In summary, aerial application of the six potential DDT substitute 

 forest insecticides, with the exception of the field formulation of 

 Matacil, should not have a major toxic effect on brook trout and Atlantic 

 salmon. Marancik (1976) reported some inhibition of brain cholinesterase 

 in fish after aerial applications, but enzyme activity returned to normal 

 within 48 h. Nevertheless, all of the candidate insecticides, except 

 Orthene, may kill aquatic invertebrates. Results published by others 

 (e.g., Burdick eXat., 1960; Elson eXal., 1973; Flannagan, 1973) showed 

 that populations of stream invertebrates were markedly reduced after 

 aerial applications with forest insecticides other than DDT. Therefore, 

 field investigations are needed to determine whether any of the present 

 insecticides significantly depress aquatic invertebrate populations, and, 

 if so, the duration of the population depressions. The timing of such 

 effects on invertebrates may be critical with respect to adequate food 

 supplies for young salmon and trout. 



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Brauhn, J.L., and R.A. Schoettger. 19/5. Acquisition and culture of re- 

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Burdick, G.E., H.J. Dean, and E.J. Harris. 1960. The effect of sevin 

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Craighead, F.C. 1923. Relation between mortality of trees attacked by 

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Elson, P.F., A.L. Meister, J.W. Saunders, R.L. Saunders, J.B. Sprague, and 

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Flannagan, J.F. 1973. Field and laboratory studies on the effect of expo- 

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Haugen, G.N. 19/6. Effects on Sevin-4-0il and Dylox on small trout 



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