Arkansas Rice: Leaf Blast Makes An Early Showing

In 2018, initial symptoms of leaf blast on the rice cultivar Titan were reported from Lonoke County on June 6 in rice that was at early tillering.

The field is surrounded by trees and has a history of blast. Titan is a medium-grain rice and was rated moderately susceptible to blast since its release. It has been less susceptible than Jupiter to blast in our greenhouse tests and under field conditions.

Initial symptoms of blast may not be clear and can be confused with herbicide damage or brown spot. To confirm symptoms, leaves with lesions should be incubated in moist chamber to encourage sporulation. Spores can be clearly viewed under a compound microscope at 100X magnification.

Spores are typically pear-shaped with 2 septa.

Fungicide application may not be needed unless blast is burning down the leaves. Leaf blast is often suppressed by increasing flood and maintaining a depth to at least 4 inches.

Blast fungus spores under magnification.

The spores of the fungus are lightweight and can be carried by wind for several miles. In fields with a history of blast and planted with susceptible varieties, the recommendation is for two timely protective fungicide applications for late-season neck and panicle blast. Those are the most devastating forms, causing potentially near 100% grain yield loss. Distinctive lesions from leaf blast are diamond-shaped with ashy centers .

Often, the first blast report on rice in Arkansas comes in the second to third week of June, so it seems unusual to see blast this early. However, the hot conditions have made flood depth management difficult and, combined with heavy morning dews, could contribute to increased blast infection.


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