Herbicide use history and weed management in Southeast Asia

Southeast Asia's rich natural resources and favorable climatic conditions make it conducive for intensive rice-based, corn-based and perennial crops-based cropping systems. Regardless of the cropping system, weeds remain to be among the major factors that limit yields. The use of herbicides to manage weeds in these systems has been increasing through the years. The use of 2,4-D started in the late 1940s and remains as a major herbicide to control rice weeds. The 1980s saw the introduction of multiple active ingredients of herbicides for rice, corn and perennial crops, mostly selective herbicides with highly specific target sites and MOA. Glyphosate, commonly used in perennial crop-based systems, is now used at pre-planting in rice and corn and post-emergence in genetically modified corn. The intensive and continuous use of herbicides resulted in resistance development in weeds. To date, 37 unique cases of herbicide resistance are reported involving 17 weed species and 30 active ingredients. The rise in herbicide resistance and environmental pollution is largely due to insufficient farmer education on proper use of herbicides and integrated weed management, poor product stewardship, and lax implementation of pesticide policies and regulations. A sustainable weed management approach that embraces integrated and precise weed management is needed. We propose a sustainable weed management framework involving the various stakeholders to strengthen partnership, improve implementation and formulation of fair policies and regulations for the industry, increase investment in research and development of appropriate weed control technologies, and educate farmers, industry players and the general public.