PART X — ENVIRONMENTAL CONTAMINANTS 



than many think) and we need selec- 

 tive use of pesticides to make the 

 best use of the ones we have. 



In developing modern pesticide 

 programs, we need to consider the 

 following: 



1. Complete control of the pest 

 is not essential or even desir- 

 able. Treatments can be re- 

 duced in number and dosage if 

 realistic economic-injury levels 

 are established; natural en- 

 emies are then left to dampen 

 resurgence tendencies and the 

 rise of secondary species, the 

 resistance problem is not ag- 

 gravated, and less toxic mate- 

 rial is added to the environ- 

 ment. 



2. The faunal elements in the 

 environment are interrelated. 

 The biologies and roles of 

 seemingly insignificant species 

 may be a clue to effective use 

 of a natural enemy against a 

 major pest. Thus, in winter, a 

 tydeid mite is a significant al- 

 ternate for an important preda- 

 tor of spider mites on grapes in 

 the San Joaquin Valley in Cali- 

 fornia; here, too, the non- 

 economic leafhopper Dikrella 

 cruentata found on wild black- 

 berries is essential to the over- 

 wintering of the effective para- 

 site of the grape leafhopper, 

 Erythroneura elegantida, a key 

 pest of this crop. Planting 

 of small patches of blackberries 

 near extensive vineyards can 

 thus provide the ingredient for 

 control of the pest species on 

 grapes, and the cessation of 

 treatments for this leafhopper 

 can result in the natural solu- 

 tion of the spider-mite problem 

 that the pesticides induce. 



3. Using the pesticide at the dos- 

 age and manner having the op- 

 timal effect in providing imme- 

 diate relief from damage but 

 causing a minimal ecological 

 disturbance may require a ma- 



terial having some persistence. 

 Short-lived alternatives to some 

 persistent materials may be 

 even more objectionable, and 

 more repeated applications may 

 be required, thus magnifying 

 the problems. 



4. If effective and practicable pes- 

 ticides should be used in spe- 

 cific parts of the environment 

 rather than as general coverage 

 materials. 



5. Each pesticide should be ap- 

 praised separately and on the 

 basis of specific use unless, as 

 seems the case for DDT, the 

 general severity of the pollutive 

 accumulation in the environ- 

 ment justifies its demise (aside 

 from public health use in 

 heavily malarial areas, etc.). 



6. Natural enemies, cultural meas- 

 ures, traps, and other feasible 

 nonpollutive measures should 

 take priority over use of pes- 

 ticides, with the latter used 

 to supplement them. Cultural 

 measures may include growing 

 of trap crops or ones harboring 

 alternate hosts of enemies, de- 

 struction of pest-harboring ref- 

 uges, use of planting dates, etc. 

 Releases of sterile insects or 

 use of genetic techniques should 

 be tried when promising for 

 a particularly difficult species, 

 where its solution would open 

 up avenues for better-integrated 

 control of the pest complex. 

 Releases of the pest itself, use 

 of strategic repetitive releases 

 of natural enemies, augmenting 

 techniques, and introductions 

 of new natural enemies should 

 be especially explored in depth. 

 It is a fallacy to think that, 

 since crops are highly artifi- 

 cial (unnatural) and grown as 

 simple monocultures, the laws 

 governing the balance of nature 

 and the role of natural enemies 

 are insignificant here. Complex 

 natural communities present a 

 more stable picture than sim- 



pler communities because of 

 the greater diversity in trophic 

 links. Yet many of the species 

 of natural enemies accounting 

 for the low numbers of a po- 

 tentially disturbing (to the 

 community) phytophagous in- 

 sect are highly host-specific. 

 Such links (host and host- 

 specific enemy) are often trans- 

 ferred to crop situations. Some- 

 times the pest form has arrived 

 without the natural enemy. 

 Our best examples of biological 

 control have resulted from our 

 seeking out and introducing 

 such natural enemies. 



Integrated control, a systems- 

 analysis approach, can be built on 

 the basis given above. The computer 

 is essential in systematizing informa- 

 tion and testing hypotheses of how 

 complex systems work so as to ar- 

 rive at proper manipulating strate- 

 gies, but it cannot substitute for 

 grass-roots information. Much grass- 

 roots input is needed before any 

 major complex case (crop) can be put 

 on a rational, predictable scheme of 

 management. Key natural enemies 

 commonly present a high degree of 

 predictability for certain major pests 

 (and others can be developed), thus 

 making it possible to develop the sys- 

 tem around such a central fact when 

 established. Moreover, we must go 

 on with the task of working out con- 

 trols while we are gaining additional 

 insights for a full systems-analysis 

 approach. In-depth study of faunal 

 relationships and crop phenology, 

 economic-injury levels, and the like 

 are musts. 



For an integrated control scheme to 

 be fully effective in achieving the 

 goal described, a revolution in the 

 system of pest-control advisement is 

 essential, and this cannot be accom- 

 plished without massive training and 

 re-training of a corps of pest-control 

 ecologists (see below). 



Moreover, the whole social, eco- 

 nomic, and cultural situation relative 

 to insects or insect parts in foods, as 



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