[Factors influencing pathogenicity of Collectotrichum gloeosporioides f.sp. veronicae to Veronica persica].
The effects of the characters of the fungus, the growing period of plants and environmental factors on the pathogenicity of Colletotrichum gloeosporioides f.sp. veronicae infecting Veronica persica were studied in pot experiments. The results showed that 1.08 x 10(8) spores.ml-1 suspension could kill the seedlings with two cotyledons within one week and cause old plants serious disease. 1 x 10(8) spores.ml-1 was optimal concentration and 1 or 2 weeks old was the best age of the spores for killing birdseye speedwell. The optimal temperature was 15-25 degrees C for the disease development. More than two days' dew exposure was required to kill the weed. However, the disease was also developed better when corn or soybean flour was added or the darkness period during dew exposure was prolonged.