Occurrence Dynamics of Tobacco Target Spot and Its Relationship with Environmental Factors in Hubei Province

In order to forecast reasonably and prevent precisely the occurrence of tobacco target spot (TTS) in Hubei Province, the epidemic dynamics were confirmed, the relationship between the occurrence of TTS and contents of Rhizoctonia solani in soil, meteorological conditions were revealed by using system investigation and statistical analysis in this study. Results showed that the disease stages of TTS in Hubei Province behaved as the followings: Disease onset (35-40 d after transplantation) - Disease expansion (40-60 d after transplantation) - Disease rapid spread (60-105 d after transplantation). The logistic model well reflected the epidemic dynamics of TTS, thus the occurrence of this disease could be predicted by using this model. The contents of R. solani at 10 cm tillage depth was higher than that of other tillage depths. The contents of R. solani in soil exhibited a trend of continuous increase during the field growth period of tobacco, and significantly positively correlated with the disease index of TTS. Temperature and rainfall were the main meteorological factors affecting the occurrence and prevalence of TTS. When temperature in field exceeded 23 ℃, TTS spread rapidly. At each disease stage, the severity of disease depends on the total rainfall. This study highlights the occurrence dynamics and influenced factors of TTS in Hubei Province, and provides a theoretical foundation for the prediction, forecast, reasonable prevention and control of TTS.