Along with the above related fungal sumptoms, bacterial infections often produce watersoaking around the area where the pathogen entered. Later the lower surface of the leaf will take on a dark, greasy appearance. This greasy appearance is most evident in foliar infections, but can sometimes be seen on other plant organs. Though, these are good indications of a bacterial disease, one must again look for signs of the pathogen. Often, bacterial ooze can be seen coming from a lesion, especially in the morning hours.
Some bacterial diseases have distinctive odors.
An easy test to determine if wilt symptoms are caused by bacteria is called a bacterial streaming test. This may be done by cutting the stem horizontally and inserting it into a jar of water. If bacteria are present, they will produce a cloudy stream within a few minutes. This stream is composed of millions of bacteria. In order to get a definitive diagnosis of a virus, samples must be sent to a clinic which has the special equipment necessary to do the proper tests.