Northern Corn Leaf Blight
Beginner
Scientific Name
Exserohilum turcicum
Identification
- Causes long, elliptical (2- 15 cm, 1- 6 in.) greyish-green or tan streaks
- Lesions most often begin on the lower leaves
- As the disease develops, lesions may join, forming large blighted areas
- Entire leaves may become blighted or “burned”
Often Confused With
Stewart’s wilt
Period of Activity
Northern corn leaf blight is found during warm, wet growing conditions. It often first appears at the time of silking or later.
Scouting Notes
Examine 10 or more plants at 10 locations throughout a field looking for symptoms of northern corn leaf blight.
Thresholds
None established. Fungicides are most effective when applied at the early onset of the disease.
Advanced
Scientific Name
Exserohilum turcicum
Identification
The disease appears as long, elliptical (2- 15 cm (1- 6 in.)), greyish-green or tan streaks. Lesions most often begin on the lower leaves. As the disease develops, individual lesions may join, forming large blighted areas. In some cases the entire leaves may become blighted or "burned". Losses due to northern leaf blight are most severe when the leaves above the ear are infected at, or slightly after pollination.
Northern corn leaf blight is more common on field corn varieties. Due to the shorter growing season, sweet corn fields are less likely to suffer serious losses due to this disease.
Often Confused With
Stewart’s wilt
Biology
The fungus survives in corn residue as either spores or fungal strands (mycelium). The spores of the fungus are spread from the ground residue to the developing corn plant through wind or rain splashing.
Plants that become infected act as a secondary source of infection and may spread to other fields. Disease development is favoured by moderate temperatures (18- 27°C or 64- 81°F) with prolonged periods of humid or rainy weather.
Period of Activity
Northern corn leaf blight is found mostly during warm, wet periods during the growing season, at the time of silking or after.
Scouting Notes
Examine 10 plants at 10 locations throughout a field looking for symptoms of northern corn leaf blight.
Thresholds
None established. Fungicides are most effective when applied at the early onset of the disease.
Management Notes
- Crop rotation and tillage will reduce inoculum levels in surface residues. In reduced tillage systems, rotation and resistance are necessary.
