Integrated Weed Management

Integrated Weed Management (IWM)


Weeds are important biotic constraint to food production. Weeds compete with crops for the same resources, basically water, nutrients, light and carbon dioxide. Furthermore, they are alternate hosts for crop pests and pathogens. Moreover, some of them lack autotrophy and fully develop only by parasitizing crops or wild hosts. Globalization of trade and weak legislations on weed control in most of the developing countries has favored spread of Invasive Alien Plants (IAP).

A farmer learning to use a rotating hoe for weed control in a Farmer Field School rice paddy in Senegal. ©FAO/Olivier Asselin

Weeds, in general, precede crops on farming lands and are major yield reducing factors. In ecological terms, most annual weeds are r-strategists, establishing populations with high relative growth rate (r). Thus, they produce numerous viable seeds and their populations quickly build up, in an exponential pattern. Weed competition with crops reduces agricultural output (quantity and quality), and increases external costs by spreading them across farm boundaries. It is also a major constraint to increased farmers’ productivity, particularly in developing countries where weed control claims 20 to 50 % of farmers’ time and keep smallholders in a vicious circle of poverty.

Taking into consideration the importance of weeds, FAO assists member countries to strengthen national and regional capabilities of the developing world in the implementation of programmes and/or activities on Integrated Weed Management. Capitalizing on existing knowledge and FAO’s experience, the strategy for promoting integrated weed management is based on three pillars:

1.       Community level with practical integrated weed management options and capacity building

2.       National level with institutional, regulatory and legislative policy guidance and capacity building

3.       Regional level for concerted policy measures and capacity building on specific weed management issues.

©FAO/Jon Spaull