三裂叶豚草锈病发生和流行规律的研究

通过田间调查与定点系统观察，结合沈阳地区的气象条件，对三裂叶豚草锈病在沈阳地区的发生和流行规律进行了研究。结果表明：三裂叶豚草锈病属于喜高温、高湿型病害；该病于6月初在沈阳地区开始发病，可持续至9月，以7～8月发病最重。人工接种试验结果表明：在30℃和相对湿度96．9％条件下接种锈菌冬孢子，4d后三裂叶豚草即可发病；冷冻保藏（-20℃）可打破冬孢子休眠，在沈阳地区冬孢子是第二年锈病发生的初侵染菌源。苍耳柄锈菌三裂叶豚草专化型对三裂叶豚草表现出了显著的致病性、致死性及专一性，证明是防治三裂叶豚草的理想生防菌。

Incidence and Epidemics of Giant Ragweed Rust (Puccina xanthii f. sp. ambrosiae-trifidae)

The incidence and epidemic of giant ragweed rust （ Puccina xanthii f. sp. ambrosiae-trifidae） in Shenyang area were investigated through field investigation and site observation in plots. The results indicate that the rust was significantly favored by high temperature and high humidity. It occurred in early June and lasted until September in Shenyang area. It was most serious in July and August. The artificial inoculation of giant ragweed plants by teliospores produced symptom on leaves after 4 days at 30 ℃ and relative humidity 96.7 %. The freezing treatment （ - 20 ℃ ） of teliospores could break their dormancy and promote their germination. The teliospores were found to be the inoculum source for the disease in Shenyang area. It is determined that the rust fungus is an expected bioeontrol agent for giant ragweeds due to its obligate parasitism and strong pathogenicity.