COMPARISONS OF THE DISEASE-REDUCING EFFECTS AGAINST RICE BACTERIAL LEAF BLIGHT OF AQUEOUS LEAF EXTRACTS OF Ageratum conyzoides AND Chromolaena odorata

Abstract

Bacterial leaf blight dramatically reduces rice yield and quality, particularly during wet seasons. Disease-reducing effects of the aqueous leaf extracts of Ageratum conyzoides and Chromolaena odorata were observed under net house conditions. This study aimed at comparing the effects of these extracts using two application methods, i.e., seed soaking 24 hrs before sowing and combinations of seed soaking and foliar spraying either 7 or 14 days before pathogen inoculation (DBI). Using seed soaking, the 3%, 4% and 5% (w/v) extracts of A. conyzoides and 4% and 5% C. odorata showed similar effects as that of the chemical control (Starner 20 WP) where the effects of A. conyzoides were lower compared to those of C. odorata. Seed soaking combined with foliar spraying exhibited higher effects than seed soaking did. For A. conyzoides extracts, combinations of seed soaking and foliar spraying 7 DBI provided higher effects than combinations of seed soaking and foliar spraying 14 DBI did, where the highest effects were obtained using 3% for seed soaking and 4% for foliar spraying 7 DBI (56.3%). In contrast, combinations of seed soaking and foliar spraying 14 DBI using C. odorata extracts provided higher effects than combinations of seed soaking and foliar spraying 7 DBI did, where the highest effects were obtained using 4% for seed soaking and 5% for foliar spraying 14 DBI (56.1%).