Studies on Pathogenic Fungus of Canker of Black Locust

Serious black locust canker occurs in Shandong coastal areas. Pathogenetic fungi are identified as Fusarium oxysporum and Fusarium solani. Microconidia of the first aggregate a capitulum and develop on the single ampuliform conidiophore. Microconidium are elliptic and botuliform in shape,7.6～15.4 μm× 2.5～3.8 μm and macroconidium are falciform and cambiform with 3～5 septum,28.2～38.4 μm×4.6～5.1 μm. The diameters of chlamydospore are 8.9～12.8 μm. For the second,microconidia grow on the elongated conidiophore and the shapes are broad ovate and elliptic,5.1～10.2 μm ×2.5～4.8 μm. Conidiophore are 30～80 μm in length. Macroconidium is blunt at both ends with 3～5 septum,20.1～33.3 μm× 2.6～5.4 μm. Chlamydospore are 7.7～10.2 μm in diameters. The appropriate temperature for the colony growth is 25～30 ℃ with 28 ℃ as the optimum. The range of pH is 5～9 and micro acid or neutrality is the most favourable. The best origin of carbon is sucrose or glucose,and peptone is best nitrogen source. F. oxysporum has stronger pathogenicity and is the main pathomycete of black locust canker.