USE OF INSECTICIDES, ATTRACTANTS, AND REPELLENTS 
E. F. Knipling’* 
Man’s chief competitors for food are the insects. Insects and their close relatives 
are vectors of some of the most important diseases of man, animals, and plants. The 
soil harbors hundreds of insect species that feed on planted seeds or the roots of crops. 
Hundreds of other kinds suck the sap of plants, consume foliage, bore into the stems or 
damage the fruit. Still other insect pests attack food or fiber in storage. Every warm- 
blooded animal, including man, is subject to attack by one or more kinds of insects 
that are specific to the host while numerous others attack a wide range of animal hosts. 
Some insects live in water, others are adapted to live only in homes or other structures. 
Thus, among the 10,000 kinds of insects of economic importance in this country, we have 
control problems involving water, soil, cultivated crops, forests, rangelands, stored 
products, livestock, pets, homes, industrial establishments, and man himself. Everyone 
of the 175 million people of this Nation is faced with some insect problems and is, there- 
fore, interested in methods of insect control. 
Progress during the past two decades in dealing with insect pests of agricultural 
crops, livestock, and man, as well as vectors of human diseases, has been outstanding. 
The advances made are due to the close cooperation and combined efforts of scientists 
in various disciplines with Federal and State agencies and private industry. I know of no 
field of the biological sciences in which there has been closer cooperation between in- 
dustry and public-supported research institutions. 
Soil insecticides have come into use that control grubs, wireworms, termites, and 
other soil pests for periods up to 10 years or longer. Many materials are available for 
direct application to plants for the control of pests of fruits, vegetables, forage, grains, 
cotton, and other plants. Long-lasting residual insecticides and aerosols have been de- 
veloped for use in homes to control many household pests and to prevent transmission 
of malaria and other diseases. A number of insecticides and repellents have beende- 
veloped to protect livestock from insect attack. We have insecticides or insect repel- 
lents for direct application to the skin or clothing of man to prevent insect attack or the 
spread of dreaded diseases such as typhus and tick and mite fevers. 
When we consider the scope of insect problems and the extensive use of chemicals 
employed for their control in such wide range of environments, it is apparent that 
potential hazards or conflicts of interests are to be expected. However, before com- 
menting further on this major and continuing problem which confronts entomologists, I 
would like to state that the over-all picture of hazard due to insecticides painted in 
popular or even in some scientific publications by some alarmists is more imaginary 
than real. 
Considering the many insect control chemicals involved and their widescale use, I 
regard the record of safety in insecticide use to be outstanding. Insecticides are re- 
sponsible for fewer accidental deaths than are many of the common household chemicals 
or over-the-counter drugs. There is not a single proved instance of chronic poisoning in 
man due to insecticide residues in foods (Hayes (3)). Local adverse effects to fish and 
wildlife may result from the use of insecticides and every effort must be made to avoid 
such losses. But contrary to implications by some writers, I have seen no evidence of a 
significant decline in the Nation’s resources of fish and game that can be attributed to 
insecticides even in agricultural areas where there is extensive use of insecticides. 
Many instances of adverse effects to beneficial insect parasites and predators resulting 
from the use of insecticides have occurred. Fortunately, however,as reported by Lincoln 
(9), this effect appears to be temporary and there is no evidence of a lasting upset in 
balance between beneficial and destructive insects even in cotton fields where insecticide 
usage is most extensive. 
1Director, Entomology Research Division, Agricultural Research Service, U,S.D,A, 
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