苏北杨树黑斑型溃疡病的研究

Study on black blotch canker of poplars in north Jiangsu

在苏北杨树上新近发生一种不规则黑斑型溃疡病，调查发现该病害是造成苏北新造林地杨树大量死亡的主要原因。通过对病原的分离、接种和再分离，发现杨树黑斑型溃疡病主要由2种病原菌引起：一种分生孢子单孢，纺锤形，基部平截，孢子大小为（17．5～27．5）μm×（4．0～5．5）μm，平均大小23．5μm×4．5μm，分生孢子梗透明，在近基部分枝，大小为21μm×2．0μm，经鉴定为七叶树壳梭孢（Fusicoccum aesculi）；另一种产生甲型和乙型两种孢子，甲型孢子单孢椭圆形，乙型孢子线形，一端弯曲呈钩状，鉴定为拟茎点霉（Phomopsis macrospora）。两种病原菌单独接种均可使杨树枝条产生小的黑斑，混合接种可加重病害的发生，形成大型不规则黑斑。

The black blotch canker of poplars which is a new kind of poplar canker disease occurred in north Jiangsu recently. Research on this disease indicated that it was the main death reason of new planted poplars in this area. According to isolation and identification results, this disease could be caused by Fusicoccum aesculi and Phomopsis macrospora. For F. aesculi, the conidium is single, fusiform and the base truncation. Its size is between （17.5- 27.5 ） μm×（ 4. 0-5.5 ） μm and the average size is 23.5 μm × 4. 5 μm. The conidiospores are transparent, which are branching near the bases. Its average size is 21 μm × 2.0 μm for P. macrospora, two shapes of conidia are found, i.e. fusiform and linear with curved top. Two pathogens which inoculated the stem of the poplars respectively, caused poplar to have little black spots. The mixed inoculation with two pathogens could aggravate the diseases by forming big black blotch.