用2个感病的玉米材料接种玉米丝黑穗病菌，苗期调查侵染率，开花期调查发病率，结果表明侵染率显著高于发病率；在开花期提取未发病植株茎髓组织DNA进行PCR检测，结果检测到玉米丝黑穗病菌DNA的存在。因此，通常情况下玉米丝黑穗病侵染率大于发病率。

By choosing two disease varieties of corn and inoculating spore of maize head smut when planting, and investigating infection rate at seedling stage and disease incidence at blooming stage, we got the result that the infection rate was much higher than the rate of disease. At the same time, we inspected the DNA of healthy plant at blooming stage by PCR, and found the DNA of maize head smut germ. We could draw a conclusion that the infection rate was usually higher than the disease incidence. In the other words, the plant of corn could be healthy even though infected by maize head smut germ.