14 



MISCELLANEOUS PUBLICATION NO. 1065, U.S. DEPARTMENT OF AGRICULTURE 



farmhouse, in a rural community, or on a forest 

 recreation area depends on reasonably good hy- 

 draulic conductivity of the soil around the dis- 

 tributing tiles. Reports of malfunctioning septic 

 systems are common. Design of septic systems 

 could be improved; they could be better adjusted 

 to soil characteristics and to degree and nature of 

 probable detergent load. 



No hazard to humans or animals is apparent 

 from the presence of detergents in surface waters. 



Detergents carry phosphate as an active com- 

 ponent. When sewage effluents enter rivers, lakes, 

 and estuaries, this phosphate becomes a key plant 

 nutrient promoting the development of obnoxious 

 algal blooms. This role of phosphate is discussed in 

 the section on plant nutrients. Much more factual 

 information is needed on the respective contribu- 

 tions of phosphate from detergents and sewage in 

 general compared to that from land runoff. 



Insecticides 



The potential contamination of the environment 

 by pesticides, particularly the chlorinated hydro- 

 carbons, has been a matter of public and private 

 discussions. Within a few years after DDT began 

 to be used extensively as a field and forest insecti- 

 cide, DDT and its metabolites were found in the 

 fatty tissues of fish and wildlife, both living and 

 dead. Newspapers carried features on fish and 

 wildlife losses with an implicit indictment of agri- 

 culture and forestry for having used insecticides. 



The use of these chemical tools has made a tre- 

 mendous contribution to man's health and welfare 

 over the past 25 years. Unfortunately, in some in- 

 stances, they have also been abused and misused 

 without due consideration to their impact on the 

 nontarget organisms. 



In 1964. 4-70 million pounds of insecticides were 

 used on 83 million acres of land. In a few instances, 

 adverse effects have occurred in agriculture and 

 forestry. Insecticides that have broad spectrum ac- 

 tivity are just as effective on many nontarget in- 

 sects as on the target ones. For example, use of cer- 

 tain insecticides has resulted in losses of honeybees 

 and other beneficial insects. 



The application of certain insecticides to cotton, 

 corn, or other crops may lead to insecticide residues 

 in soybeans or peanuts grown in the soil a year or 

 more later. Certain chlorinated hydrocarbons can 

 persist in soil for many years. In one experimental 

 study 50 percent of the original high-level applica- 



tion of DDT was found in the soil 8 years after the 

 material had been applied. 



The pesticide monitoring program maintained 

 by the U.S. Department of Agriculture on wide- 

 spread soils and waters is, therefore, exceedingly 

 important. Evidence revealed from these monitor- 

 ing activities does not show cause for concern on 

 pesticide buildup. But this does not warrant com- 

 placency over the diverse problems stemming from 

 insecticide use. 



Over the long pull, research efforts towards 

 avoiding the adverse effects of insecticide residues 

 in the environment must continue to receive major 

 attention. 



Far better information is needed on insect 

 population trends with the objective that emer- 

 gency use of chemicals may be avoided. 



Research on developing insecticides with higher 

 biodegradability and lower persistence in the en- 

 vironment must move forward apace. 



There needs to be far better information on 

 the chemical behavior of insecticides in soils vary- 

 ing widely in physico-chemical attributes. The 

 extent and level of pesticides in waters and in 

 soil- water systems must be better evaluated and 

 the significance of the findings better understood. 



Certain residue problems arise as a result of 

 spray or dust drift beyond the target area. There 

 are good possibilities of developing better methods 

 of application or lower application rates. These 

 must be pursued. 



The use of physical attractants to aid in non- 

 chemical control of economic insects needs to be 

 more fully explored. 



All possible support should be allocated to re- 

 search for completely selective methods of con- 

 trolling major insect pests. These techniques in- 

 clude the use of predators and dissemination of 

 specific insect diseases; development of specific 

 insect attractants; breeding and selection of insect 

 diseases: breeding and selection of insect-resist- 

 ant crop varieties; the use of self-destruction 

 mechanisms such as release of sterile males; and 

 the development of chemical insecticides that act 

 on selective physiological systems peculiar to the 

 target insect. 



Herbicides 



Weed control by use of selective herbicides has 

 increased substantially during the past 20 years. 

 In 1964, 1S4 million pounds of herbicides were 



