Disease-reducing effects of aqueous plant extracts against rice bacterial leaf blight (Xanthomonas oryzae pv. oryzae) under greenhouse conditions

Bacterial leaf blight (Xanthomonas oryzae pv. oryzae) is one of the most serious diseases of rice. Alternative strategies have been developed to control the disease where the use of plant extracts has increasingly been focused. Aqueous extracts of the ten commonly found plants in the Mekong Delta of Vietnam were selected to screen for those having disease-reducing effects under greenhouse conditions. The effects were observed when rice seeds were treated with the nine extracts including Chromolaena odorata (cỏ hôi), Lantaca camara (trâm ổi), Kalanchoe pinnata (sống đời), Ageratum conyzoides (cỏ cứt heo), Ocimum sanctum (húng quế), Eclipta prostrate (cỏ mực), Allium sativum (tỏi), Azadirachta indica (neem) and Datura metel (cà độc dược). These extracts did not show any adverse effects on the germination and development of rice seeds. Similar effects compared to that of the chemical control were recorded from the treatments using 1% and 2% (w/v) extracts of Ageratum conyzoides and Kalanchoe pinnata. The effects were maintained until 21 days after pathogen inoculation.