Table VI. — Status of Infestation, Amherst, July 24, 1923. 



Treatment. 



Check 



Black Leaf "40", 1-100 

 Black Leaf "40", 1-250 

 Lead Arsenate, 3—50 



Eggs per 

 100 Plants. 



41 

 16 

 19 

 16 



Eggs already 

 Hatched. 



17 + 

 

 

 3 + 



The difference in the number of eggs found in the checks and in the treated 

 plots is greater here than at Littleton (see Table IV). This difference is 

 doubtless due to the greater force with which the spraj? stream is applied with 

 a power sprayer than with a compressed air sprayer. It seems clear that the 

 difference is due to the mechanical action of the spray stream in knocking eggs 

 from the plants rather than to any marked repellent qualities of the spray 

 materials themselves. Lead arsenate has not been demonstrated to be repellent 

 to insects, and yet no more eggs were found in the plot sprayed Avith this 

 material than in the plots treated with the nicotine sprays. In view of this 

 fact, it is impossible to attribute definite repellent qualities to the Black-leaf 

 " 40 ", in this connection. 



The numlier of larvae found compared with the number of eggs present, as 

 expressed in the last column of the table, indicates the toxic effect of the spray 

 materials. The counts in the check plots may be taken as a normal progression 

 of development of the eggs. The counts in the plot treated with lead arsenate 

 indicate a kill of about 50 per cent, while those in the plots treated with both 

 strengths of Black-leaf '' 40 " indicate 100 per cent control. 



The final count was made on August 20 and 21. The detailed results are 

 recorded in Table VII, and are summarized below. 



Average 832 221 73.5 



The high degree of effectiveness exhibited by Black-leaf " 40 " at the above 



dilutions is undoubtedly due to its ovicidal action, since, as shown in Tables 



VI and VII, eggs were found in the plots treated with these materials 



A 



