Gnomonia Leptostyla (Fr.) Ces. et de Not. causer of walnut anthracnose in the east part of the Republic of Macedonia

Abstract

The anthracnose is one of the most destructive diseases of walnut (Juglans regia L.) worldwide. The causal agent is an ascomycetous fungus (Gnomonia leptostyla (Fr.) Ces. et de Not.) (anamorph Marssonina juglandis (Lib.) Magn.). In the last years symptoms of the disease were observed with increasing frequency in Macedonia. The leaves, nuts, and occasionally shoots were affected. Leaf spots were dark brown, more or less circular and often coalesced forming larger dead areas. Black minute fruiting bodies called acervuli developed more abundantly on the under side than on the upper side of leaflets and produced a lot of conidia. Conidia were colorless, usually crescent-shaped, rounded at one end and tapered at the other and divided by septa into two approximately equal cells. The severe attack caused defoliation in infected trees. The spots on the walnut husks were sunken and smaller than on the leaves. Early infection could lead to fruit deformation and they prematurely dropped. In the spring the perfect or sexual fungus G. leptostyla was found on fallen overwintered walnut leaves. Perithecia with long necks discharged numerous asci with ascospores serving as primary inoculum. Ascospores were hyaline, fusiform and bicelullar. Our results showed that both stages were involved in the disease under climatic condition of Macedonia. Collecting and burning or plowing the infected plant materials would aid in the control of this disease.