Common bacterial diseases that affect plants include fire blight, bacterial leaf spot, bacterial wilt, crown gall, and soft rot.

Fire Blight
Fire blight is a bacterial disease that primarily impacts certain species of fruit trees and ornamental shrubs. It is caused by the bacterium $Erwinia\ amylovora$ and is characterized by a scorched appearance of the affected branches. The disease can spread rapidly under favorable conditions, leading to significant crop losses.

Bacterial Leaf Spot
Bacterial leaf spot is caused by various species from the genera $Xanthomonas$ and $Pseudomonas$. This disease affects a wide range of plants, resulting in water-soaked spots on the leaves that eventually turn brown or black. In severe cases, bacterial leaf spot can lead to defoliation and a reduction in yield.

Bacterial Wilt
Bacterial wilt is a serious disease that affects crops such as tomatoes, potatoes, and bananas. It is caused by the bacterium $Ralstonia\ solanacearum$. This bacterium invades the plant’s vascular system, obstructing water transport and ultimately causing the plant to wilt and die.

Crown Gall
Crown gall is a disease induced by the bacterium $Agrobacterium\ tumefaciens$. It affects a wide array of plants, leading to the formation of large, tumor-like growths at the base of the stem or on the roots. These galls can disrupt the flow of nutrients and water, weakening the plant and diminishing its yield.

Soft Rot
Soft rot is a prevalent disease in many vegetable crops, caused by various species within the genera $Pectobacterium$ and $Dickeya$. This disease leads to the decay of plant tissues, often culminating in the complete collapse of the plant. The bacteria responsible for soft rot are commonly found in the soil and can survive for extended periods in plant debris.

These bacterial diseases can result in significant economic losses in both agriculture and horticulture. Management strategies typically involve a combination of cultural practices, such as crop rotation and sanitation, along with the use of resistant plant varieties. In certain situations, chemical control measures may also be employed.