Airplane Dusting in Control of Malaria Mosquitoes 9 



In the cotton-dusting work the best time for making the appli- 

 cations was foimd to be immediately after daylight when the air is 

 usually still and the plants covered with dew. In the lake dusting, 

 however, the presence of dew was a decided disadvantage, since it 

 caught and held the dust particles, and this more than offset the 

 advantage of flying early in the morning to avoid the more irregular 

 air conditions encountered later. 



The general results of the lake-dusting experiments in 1923 are 

 summarized in Table 2. 



Table 2. — Results of lake-dusting experiments 1 for destruction of larvce of 

 malaria mosquitoes, Hound, La., 1923 



FIELD LAKE 



Date 



h Average 



Number number of 



stations larvae Per 

 10 dips 



Average Number of 



number of stations Reduc- 



poison j with 50 i tion for 



granules '' per cent j entire 



per square or higher 

 inch mortality 





1923 













Per cent 



Aug. 13.- 







10 



35.0 1 



16 





67.7 



15 







10 





9.7 I 



27 





93.0 







1 



10 



8 





10.7 --- 





3 



1 

 10 



34.6 



22 



13.0 .. 









29 



10 / 

 10 \ 



20.0 



133 



93.5 





\ 



9.6 



163 



9 



87.5 



Sept. 12 





< 



io r 



10 \ 



14.7 

 14.4 i 



24 

 38 



4 

 7 



15.6 

 54.9 



20 





{ 



10 / 



20.0 



84 



9 



84.0 







10 



\ 



18.0 ... 





8 



88.4 



ALGODOX LAKE 



Sept. 5 



10 -- -- 



21 



26 



10 



6 



6 



6 



20.5 

 14.3 

 21.3 

 22.7 



4 

 33 

 120 

 99 



2 

 3 



3 



4 



0.1 

 14.4 

 18.8 

 47.1 



TEXAS FIELD LAKE 



Sept. 14 - 



25 



,. 



13 



15.7 

 34.8 



39 

 122 



2 

 7 



1.9 

 47.1 



WALNUT BAYOU 



Sept. 28 - 



HI 



11.4 



156 



9 



78.1 



1 The mixtures used contained from 10 to 50 per cent of Paris green. 



On Algodon Lake, the second area selected, conditions for dust- 

 ing were very difficult, in that the breeding area consisted of a long, 

 narrow strip of water in the midst of a particularly heavy growth 

 of tall willows and buttonbush trees, and without any open space to 

 serve as a guide mark for the pilots. The debris and aquatic growth 

 on the water itself were also unusually thick, and an extra quantity 

 of poison was required for effective results. In none of the four 

 trials at this place were the applications particularly successful, but 

 in three of the four the average quantity of arsenic found on the 

 plates would ordinarilv have been considered sufficient. This also 



