DESTRUCTION OF FLY LARVAE IN HORSE MANURE, 1915. 5 



The results obtained during 1914 with corn cockle (Agrostemma 

 giihago), a commercial extract of tobacco (Nicotiana tabacum) con- 

 taining 40 per cent nicotine sulphate, and stramonium (Datura stra- 

 monium) showed no marked or consistent larvicidal action, and these 

 substances were not tested during the past season. 



A few experiments with hellebore ( Veratrum viride, Veratrum album) 

 were carried out this year to supplement the results of the previous 

 season. The figures obtained both in the cage and open-pile experi- 

 ments confirm the statements previously made as to its effectiveness. 

 The results in Table 2 indicate that the hellebore infusion which had 

 been standing for 20 to 24 hours was more effective than the helle- 

 bore applied as a powder and immediately sprinkled with water. 



Two tests were made during the past season, using a 1 per cent 

 infusion of ground larkspur seeds (Delphinium sp.). An apparent 

 larvicidal action of 72 and 81 per cent was obtained. In view of the 

 cost and the comparatively low efficiency of this material it is hardly 

 to be considered a practical larvicide. 



An infusion prepared from the macerated roots of soapweed (Agave 

 lecheguilla) was again tested, but the results were practically negative. 



During 1915, 18 plant substances were tested, and a study of Tables 

 1 and 2 shows that Berberis, Cinchona, and quassia were the only 

 substances which gave indications of having any effect on fly larvae. 

 Berberis and Cinchona are both' expensive, and as apparently large 

 amounts of quassia are necessary to act as an effective larvicide none 

 of these three substances can be considered practicable. Black helle- 

 bore (Helleborus niger) was used in two experiments, but the results 

 were inconsistent. This plant is not only of a different genus but 

 belongs to a different family of plants than Veratrum viride and 

 Veratrum album. 



FERTILIZING MIXTURES. 



During the season of 1913 several tests were made with calcium 

 cyanamid, kainit, and acid phosphate, using each separately. The 

 results were such that no one of these substances could be considered 

 a good larvicide when used in reasonable amounts. As calcium 

 cyanamid and kainit showed some larvicidal action, and as the value 

 of using a fertilizer as a larvicide is obvious, experiments were started 

 during 1915 with the hope of rinding an effective fertilizer mixture. 

 In addition to the foregoing, gypsum, Chile saltpeter, and muriate of 

 potash were tried in mixtures. The results of these tests are sum- 

 marized in Tables 3, 4, 5, and 6. 



Chile Saltpeter (NaN0 3 ) and Acid Phosphate CaH 4 (P0 4 ) 2 , Ca 2 H 2 (P0 4 )2, 



Ca 3 (P0 4 ) 2 . 



A mixture of 2 pounds each of Chile saltpeter and acid phosphate 

 was used in duplicate cage experiments (Table 3, No. 3). The 

 results were poor, showing on the average about a 36 per cent larvici- 

 dal action. 



