The «Hoja de Malvón» Grape Disease in Argentina

Abstract

“Hoja de malvón” is the common name of a disease that has been observed in grapevines of Argentina since the beginning of the century. This paper reports the status of this disease in this country. The disease starts appearing in one of the plant arms. Leaves are smaller than normal, chlorotic and with the edges rolled downwards, the canes and current-year shoots show reduced growth and the clusters are smaller and sparser with berries of non uniform-size. In a cross sectional cut of the trunk two types of necrosis could be observed: a yellowish necrosis of soft consistency, or decay, in a central or sectorial position, surrounded by a black line and a brownish area; and a sectorial light brown necrosis of hard consistency, surrounded by a brown zone. Sometime, black spots are observed at the edge of the damaged areas. Isolations from trunk tissues of different cultivars of grafted and nongrafted plants, 3- to 30-year-old, were done in malt extract agar. Phellinus sp., Botryodiplodia sp. and Phaeoacremonium spp. (P. aleophilum, P. chlamydosporum and P. parasiticum) were isolated. Up to now, in vitro pathogenicity tests were conducted only with Phellinus sp., Botryodiplodia sp. and P. chlamydosporum, which were able to cause the decline and death of young plants. Research attempting to quantify the effects, and to study the factors influencing the appearance of the disease, is also being conducted. Only preventive practices are recommended for its control.