Bacterial stalk rot of corn

The causative agent of this disease is the bacterium Erwinia carotovora (often classified as Pectobacterium carotovorum), a gram-negative rod-shaped bacterium. It causes wet rot by producing enzymes that degrade the cell walls of the host plant, leading to the collapse of internal tissues.

The disease primarily affects corn (maize), particularly when plants are in a succulent growth stage. However, it is an opportunistic pathogen that can also attack a wide variety of vegetable crops, including potato tubers, onions, and various leafy greens, creating significant challenges for crop rotation management.

Symptoms typically begin with water-soaked lesions on the lower internodes of the stalk. As the bacteria multiply and secrete macerating enzymes, the inner pith tissue turns into a mushy, foul-smelling mass. The leaves may wilt rapidly, and the weakened stalks often collapse during windy conditions, leading to significant yield losses.

Development is highly dependent on environmental conditions, specifically high temperatures (above 25°C) and excessive moisture. The bacteria thrive in water films, spreading through irrigation water, rainfall splashing, or contaminated agricultural equipment. Insects feeding on the stalks often serve as primary vectors for the pathogen.

Management strategies focus on prevention, as there is no effective chemical cure for established bacterial infections. Key practices include improving field drainage, choosing resistant hybrid varieties, and strictly controlling insect pests that create entry wounds for the bacteria. Sanitation of tools and field equipment is also essential to prevent the spread of the pathogen.