Corn bacterial streak disease
Symptoms: Brown to dark brown streaks or leaf spots appear on corn leaves and leaf sheaths. In severe cases, the lesions merge together. Some of the lesions develop into long strips, leading to dark brown, dry leaves. When humidity is high, the infected areas exude a large amount of bacterial ooze. After drying, this oozing turns into a brown, leathery residue that easily falls off after being washed by rain.
Pathogen: The causal agent is *Pseudomonas andropogonis* (E.F. Smith) Stapp., also known as *Pseudomonas striata* or *Woodsii*. It is a rod-shaped bacterium, measuring 1–20.5 × 0.7 μm. It has a single sheathed flagellum, occasionally two unipolar flagella. It does not produce fluorescent pigments, is Gram-negative, and does not form acid. On agar culture media, colonies are round, smooth, white, and shiny, slightly raised, with a slow and sticky growth pattern. The optimal growth temperature ranges from 22–30°C, with a maximum of 37–38°C and a minimum of 5–6°C. It is lethal at 48°C after 10 minutes of exposure.
Host Range: In addition to infecting corn, the pathogen also affects sorghum, legumes, and coffee.
Transmission and Disease Conditions: The bacteria overwinter in infected plant tissues. They spread through wind, rain, insects, or water flow. The pathogen enters through wounds, stomata, or lenticels and then invades internal tissues, causing disease. High temperatures combined with rainy seasons, low-lying fields, compacted soil, and numerous wounds increase the risk of infection. Excessive use of nitrogen fertilizer can also worsen the disease.
Prevention Methods: (1) Encourage the use of compost made from fermented bacteria and apply river mud to fully decompose organic fertilizers. (2) Improve field management by draining water immediately after rainfall in low-lying, wet areas. Regular monitoring and early intervention can help reduce the spread of the disease. Crop rotation and resistant varieties should also be considered as long-term strategies for sustainable control.
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