action on specific pests, as well as improve- 
ments in ways to apply pesticides, would be 
important in the use of such measures, 
Although nonchemical methods for pest con- 
trol are intriguing, they also have weaknesses, 
Entomologists have shown that parasites and 
predators have adjusted over the years to a 
balance with their hosts such that they kill 
some but not all of them, Complete host de- 
struction would eliminate the parasite or 
predator by destroying its food supply, Thus, 
control of the pest is seldom complete enough 
to prevent economic damage, Furthermore, 
reduction of the pest population is rarely 
sufficient to prevent its becoming dense again, 
An insect host may become resistant to a natu- 
ral enemy just as it may develop resistance to 
chemical controls (29), Therefore, we will 
expect to rely generally on supplemental 
chemical treatment of the infected plant or 
animal for many years to come (5), 
Individuals in industry have long been aware 
of need for "ideal'' application of pesticides, 
but they still admit to having only a broad 
concept of the job their application equipment 
is supposed to do (10), We in the research 
field have not yettoldthem the optimum deposit 
pattern for control of specific pests with 
particular chemicals, The development of 
pesticide application techniques and equipment 
should parallel the work on chemical develop- 
ment (17), Ideally, the pesticide, its applica- 
tion techniques, and, if needed, special applica- 
tion equipment should become available to the 
user Simultaneously, Unfortunately pesticides 
are developed, recommended, and sold without 
adequate research on application equipment or 
techniques, 
Certain assumptions may be made with re- 
spect to reduction of the residues from chemical 
application (18), Of course, the ideal solution 
to reduce residues is elimination of the need 
for chemicals (14), But if chemicals are to be 
used, only the minimum amount for optimum 
control should be used (23), with application 
of the right kind of chemical inthe right place, 
at the right time, in the correct amount, and 
properly distributed for the needs (9), 
Improved equipment to deposit chemicals in 
predetermined locations not only would in- 
crease the effectiveness of pesticides but also 
would reduce substantially the amount needed 
for optimum control, This, in turn, would 
203 
reduce the cost to farmers and reduce drift 
and residue hazard to man, animals, beneficial 
insects, and crops, Although present equip- 
ment and techniques of applications have re- 
sulted in substantial gains to agriculture, 
methods are still relatively crude and ap- 
plication efficiency is low, 
Development and design engineers are 
hampered in creating and producing more ef- 
ficient equipment for applying chemicals by 
the lack of basic knowledge about the behavior 
of materials during and after application (1). 
Increased basic research is needed to deter- 
mine the complex effects of physical factors 
on the movement of chemical particles from 
the time they leave the applicator untilthey are 
deposited, In addition to the size of particles 
and droplets, these factors include aero- 
dynamic and inertial effects, gravitational and 
electrical forces, and temperature gradient 
effects, 
Despite out acknowledgement that several 
disciplines should be concerned with pesticide 
application, we believe that many of the phys- 
ical and engineering aspects can be considered 
in isolation from entomological, pathological, 
and crop-production problems, provided these 
aspects are treated in general terms, Wewill, 
therefore, limit our discussion to considera- 
tion of these aspects, 
PUBLIC SERVICE RESEARCH 
Research for the determination of basic 
equipment requirements for given sets of con- 
ditions can frequently be conducted more ef- 
fectively and at lower cost by the public 
research agencies because of facilities already 
available for other fields of research, In many 
cases, private or cooperative interests may 
not be justified in undertaking research where 
the costs may be more than the pioneering 
company can recover, There is also the pos- 
sibility that the net return fromthe sale of new 
or improved equipment may be no more or 
even less than that of the machines replaced 
(20), Industry, particularly the smaller manu- 
facturers, must invest its limited research and 
development money in projects that will bring 
relatively short-range monetary return. Since 
public service agencies can justify projects 
on the basis of potential improvement in the 
