30 SEVENTEENTH Report STATE ENTOMOLOGIST OF MINNESOTA—1918 
TABLE IV 
Material Per cent killed 
Dist. Parker’s Tap 
water L. water water 
IN GievoliyihaaXen(o} (echtcmiaetaess ecioeeionac nics eitoe aero 75 74 50 
Nicofume oleate and soap 1 lb. to 50 gal. ..... 96 100 97 
Nicofume oleate with 1% kerosene emulsi- 
fT Cetneeera te crace meh Hoe eae ee 67 73 59 
mN COMM ney so coca olga ie eae ache ache soteecake ous 48 61 715) 
“Nicofume” and soap 1 Ib. to 50 gal......... 100 100 96 
SNicotume: and» soap lialb, to 100 gala. -.. -- 80 91 79 
lake ean, 4 0ee en soree inn Acca esata tetey nents 58 4] 48 
“Black leaf 40” and soap 1 lb. to 100 gal...... 99 er a 
“Black leaf 40” and soap 1 lb. to 50 gal....... 100 96 100 
From these results it would appear that both nicofume and black 
leaf 40 with soap are effective in killing leaf hoppers, but it is also 
evident that the insects must be thoroly wet with the spray if the 
results are to be most effective. The fact that such a small proportion 
of the leaf hoppers was killed in the field experiments was probably due 
to the fact that many of the insects were not hit. Altho three 
nozzles were used to each row, the under side of the leaves was not 
at all thoroly wet. Thus the fault would seem to lie with the mechanics 
of application rather than with the insecticide. 
From observations in the field and in the laboratory the amount of 
nicotine necessary to kill a leaf hopper in either nymphal or adult 
stages, is certainly not greater than that required to kill the potato 
aphis, since individual aphids accidentally included in experiments 
have frequently come through alive, while the leaf hoppers subjected 
to the same treatment have all been dead. It seems almost certain, 
therefore, that if a tobacco extract with soap can be applied in such a 
way as to wet the leaf hoppers thoroly it will be effective in 
destroying these insects. Soap, however, seems essential to the suc- 
cessful use of these materials, giving the spray liquid the proper 
physical characteristics for maximum effectiveness,* as well as adding 
a toxic action of its own. For maximum effectiveness, this would 
necessitate the separate application of the contact insecticide, or its 
application in mixture with other materials not of a strongly alkaline 
nature, since a strong alkali would destroy the soap, thus reducing the 
value of the tobacco extract. This would preclude the use of these 
extracts with bordeaux mixture. On the other hand, they could be used 
with lead arsenate, paris green, or zinc arsenite; since the soap solution 
would not be destroyed by these compounds. The addition of soap 
3 Moore, Wm. and Graham, S. A.— Physical Properties Governing the Efficacy 
of Contact Insecticides. Jour. of Agric. Res. Vol. XIII No. 11, June 1918. 
