^ 1 6 Journal of Agricultural Research voi. x, no. io 



(b) Effectiveness of Spray Solutions Applied Outside the Laboratory 



In the experiments described under this heading various plants, all 

 badly infested with aphids, were sprayed eariy in the morning with a 

 hand sprayer, and the following morning the number of aphids killed was 

 .estimated. Reference to Table IX shows the following: Formula 3 A, 

 the one used by Parker (32) on the hop aphis, was efficient upon only 

 Aphis rumicis, but killed 95 per cent of the aphids on the ragweed and 

 asters. Formula 6B (first extract) was efficient upon the aphids on the 

 ragweed and asters, but killed only 95 per cent of the pea aphids, Aphis 

 sp., and rose aphids tested; the second extract of the same chips was not 

 efficient upon any of these aphids. Formula 7 was efficient upon all the 

 aphids tested, but the quantity of chips employed is so great that the 

 formula could not be used economically for practical spraying. Not 

 one of those formulas, even including nicotine sulphate (i: 1,200 of soap 

 solution) was efficient upon Myzus persicae on the eggplant. 



(c) Comparative Rapidity of Action of Quassia Extract and Nicotine 



Sulphate 



Since formula 6B (first extract, Table IX) is somewhat less expensive 

 (excluding the labor of preparing it) than nicotine sulphate (1:800 of 

 soap solution), and, as its efficiency 24 hours after its application is com- 

 parable to that of the nicotine-sulphate solution, the following experi- 

 ments were performed in the laboratory to determine the rapidity of the 

 action of these two insecticides, so that the effects of a shower upon 

 aphids sprayed v/ith these two solutions might be deduced. In each 

 individual experiment the aphids were first sprayed with one or the 

 other insecticide and then with tap water after one of the intervals 

 of 5, 10, 20, 30, 60, or 120 minutes. The following plants and aphids 

 were used: Kale leaves bearing 180 to 425 aphids; rose branches bearing 

 22 to 115 aphids; nasturtium leaves bearing 89 to 107 aphids; and 

 bladder-senna branches bearing 36 to 92 aphids. 



Twenty-four hours after applying formula 6B, the following aphids 

 were dead: None of those sprayed with tap water after 5, 10, and 20 

 minute intervals ; a few nasturtium aphids sprayed with tap water after 

 a 30-minute interval; a few of those on the kale leaf and bladder-senna 

 branch and about one-half of those on the nasturtium leaf sprayed with 

 tap water after a 60-minute interval ; most of those on the kale leaf and 

 bladder-senna branch, practically all on the nasturtium leaf, but only a 

 few of the rose aphids sprayed with tap water after an interval of 120 

 minutes. All the aphids on a kale leaf sprayed with this formula, but 

 not later with tap water, were dead 6 hours after being sprayed; all of 

 , those on another leaf sprayed with the nicotine-sulphate solution, but 

 not later with tap water, were dead 2 hours after being sprayed. 



