheldiella, in the sense we are using it, is polyphyletic; LSU and ITS sequences place the two New Zealand species in different clades within the Mycosphaerellaceae. Rosenscheldiella is retained for these fungi until generic relationships within the family are resolved. Whether or not the type species of Rosenscheldiella, R. styracis, is also a member of the Mycosphaerellaceae is not known, but it has a similar morphology and relationship to its host as the two New Zealand species.

Taxonomic novelties:Guignardia korthalsellae A. Sultan, P.R. Johnst., D.C. Park & A.W. Robertson, sp. nov.; Rosenscheldiella korthalsellaeA. Sultan, P.R. Johnst., D.C. Park & A.W. Robertson, sp. nov.

从新西兰的侏儒槲寄生（Korthalsella，Viscaceae）中描述了两种新的病原体，Guignardia korthalsellae和Rosenscheldiella korthalsellae。两者都在活的叶状体上形成子囊，对组织的破坏最小。叶分枝内的真菌菌丝主要是细胞间的。Guignardia korthalsellae破坏紧邻 erumpent 子囊周围的有限数量的表皮细胞，而Rosenscheldiella korthalsellae 的子囊在气孔上方形成的小块基质组织上在外部发育。Rosenscheldiella是在纯粹的形态学意义上应用的。LSU 序列显示R. kothalsellae以及另一种新西兰物种Rosenscheldiella brachyglottidis都是严格的Mycosphaerellaceae sensu stricto 的成员。从遗传上讲，Rosenscheldiella，就我们所使用的意义而言，是多系的。LSU 和 ITS 序列将这两个新西兰物种置于Mycosphaerellaceae内的不同进化枝中。Rosenscheldiella保留用于这些真菌，直到解决家庭内的一般关系。Rosenscheldiella 的模式种R. styracis是否也是Mycosphaerellaceae的成员尚不清楚，但它与这两种新西兰物种具有相似的形态和与其宿主的关系。

分类新奇：Guignardia korthalsellae A. Sultan, PR Johnst ., DC Park & AW Robertson, sp. 十一月；Rosenscheldiella korthalsellae A. Sultan, PR Johnst ., DC Park & AW Robertson, sp. 十一月