1) The drop of foliage from plants caused by herbicides such as Agent Orange, diuron, triazines, all of which interfere with photosynthesis. The use of defoliants, as in Vietnam or in jungle clearance for agriculture, can permanently destroy tropical forests. Once the tree cover is removed, the soil is subjected to erosion and precious nutrients are rapidly leached away. 2) Destroying (an area of jungle, forest, etc.) as by chemical sprays or incendiary bombs, in order to give enemy troops or guerilla forces no place of concealment.