(1) Losses that are unpreventable with present technological 
knowledge. There may not be any known way of completely 
preventing reductions in crop yields caused by certain 
diseases and insects. Similarly, there may be no known 
use for certain byproducts or materials, 
(2) Losses that are presumably preventable, but only through the 
use of control measures that are not economically feasible 
with present technical knowledge and under current economic 
conditions, It may be possible to prevent the reduction in 
certain crop yields due to some insects or diseases by apply- 
ing sufficient pesticides at the required times, but it may 
not pay the farmer to do so because the cost would exceed the 
additional value of the product, 
(3) Losses that are preventable with present technical knowledge 
and under current economic conditions. It is possible to 
minimize or prevent some reductions in crop yields caused by 
insects and diseases by proper control measures, and it also 
is profitable for farmers to use such measures, But frequently 
they may not do so because they lack knowledge of recommendations 
or have no funds to pay the additional operating costs or to 
make the necessary capital investments. 
With the accumulation of new technical knowledge resulting from research, 
losses that formerly were not physically preventable may become so. They 
also may become economically preventable, 
Changes in économic conditions may make it economically feasible to pre~ 
vent losses from certain causes. For example, expansion in market demand 
and higher prices for farm products would make it profitable for farmers 
to put into effect certain control measures which previously were not 
profitable, Similarly, reduction in prices paid by farmers for materials 
required for preventing losses would make additional control measures 
profitable. The costs of fertilizers and lime are directly related to 
problems of soil conservation. 
It is recognized that only part of the causes of loss could be prevented 
even if present technological knowlege could be fully put into effect. 
Some of the factors preventing full utilization of the most advanced 
agricultural techniques are - (1) adverse weather, preventing spraying 
and similar contre] operations at the proper times (2) natural inertia of 
some producers and handlers to adopt the most effective protective measures; 
(3) nonavailability of pesticides, proper equipment, or seed of resistant 
varieties; (lh) competition with other farm operations, which often delays 
the use of contre] measures until after the most effective time; (5) some 
control measures involve too mich equininent, labor, or expense to be 
profitable under present economic conditions; and (6) lack of knowledge 
of the most effective protective measures, a difficulty that can be over- 
_come only through an increased educational program. 
aoe 
