Most plant diseases – around 85 percent – are caused by fungal or fungal-like organisms
There are approximately 200 types of bacteria that cause diseases in plants. They are most active in warm and humid environments.
There are two ways for us to determine what kind of plant pathogen (fungi or bacteria) we’re dealing with: looking at the disease symptoms displayed by the plant and using the microscope to check for fungal spores or bacterial oozing. When we look at the plant’s symptoms, there are a few that tend to indicate a bacterial infection. Yellow haloing around lesions on leaves is one sign of bacterial disease (though there are several fungi that can cause similar symptoms). Bacterial lesions tend to be limited by veins in the leaves. We also suspect bacteria when we find sticky exudate or stringy ooze in diseased tissue.