April, 11] HERRICK: CABBAGE APHIS 223 



plants before setting in the field. During the past season a series of 

 experiments in dipping seed-bed plants in various solutions was 

 carried out in response to these inquiries. 



A home-made fish-oil soap after the following formula devised by 

 Van Slyke and Urner was used with good results : 



Caustic soda 6 lbs., or 1 1-2 lbs. 



Water 1 1-2 gaJs., or 11-2 qts. 



Fish-oil 22 lbs., or 5 1-2 lbs. 



Simply dissolve the caustic soda in the water at ordinary tempera- 

 ture and when completely in solution add the fish-oil gradually, in 

 the meantime stirring the mixture vigorously. Complete and thorough 

 stirring while the oil is being slowly poured into the water and soda 

 is absolutely necessary. This gives a fish-oil soap at ordinary tem- 

 peratures that has no free alkali, is constant in water content, and a 

 very effective contact insecticide. 



Plants were dipped in solutions of this soap with the proportions 

 of 1 to 8, 1 to 10, and 1 to 15. The solutions of 1 to 8 were entirely 

 effective, killing every aphid hit. The weaker ones were not entirely 

 effective. 



No burning of the plants was induced so long as the plants were 

 dipped singly. In a series of experiments in- which many plants were 

 dipped in bunches of dozens and half-dozens and allowed to. lie until 

 set out and in some cases allowed to lie a half-hour in the sun, burning 

 was experienced in one case only. This was in the case of a bunch of 

 plants that had lain one half-hour in the sun with the roots protected. 

 The burning, however, affected only the outer leaves and the plants 

 recuperated very quickly. In the case of those plants which were 

 dipped in bunches some aphides always escaped being hit. 



A similar series of experiments was carried out with Leggett's 

 Anchor Brand of whale-oil soap. The solutions of 1 to 8 gave just 

 as good results as like solutions of the fish-oil soap. The weaker 

 solutions of 1 to 10 and 1 to 15 did not give as good results in killing 

 the aphis as Hke solutions of the fish-oil soap. This, perhaps, shows 

 a higher water content and consequent weaker solutions. 



Plants were also dipped in Black Leaf tobacco extract at the rate 

 of 1 to 100. All plants bore living aphides and no dead ones were 

 found. No injury to leaves. When plants were dipped in Black 

 Leaf 1 to 64 a few aphides were killed, but many were left alive. No 

 injury to plants resulted. 



These results should not be interpreted as showing that Black Leaf 

 will not kill the cabbage louse. As a matter of fact it is a very effec- 

 tive killing agent for this pest when applied with force, as we have 



