EFFECTS OF DDT AND OTHER INSECTICIDES 



15 



DDT in emulsion appeared to be 

 more toxic than in a solution of 

 the same concentration in kero- 

 sene. 



The spraying- of oyster shells 

 with a 5-percent solution of DDT 

 in kerosene at the rate of 1 pound 

 to an acre did not interfere with 

 the setting of oysters. Spraying 

 the same solution at the rate of 3 

 or 5 pounds of DDT to an acre, 

 however, may somewhat affect 

 the intensity of setting, although 

 this was not clearly shown in the 

 experiments. 



The spraying of oyster beds 

 with DDT solution or emulsion at 

 the rate of li/^ pounds of DDT to 

 an acre caused no unusual mor- 

 tality among adult or young oys- 

 ters. Beds sprayed with DDT 

 emulsion usually showed a lighter 

 set than did the untreated control 

 beds or beds sprayed with a 5-per- 

 cent DDT solution in kerosene. 



DDT-painted vertical concrete 

 collectors had somewhat fewer 

 oysters than the kerosene-painted 

 collectors or those in the un- 

 treated control beds. Untreated 

 controls collected the largest num- 

 ber of spat. 



No significant difference was 

 found in the average size of oys- 

 ters on the untreated and the 

 DDT-treated collectors. 



The dipping of adult oysters in 

 a 5-percent solution of DDT and 

 kerosene resulted in the same rate 

 of mortality as that of oysters 

 dipped in kerosene without DDT. 

 It did not significantly affect their 

 rate of growth or increase in 

 weight. 



The shell movement of oysters 

 kept in aquaria to which a 5-per- 

 cent solution of DDT was added 

 in quantities of approximately 5 

 pounds of DDT to an acre was not 

 different from that of control 

 oysters. No mortality was ob- 

 served during exposure ranging 

 from about 5 to 8 days and for 6 

 weeks after exposure. 



Oysters kept in a concentration 

 of one or two parts of DDT in 

 emulsion per million parts of 

 water, although showing abnor- 

 mal shell movements, survived 

 periods of exposure ranging from 

 about 5 to 8^2 days. It is doubt- 

 ful^ therefore, that sufficient con- 

 centrations created under natural 

 conditions for comparatively short 

 periods would seriously affect 

 adult oysters. 



The treatment of oyster shells 

 with a solution or emulsion of 

 DDT virtually prevented the set- 

 ting of barnacles. 



CHRONIC TOXICITY TO QUAIL OF 

 NEW INSECTICIDES 



Several new insecticides were 

 tested at the Patuxent Research 

 Refuge for their chronic effect on 

 quail. For these tests, four floor- 

 less brooder coops each having a 

 base area of 46.7 square feet were 

 used to confine groups of 20 quail 

 (10 males and 10 females). In the 

 first test, the effects of spraying the 

 habitat were studied. Wettable 

 mixtures of DDT, DDD (dichloro- 

 diphenyldichloroethane) , benzene 

 hexachloride, and chlorinated 

 camphene were applied to the veg- 

 etation in the pens, one mixture to 



