AGE-MEDIATED RESISTANCE AND FUNGICIDE APPLICATION FOR LEAF BLAST CONTROL IN UPLAND RICE

The effect of age-mediated resistance and a single foliar fungicide ap plication of tricyclazole (0 . 262 kg a.i./ha) on leaf blast control i n upland rice was studied in two field experiments during 1984-86. Lea f blast in the upper two leaves was significantly reduced with an incr ease in plant age. he relationship between the leaf blast and plant ag e was exponential. A similar pattern was obtained for the individual t op three leaves. The estimated leaf blast severity levels of partially -emerged leaves at the time of fungicide application, top fully-emerge d leaves and penultimate leaves in the 52-day-old plants were reduced to 60%, 37% and 33%, respectively, in the 60-day-old plants. In genera l, fungicide spray reduced the number of expanded sporulating lesions in the top fully-emerged and penultimate leaves. Despite reduction in leaf blast severities the lack of significant yield response to a sing le fungicide spray does not warrant control at the vegetative phase of crop growth.