weed-control needs of the future and the in- 
tegration of chemical and nonchemical meth- 
ods in crop, range, and forest production and 
the utilization of water resources and non- 
crop land areas. 
Trends since 1944 strongly suggest that the 
use of herbicides will continue to expand at 
an equal or more rapid rate inthe future (4, 5, 
8, 9). All available survey data, as well as the 
requirements for efficient mechanized crop 
production, strongly indicate a continued ex- 
pansion of herbicide usage. 
Because herbicides are used to kill plants 
classified as pests, they are also appropriately 
called pesticides. Herbicides are, however, 
more than pesticides or protectants. They are 
crop-production chemicals, which reduce the 
man-hour, machine-hour, and machine-horse- 
power requirements of crop production, Their 
effects on other crop-production practices are 
also far reaching, 
New chemical methods of weed control will 
affect choice of crop and variety; seedbed 
preparation; method of seeding; seeding rates; 
row spacing; plant spacing in the row; plant 
population; fertilization practices including 
type, time of application, and placement; cul- 
tivation; irrigation practices; harvesting; 
seed-cleaning operations; erosion control; 
fallow practices for weed control; disease- 
and insect-control practices; pasture renova- 
tion; pasture and range management; clearing 
new lands for crops or pasture; forest man- 
agement; utilization of farm water resources 
for irrigation and recreation; and maintenance 
of reservoirs, drainage ditches, ditchbanks; 
irrigation canals, and arm roadsides. 
Increased specificity and selectivity will be 
essential requirements of herbicides in the 
future. Highly specific herbicides will be used 
to control specific weeds in specific crops 
and on noncrop lands utilized for specialized 
purposes. There will also be increasing de- 
mands for broad-spectrum herbicides for the 
control of diverse weed populations but without 
broad-spectrum toxicity to crops and non- 
target organisms in the total environment. 
The fundamental requirements for future 
expanded use of herbicides without harmful 
effects in man's total environment can and 
must be accomplished. 
26 
BASIC RESEARCH IS KEY TO 
FUTURE HERBICIDE 
REQUIREMENTS 
In order to achieve the requirements for 
herbicides in the future, our fundamental 
knowledge of the relation between molecular 
structure and herbicidal activity must be ex- 
panded, A better understanding of the pene- 
tration, absorption, and translocation of her- 
bicides in plants must be developed. The 
mechanisms of phytotoxicity and selective ac- 
tion must be more fully determined. The fate 
of herbicides in plants and soils and our total 
environment must be more fully understood, 
including primary, secondary, and cumulative 
effects on nontarget organisms (2, 6; fig. 2). 
The results of the total weed science re- 
search effort in meeting the present require- 
ments for herbicides provide a basis for 
optimism that the herbicide requirements of 
the future can also be attained (2). A few 
selected examples will illustrate some of the 
principles that will need extension in the 
future. The use of surfactants, cosolvents, 
carriers, and other formulation ingredients, 
based on knowledge of the entrance and move- 
ment of herbicides in plants and their per- 
sistence, will reduce herbicide rates of appli- 
cation, decrease or increase persistence, 
lower the cost of application, and prevent or 
minimize residues in plants and soils. Such 
knowledge also permits use of low or nontoxic 
ingredients to reduce the amounts of higher 
toxicity ingredients in the formulation. The 
development of the 3-(3,4-dichlorophenyl)-1, 
1-dimenthylurea (diuron)-surfactant treat- 
ment, as a directed postemergence applica- 
tion for weed control in cotton, is an excellent 
example of utilizing this principle in develop- 
ing a widely used, safe, and effective practice. 
Research on the mechanisms of action of 
herbicides has revealed that plants differ in 
their capacity to metabolize herbicides and 
that this property is highly specific. The con- 
version of a nonphytotoxic chemical, 4-(2,4- 
dichlorophenoxy) butyric acid (2,4-DB), to the 
highly effective herbicide, 2,4-dichlorophe- 
noxyacetic acid (2,4-D), by some weeds while 
certain crops do not cause this conversion 
provides a highly selective mechanism of 
