Stewart's Bacterial Wilt and Blight
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Symptoms
Early Season Systemic Wilt
- Occur soon after plant emergence
- Yellowed or bleached leaf streaks (photo above)
- Internal vascular discoloration, crown decay, rot (photo below)
- This phase of disease may result in plant death
Later Season Foliar Blight (photos below)
- After tasseling
- Fully developed typical elongated lesions
- Lesions are long, narrow and have a wavy margin
- Yellowish border may be present
- Note blackish appearance of lesions (saprophytic fungal spore production)
- This disease phase rarely results in plant death, but may predispose for stalk rots
Disease Development
Disease is Vectored by Corn Flea Beetles:
- Bacteria overwinter in insect gut
- Beetles feed on plants in spring
- Insect "etches" leaves (whitish areas in photo below)
Two Phases of Disease:
- Early season systemic wilt
- Later season foliar blight
Disease Cycle
Impact on Crop
Yield loss from this disease may occur for a number of reasons:
- Early season systemic wilt reduces stands and weakens plants
- Foliar symptoms reduce functional leaf area, reducing photosynthesis and sugar production
- Stalk rot potential is increased
- When demand for sugars to fill the ear exceeds supply from damaged leaves, the plant takes available sugars from stalks instead, increasing stalk rot potential
Management
Plant Resistant Hybrids
- Pioneer rates its hybrids for resistance
- Contact your local Pioneer sales professional
Control Flea Beetles
- Systemic insecticide seed treatments help to reduce flea beetle populations
- Foliar insecticides may be needed in some cases
- Scout for flea beetles and apply insecticides if insect populations exceed thresholds established by your state
- Predict flea beetle / Stewart's wilt occurrence
- Sum the mean temperature for the months of December, January and February
- Risk increases with the sum of mean temperature - See extension materials from your state
