Zambia Agribusiness Society

Weeds have serious impacts on agricultural production. It is estimated that in general weeds cause 5% loss in agricultural production in most of the developed countries, 10% loss in less developed countries and 25% loss in least developed countries. In Zambia, yield losses due to weeds are more than those from pests and diseases. Yield losses due to weeds vary with the crops. Every crop is exposed to severe competition from weeds. Most of these weeds are self-sown and they provide competition caused by their faster rate of growth in the initial stages of crop growth. In some crops, the yields are reduced by more than 50% due to weed infestation. 1. Reduced Yield: Weeds compete with crop plants for nutrients, soil moisture, space and sunlight. 2. Poor Crop Quality: Weed seeds contaminate crop yield resulting in poor quality and rejection in the market. 3. Weeds Harbour Pests and Diseases: Weeds harbour organisms, and some are food sources for pests resulting in their increased popula

There are over 250, 000 plant species in the world. About 30, 000 of them occur as weeds in various agro-ecosystems and about 18, 000 of these cause serious damage to crops throughout the world. Weeds today are considered to be the most important pest group which interferes with utilization of land and water resources. The losses caused by them to horticulture are greater than any other pest category. Definition Some of the several definitions given to the term “weed” are listed below. A weed is a plant: 1.     Growing where it is not desired; 2.     Out of place; 3.     Growing where something else should grow or nothing should grow; 4.     Whose potential for harm is greater than for good; 5.     Extremely noxious, useless or poisonous; 6.     Whose economic value has not been discovered. Careful examination and analysis of these definitions indicate that the term “weed” is very much relative to a situation, time, and to an individual concerned. In general, du