Northern Corn Leaf Blight (NCLB), caused by the fungus Exserohilum turcicum (previously classified as Helminthosporium turcicum), is becoming an increasingly important foliar disease of corn in the Philippines, particularly in areas with high humidity (due to heavy dew or frequent rain showers) and moderate temperatures (20-28 degrees Celsius).

By Cherry Relevante-Belagantol

The disease affects corn plants at any growth stage, depending on the prevailing weather conditions. Yield reduction can reach 30% if the infection occurs early, i.e. before or during the tasseling stage. NCLB is characterized by long (1-7 inches), narrow, and elliptical grayish-green to tan lesions, which later on produce dark gray or black fungal spores when humidity is high, giving the lesions a dark or “dirty” appearance.

Numerous lesions may form on a leaf, and these lesions can coalesce to form irregular areas of dead tissue when the infection is severe. The spores are produced in as little as one week and these spread to the leaves of new corn plants through rain splashes and air currents. The fungus survives on infected corn debris at the soil surface and builds up over time with a continuous corn cropping system.

Currently, preventive management strategies have been effective in reducing economic losses from NCLB, especially in areas where weather conditions are favorable for disease development. For NCLB-prone areas, the following strategies are recommended:

• Use resistant or moderately resistant corn varieties, if available.

• Practice one-year crop rotation followed by tillage; this will help reduce the inoculum’s density in the soil.

• Apply fungicides (a.i. propiconazole, azoxystrobin, propiconazole + azoxystrobin) at the tasseling to early silking stages to protect the plant and/or minimize infection.

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Reprinted from Usapang Gulayan, an East-West Seed Philippines newsletter.

This appeared in Agriculture Monthly’s May 2015 issue.