Het parasitaire karakter van Septotinia populiperda Waterman & Cash

Summary Mature apothecia ofSeptotinia populiperda Waterman andCash are formed in spring and early summer on leaves shed the previous autumn. The ascospores ofS. populiperda produce an infection in the form of leafblotches only when an injury of the leaf is present.P. candicans Ait. is more susceptible to the parasite thanP. marilandica Bosc. andP. brabantica Houtz. Leafblotches are produced in equal numbers when the ascospores are sprayed with an atomizer upon the upper or the lower leafsurface. The germination of the ascospores is inhibited in vitro at a concentration of 7 to 8 mg copper per liter, when copper is used as Bordeaux mixture, or as coppersulfate (CuSO₄5H₂O).