Biological control of weeds and plant pathogens in paddy rice by exploiting plant allelopathy: an overview

The allelopathic properties of plants can be exploited successfully as a tool for pathogen and weed reduction. Over a decade, preliminary surveys of some hundred allelopathic plants in the Southeast Asia and Japan ecosystems were made, and more than 30 species including crops which exhibited the greatest allelopathic potential were selected and examined for their impacts on emergence of pathogens and weeds. Observations showed that application of these plant materials at 1-2 tonne ha(-1) can reduce weed biomass by about 70%, and increase rice yield by about 20%. Some species showed strong inhibition on major plant pathogens and they might become effective tools in reducing plant pathogens and weeds. However, application of 1-2 tonne ha(-1) of plant material to the field makes heavy fieldwork. Numerous growth inhibitors identified from these allelopathic plants are responsible for their allelopathic properties and may be a useful source for the future development of bio-herbicides and pesticides. (C) 2004 Elsevier Ltd. All rights reserved.