CHRYSANTHEMUM MIDGE. 



19 



successfully and continually. Hence, it was decided to test out 

 . the efficiency of several applications when made two and three days 

 apart. The test is given in the next paragraph. 



EXPERIMENT 2. 



In the treated lots five plants were used for (a), (b), (e), and (f), 

 and six plants for (c) and (d) for each test. The plants used had 

 been growing in pots. Only two plants were used in both checks. 

 The dipping was done as indicated every two or three days. Obser- 

 vations were taken daily. 



Table VI. — Results of experiment 2. 













Percent- 





Started. 



Closed. 



Treatment. 



Total 

 emerged. 



Total 

 killed. 



age of 

 effi- 

 ciency. 



Pvemarks and conclusions. 



1919. 















(a) May 1 . . . 



May 10. . 



Nicotine sulphate (1-500), 

 fish-oil soap 1 ounce to 

 1 gallon. 



217 



123 



56.6 



Greatest efficiency with- 

 in 24 hours of treat- 

 ment. 



(b)May 1... 



May 10.. 



Nicotine sulphate (1-800), 

 fish-oil soap 1 ounce to 

 1 gallon. 



Nicotine sulphate (1-1,000), 



152 



86 



56.5 



Same as above. 



(c) May 19. . 



May 23.. 



45 



30 



63.6 



Lower leaves turned yel- 







fish-oil soap 1 ounce to 1 









low and died on most 







gallon. 









plants. 



(d) May 19. . 



May 23.. 



Volatile nicotine sulphate 

 (1-1,000), fish-oil soap 1 

 ounce to 1 gallon. 



72 



35 



48.6 



Slight blackening of tips 

 on larger leaves. 



(e) May 1.. . 



May 10.. 



Linseed-oil emulsion plus 

 nicotine sulphate(l-800) . 



80 



2 



2.5 



Not efficient. 



(f)May7.... 



May 9. . . 



Fish-oil soap 1 ounce to 1 

 gallon. 



Many. 











All emerged successfully; 

 not efficient. 



(g) May 1 . . . 



May 10. . 



Check 



Many. 











All emerged successfully. 



(h) May 19. . 



May 23. . 



Check 



Many. 











Same as above. 



Discussion of results. — The data represented in Tabic VI are 

 self-explanatory as to the relative value of the various strengths 

 and combinations of insecticides. The mathematical representation 

 of the first two lots does not clearly define the actual state of affairs. 

 It was repeatedly observed that on the day following treatment the 

 number of adults killed was usually larger than on the second or 

 third day. In other words, the effectiveness of such practices de- 

 pends entirely on the interval which elapses between applications, 

 and the conclusion to be drawn is that nightly or daily applications 

 are absolutely necessary to get the maximum killing. The insecti- 

 cide proved to be effective in killing the adult in the act of emer- 

 gence, but did not sufficiently penetrate the tissues of the leaves to 

 kill the immature stages within the galls. The column "Total 

 killed" is understood to mean the killing of the adult\in the process 

 of emergence (PL II, B). It is also important that the treatment 

 should be applied when the adults are almost ready to emerge from 

 the galls. 



