6 BULLETIN 165, U. S. DEPARTMENT OF AGRICULTURE. 
and in these experiments is used at the rate of 1-2,000. The nico- 
tine sulphate used was standardized to 40 per cent and the solution 
of quassiin was used so that it would correspond with the 40 per cent 
solution of nicotine sulphate. For instance, instead of using 1 gram 
of quassiin to 2,000 cubic centimeters of water, 0.4 gram was used 
to 2,000 cubic centimeters of water. 
During the early part of the work it was discovered that the whale- 
oil soap, even when used at the greatest dilution at which it had any 
spreading effect (1 pound to 100 gallons), killed a certain percentage 
of the aphides. Since a spreader is necessary, experiments were 
inaugurated to find one that would have no effect upon the insects 
treated. It was found that the soap bark solution which was being 
used in some other work was an excellent spreader and did not affect 
the insects in the least. In all of the following experiments a water 
decoction of this material was used at the rate of 2 pounds of soap: 
bark to 100 gallons of water. 
In applying the solutions, a compressed-air spray machine (fig. 
1) which maintained 50 pounds pressure and handled as small an 
amount as 200 cubic centimeters was used. A fine mist nozzle was 
so adjusted to this pressure of 50 pounds that a washing rather than 
a mist spray was produced. 
In conducting the experiments detailed in Table II prune twigs 
infested by the hop aphis (Phorodon humuli Schrank) and the prune 
aphis ([Zyalopterus pruni Fab.) were brought from the field and, 
after being sprayed with the solutions, were set in moist sand. 
By placing the pots of sand containing the sprayed twigs on sheets 
of paper the percentage of the insects that were killed by the solu- 
tions were readily obtained. Check twigs were kept to make sure 
that there was not a marked mortality fon some other cause. 
Table IT gives the results of the spraying experiments with quassiin 
in aqueous solution and also in solutions of certain alkaline sub- 
stances. 
TaBLeE I1.—Aesults of experiments with quassiin as a contact insecticide. 
SERIES NO.1. WITH SOAP BARK IN LABORATORY. 
Number of} Per cent of 
Formula. aphides aphides 
sprayed. killed. 
OPA. STATS Ot O00; COs ae oat esay eo ees or arcs See ee otra 904 83. 1 
O:4-eraims io 22000 Gre 2 Ais Sot) Se Ree es ee ine ek ra ee ae oe Seen crete | 8, 060 93.02 
O:4 eramsntod:SO00Cry. fe. ease Sot Se ee eee at be ee eee ee oled ae | 1,119 94.6 
O42 sramsitoulH500iCGH a tess i ee a ee ee eee oe oe eee 1,310 93.9 
OA Sramsilo OOO CGH e-store nee Se Saat eee ee a Al 1, 831 99.7 
SERIES NO.2. WITH WHALE-OfFL SOAP IN FIELD. 
Oras orams) tO: 000jiCCst asc kee ees ee ty ee ee ee ere cond en ee ee 1,776 99. 4 
O:-Aorams' tod’ S00iCG ee Lok eee ais GE es a peer Baie MURAD Mp es Be oes eet cae 3,197 99.8 
Orajerams! tot S00! COs: ke ee ee ee ae ee a 3,546 99.8 
