大豆褐纹病发生规律及预测预报

STUDIES ON THE EPIDEMIC REGULARITY AND PREDICTING METHOD OF THE SOYBEAN BROWN SPOT (SEPTORIA GLYCINES)

大豆褐纹病(Septoria glycines Hemmi)的初侵染来源以越冬病残体内分生孢子器产生的孢子为主,以种子带菌为辅。在适温条件下,保湿24h以上病菌即可完成侵染。在30℃条件下,潜育期为4d。大豆出苗后,当气象日(日平均气温稳定通过15℃,日最低温度>10℃,日平均相对湿度>80％或有0.1mm以上降雨的日期)连续出现3d,7～10d后田间始见病斑,温度越高病斑出现日期越早。大豆生长发育前期和后期病情增长速率较快,而大豆生长发育中期病情增长速率较慢。病害的发生程度与6月20日至8月31日的降雨量、降雨日数、日平均相对湿度、日平均相对湿度≥85％的日数和阈值温湿度日(日平均温度>20℃,日平均相对湿度<85％或无雨的日数)呈显著相关。建立了Fuzzy函数预测模型。

The primary infection source of Septoria glycines was mainly from conidium within pycni-dium survived in plant residues infected in previous year. The seed-transmitted pathogen was only the supplement. The infection of S. glycines may be limited by the duration of leaf water-keeping time. It was demanded for 24 h at least. The latent period was four days under the temperature of 30℃ . When the averaged day temperature was ≥ 15℃ for three continuous days, the relative humidity > 80% or rainfall > 0.1 mm, the soybean leafs were infected during the period of 25th May to 15th June. The disease developed more rapidly at the early and the late stage of soybean growth while the development was slower at middle stage. The severity of the disease was significantly related to the weather factors rain-days, precipitation, the relative humidity, the temperature ( > 20℃ ) , and the days with the averaged relative humidity < 85% or without rainfalls. A mathematical model as established to forecast accurately the degrees of infected soybean leaves using Fuzzy function.