Epidemiology and management of wheat scab in China
1997
Wang, Y.Z. (Institute of Plant Protection, Nanjing, PR (China). Jiangsu Academy of Agricultural Science)
Wheat scab or fusarium head blight (FHB) of wheat, caused by Gibberella zeae (Schw) Petch, can be found in more than 2O provinces of China and affects more than 6.7 million ha. The most affected areas are in the provinces along the Yangtze River, especially in Jiangsu province where the disease has a high epidemic frequency and causes severe yield losses. Eighteen species of Fusarium have been identified from 21 provinces or areas. Among them, F. graminearum predominated, representing 94.5 percent of the samples. The differences in pathogenicity among species of Fusarium and among isolates of F. graminearum were significant. Among 18 species of Fusarium, F. graminearum was most virulent and was divided into three pathogenic types: strongly, moderately, and weakly pathogenic. The number of strongly pathogenic isolates from the regions of high epidemic frequency was much greater than that from regions of low epidemic frequency. To date, no pathogenic specificity of F. graminearum isolates have been found. The wheat scab pathogen multiplies on the residues of many plants. The main infection sources are perithecia and ascospores produced on paddy stubble. Test results have demonstrated that the pathogen can survive through winter and summer in soil, diseased seeds, and in the straw of wheat, rice and maize; however, it was observed that it mainly overwinters and oversummers in the soil. In general, the pathogen can only be saprophytic on rice stubble in rice-wheat rotation areas and on maize stems in dry planting areas. Growth and decline in the number of airborne spores of the pathogen correlated closely with rainfall. Number of spores usually peaked on days of rain, and 1-2 days after rain. Ascospores and conidia had the same pathogenicity. Disease developed most rapidly at 25 centigrade and high moisture persisting for more than 36 hours.
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