Northen leaf blight of maize

C/O: Setosphaeria turcica (anamorph: Exserohilum turcicum)

Symptoms:

• Early symptoms appear as long, narrow, tan lesions that form parallel to leaf margins (Fig1).
• As these lesions develop, the classic symptoms of NCLB will be observed: long, oblong, or “cigarshaped” tan or grayish lesions (Fig2).
• The lesions produce olive-green or black fungal spores when humidity is high, which can give the lesions a dark or dirty appearance.
• Generally, disease is more severe after tasseling due to the nutritional variation in crop stages.

Etiology:

• Facultative saprophyte
• Conidiophores: 2-6 in number, emerge from stomata, brown in color, 2-4 septa
• Conidia: 3-8 septa (may be true or pseudo), Straight or slightly curved, widest at the center, presence of hilum.

Favorable condition:

• Relatively cool, wet seasons, 6 hours of leaf wetness, temperature 18 and 27 °C
• Sporulation requires a 14-hour dew period between 20 and 25 °C.
• Sporulation often occurs during nighttime and is halted when humidity falls during the day.
• Infection is inhibited by high light intensity and warm temperatures.

Survive and spread:

• Survive: Perithecium containing asci with ascospores and conidiophore as resting stage which present on soil, crop debris etc.
• Spread: wind borne conidia.

Disease cycle:

• Polycyclic disease

Management:

• Use disease free
• Rotation with non-susceptible crops
• Collect and destroy infected plant debris
• Treat the seeds with Captan or Thiram at 4 g/kg.
• Spray the crop with Mancozeb@0.25% at the age of 40 days and the spraying have to be repeated twice at 15 days