FOOD PRODUCTIVITY POTENTIAL 
PERENNIAL 
GRASSES AND 
WEEOS 
CLIMAX 
VEGETATION 
woody 
SHRUBS 
ANNUAL 
WEEOS 

LOW=VALUE HIGH=VALUE 
GROPS CROPS 
VEGETATIVE COMPOSITION 
SCIENTIFIC TECHNOLOGY ————» 
<> NATURAL SUCCESSION 
Figure 1,--(From Shaw et al, (6),) 
These are the active ingredients of man's 
existence and survival. Weeds damage the 
total economy. 
The annual losses due to weeds are about 
$2-1/2 billion. In addition, farmers spend 
about $2-1/2 billion each year to control weeds, 
Thus, the losses due to weeds and the cost of 
their control in the United States are esti- 
mated to exceed $5 billion each year (7). 
Scientists have accepted the weed challenge, 
and they have turned weed science into a 
revolution, which has advanced through a 
succession of control techniques and methods 
that involve the use of energy of man and 
livestock, as well as mechanical devices 
ranging from the sickle to the diesel tractor, 
But laborious methods of hand weed control, 
such as the hoe and machete, have remained 
with us in many parts of the world as obstacles 
to the efficient mechanization of crop pro- 
duction. 
One of the most important objectives of 
research and of regulatory and educational 
programs is the reduction of weed losses and 
the cost of their control by effective methods 
24 
that do not injure man, animals, plants, soil, 
forests, fish, or wildlife. Through science and 
technology, chemicals have been developed to 
replace physical energy for weed control. 
This development has opened new horizons 
for increasing the efficiency of American 
agriculture. This significant advance has also 
created some problems that will require a 
constant review of research and educational 
programs (1). 
The purpose of this paper is to review some 
of the requirements of chemical weed control 
of the future as a primary method and in 
combination with ecological, cultural, mechan- 
ical, biological, and other methods. 
SCOPE AND USE OF CHEMICAL- 
CULTURAL WEED-CONTROL 
METHODS 
The weed-control operations in the United 
States almost defy imagination. Cultural, me- 
chanical, ecological, and other biological 
methods of weed control are used on 365 
