The other serious die-off of fish occurred in the Yellowstone River in 

 1955 [40]. In the fall, about 3 months after DDT was applied at 1 pound per 

 acre for control of the spruce budworm, large numbers of trout, whitefish and 

 suckers, including many or most of the young of the year, were found dead 

 along more than a 100-mile stretch of the stream. The loss of food organisms 

 may have been serious enough to have caused the death of the fish [ll]. 



During spruce-budworm control treatment of almost one million acres with 

 1 pound of DDT per acre on 3 national forests in Montana in 1956, numbers of 

 aquatic and terrestrial invertebrates were greatly reduced by the spray even 

 though maximum concentration of DDT in water samples was 0.33 parts per mil- 

 lion, one-half hour after spraying (Cope and Park, unpubl.; Graham and Scott, 

 unpubl.). A day later no measurable amount of DDT was present in the stream 

 samples. However, dead insects continued to be carried downstream for 5 days 

 and trout fed freely upon them, apparently without harm. A year later there 

 was a slight decrease in numbers of trout in 2 intensively studied streams, 

 but insect numbers were near normal and live trout appeared to be in good con- 

 dition despite the fact that analysis of their tissues showed that they con- 

 tained DDT. Eleven other streams in the sprayed area were studied less in- 

 tensively, with fish populations being studied in 5. In 2 of the latter there 

 were serious game-fish depletions - a decline of about lb% during the second 

 year after treatment. This indicates again that long-range effects may not be 

 apparent until the second year. 



The Fish-Pesticide Research Laboratory conducted field and laboratory 

 studies on fish exposed to a 1957 spruce budworm DDT treatment at 1 pound per 

 acre in the Yellowstone River drainage [lO]. In analysis of salmonids, it was 

 found that whitefish contained more DDT and DDE than did rainbow, cutthroat, 

 and brown trout. All fish collected had DDT in their bodies. Fish taken 85 

 miles downstream from the sprayed area were positive for DDT. The poison was 

 found in all fish at all seasons, and for more than 11 months after the spray. 



Studies were made on control of elm spanworm, Ennomos subsiqnarus , in 

 north Georgia in 1959. Aerial treatment of DDT, at the rate of 0.5 pound per 

 acre, resulted in substantial reduction of fish-food animals in a stream which 

 received the chemical. Another stream, avoided by the pilot, suffered no loss 

 of fish-food (Cope, unpubl.). 



B. Ornamental Tree Protection 



Shade tree insect and disease control can be serious. In Dutch elm 

 disease control, it has been estimated that the equivalent of over 2,000,000 

 acres has been treated [24]. Dosages in this type of treatment are from 2.5 to 

 5 pounds of DDT per tree; in areas where elms are numerous, dosages have been 

 as high as 17 pounds per acre. Numerous reports indicate that wildlife mor- 

 tality has occurred as a result of treatments for Dutch elm disease control. 



Bureau studies during 1959 were concentrated in Michigan and Wisconsin, 

 through research contracts with educational institutions. The Wisconsin 

 studies were conducted by Mr. L. Barrie Hunt under the direction of 



