Inhibition of sporulation of Phomopsis viticola Sacc., cause of dead arm disease of vines, by fosetyl-Al under field conditions

Abstract

Several plots of vines, naturally infected with Phomopsis viticola Sacc., were given a single application of fosetyl-Al + folpet at various growth stages starting from stage A in January. At varying intervals after treatment, the spores released from the pycnidia were counted on sections of vine canes in the laboratory. The effectiveness of treatments was also assessed in the field. An inhibition of sporulation of up to 95% occurred, lasting until 2 months after treatment; however, this inhibition, probably caused by fosetyl-Al, can only partly explain the efficacy obtained in the field with these treatments. The fact that the antisporulation activity of fosetyl-Al on P. viticola occurs during the period of vegetative shutdown appears to exclude the involvement of the plant in the mode of action of the fungicide in this case.