The symptoms appear as small, oval, water-soaked spots on the lower leaves first. As the disease progresses, they start to appear on the upper part of the plant. Older spots slowly grow into tan, long cigar-shaped necrotic lesions with distinct dark specks and pale green, water-soaked borders. These lesions later coalesce and engulf a large part of the leaf blade and stalk, sometimes leading to death and lodging. If the infection spreads to the upper parts of the plant during the development of the cob. Severe yield losses can occur (up to 70%).
Causes
The fungus overwinters in the soil or on plant debris. Rainfall, night dew, high humidity and moderate temperatures favor the dispersion of the fungus. Carried by wind or rain splashes it first spreads from the soil onto the lower leaves of young maize plants. Rainy conditions and poor field practices favor its spread to other plants and within fields. Optimal temperatures for infection are in the range of 18 to 27°C during the growing season. A prolonged period of 6 to 18 hours of leaf wetness are also necessary. Sorghum is another favorite host of the fungus.
Hosts
Preventive Measure
- Grow resistant or tolerant varieties.
- Ensure balanced nutrient supply and avoid excessive nitrogen fertilization.
- Weed regularly in and around the field.
- Rotate with soybeans, beans, or sunflower to avoid extensive spreading.
- Plow deep to bury plant debris and reduce the amount inoculum in the soil.
Treatment
| Control Dose/Litre | Trade Names |
| 1-2 ml | Tilt, Ridomil MZ, Kavach |