LAUSR

Salix babylonica is an important landscape tree in China and has been widely planted. In this study, the pathogenicity of Septotinia populiperda causing leaf blotch of Sa. babylonica to four willows (Sa. chaeomoloides, Sa. matsudana, Sa. matsudana f. tortuosa, and Sa. suchowensis) and Populus tomentosa (Chinese white poplar) was determined. Its sexual stage and biological characters were studied. Leaves from four willows and P. tomentosa were inoculated with mycelial plugs. Typical leaf blotches with sporodochia were produced on all inoculated leaves. Among the isolates studied, some developed conidia, but sclerotia were rare. The sclerotia developed apothecia after induction at 4°C for three months in an incubator and two more months outdoors from January to March. The biological characteristics of S. populiperda showed that mycelium grew better on complete medium (CM) than on potato dextrose agar (PDA), Czapek's agar (CZA), and minimal medium (MM). For mycelial growth, the optimal carbon source was dextrose, and the optimal nitrogen source was yeast powder. Conidia germination rate was 59.4% at 24 hrs. The conidia germinated best in a 4% willow leaf extraction. The optimal temperature for conidia germination was 25°C, and the optimal pH was 4.