Effects of Application Rate of Biological Fungicide ZY-9-13 on Occurrence of Tobacco Black Shank Disease

In order to investigate the control effect of biological fungicide ZY-9-13 against Phytophthora parasitica var．nicotianae, its population density in soil, the disease incidence and index of tobacco plants and control effect were determined by field experiments at ZY-9-13 application rates of 0, 2.25, 4.50, 6.75 kg/hm². The results showed that with the increase of application rate, the population density of Phytophthora parasitica var．nicotianae in soil, the disease incidence and index decreased, the control effect increased. The control effect peaked at ZY-9-13 application rate of 4.50 kg/hm².