PART X — ENVIRONMENTAL CONTAMINANTS 



on natural enemies requires repetition 

 of applications. This increases the 

 selection pressure for resistance in 

 some cases and hastens the develop- 

 ment of populations resistant to the 

 chemical. 



Persistence of a pesticide chemical 

 is not in itself an undesirable quality. 

 Normally, we need some level of per- 

 sistence for pest control. This is es- 

 pecially true when the pest popula- 

 tion moves slowly into a susceptible 

 stage of development or out of hiber- 

 nation quarters or other inaccessible 

 or unbeatable habitats into the area 

 of contact with the pesticide. If the 

 movement into the area to be pro- 

 tected extends over an appreciable 

 length of time, the pesticide must 

 persist over this length of time or 

 else repeated treatments with a non- 

 persistent material will be necessary. 

 In general, the latter procedure will 

 be more costly and more hazardous. 

 Persistence is a disadvantage when it 

 is the cause of undesirable residues 

 on the harvested crop or elsewhere 

 in the agro-ecosystem, or when the 

 pesticide is concentrated through food 

 chains to harmful levels in non-target 

 organisms. (See Figure X-14) Again 

 we must strike a balance between 

 costs of alternative procedures and 

 between the benefits and undesirable 

 effects of these procedures. This com- 

 parison should not be made only in 

 narrow economic terms but also with 

 full consideration of the social costs 

 and benefits. 



Guidelines for Good 

 Pest Management 



Today many decisions with respect 

 to pest control are being made in a 

 political context and with little con- 

 sideration of the fundamental tech- 

 nological facts upon which sound 

 pest-control decisions should be 

 based. Each pesticide usage should 

 be judged on the basis of the poten- 



Figure X-14 — CONCENTRATION OF DDT 

 IN A LAKE MICHIGAN FOOD CHAIN 



The table shows why minute quan- 

 tities of DDT in lake water are a 

 serious problem. The rate of ac- 

 cumulation is proportional to the 

 concentration of DDT in the water 

 multiplied by the time of exposure. 

 By the time DDT reaches fish, its 

 level of concentration can cause 

 reproductive failure. These con- 

 centrations in the fish in turn be- 

 come a hazard to the piscivorous 

 birds at the top of the food chain. 

 Retention time for DDT in water 

 averages 30.8 years. No solution 

 to the problem is yet evident. 



tial positive values to be achieved 

 by such usage as weighed against 

 the possible negative values occurring 

 from residues on the harvested crop, 

 occupational hazards to humans, haz- 

 ards to pollinating and other benefi- 

 cial insects, effects on wildlife, the 

 contribution to total environmental 

 pollution, and other direct or subtle 

 effects. Each use of a chemical must 

 be judged independently. Banning 

 all uses of a chemical is unwise unless 

 it is clear that all uses of that chemi- 

 cal are harmful. Likewise, it is ir- 

 responsible to advocate the total 

 replacement of pesticides with so- 

 phisticated but poorly tested alterna- 

 tive pest-control techniques. It is a 

 disservice to society to discard the 

 good crop-protection methodology 



currently available and to adopt in its 

 place a glamorous new but untested 

 methodology. In the future develop- 

 ment of crop protection for a world 

 agriculture, it will be just as impor- 

 tant to apply the methodology of 

 traditional pest-control techniques as 

 it will be to find revolutionary new 

 approaches, some of which may be 

 expected to have little or no practical 

 value. 



Research — In the interest of a bet- 

 ter environment, the integrated con- 

 trol concept must be fostered among 

 pest-control researchers, and research 

 on pest-management systems should 

 expand as rapidly as possible. There 

 is a critical need for information on 

 many aspects of integrated control, 

 including pest economic thresholds, 

 natural control, ecology, phenology, 

 and the nature of agro-ecosystems. 

 Such studies will provide informa- 

 tion permitting better timing and 

 placement of insecticidal treatments 

 and will lead to the development of 

 alternative control measures. Studies 

 of this sort are currently being sup- 

 ported by federal and state agencies 

 and some of the commodity groups, 

 but the need exists for greatly ex- 

 panded support. 



Manpower Training — The more 

 sophisticated controls and integrated 

 control systems will create a demand 

 for more highly qualified people in 

 pest control. Consequently, there is 

 an urgent need to develop, simultane- 

 ously, training programs for ecologi- 

 cally oriented pest-control advisers. 

 Practicing economic entomologists 

 versed in the principles of integrated 

 control are extremely rare today and 

 badly needed for an ecological ap- 

 proach to pest control. The training 

 of a new corps of researchers and 

 advisers well versed in integrated 

 control will entail careful planning 

 and the development of a new type 

 of curriculum. 



356 



