78 JOURNAJ. OF ECONOMIC ENTOMOLOGY [Vol. 12- 



strength that was effective was again found to be 1-500. When I 

 figured the expense of these two combinations there was such a Uttle 

 difference in favor of the new mixture that I gave up the idea of trying 

 to get our farmers to use it. 



Now I am going to emphasize thoroughness first, and sprays no 

 stronger than known to be satisfactory if they are appHed thoroughly. 

 If we can trust kerosene emulsion in the hands of farmers it will help 

 solve the cost of repeated spraying to control potato aphis. 



Mr. E. N. Cory: I want to give our experience in regard to the 

 strength of Black-Leaf 40 that is required. Where we supervised work 

 we were able to get results with Black-Leaf 40 at the rate of 1 part to 

 800 parts of water, but the farmers did not get results by using this 

 strength. They doubled the amount of Black-Leaf 40 and in many 

 cases secured excellent results. To them it was simply a problem of 

 getting control, rather than a matter of cost, as they were growing 

 tomatoes under contract and the price was excellent. Many of them 

 stated it was not a question of the cost of the insecticide, but a question 

 of killing the lice. 



I would like to ask in regard to the effect last year of parasites and 

 lady-beetles in destroying aphids. We found that toward the end of 

 the infestation, or in fact at the height of infestation, the lady-beetles 

 were doing excellent work and this was a question in the mind of many 

 farmers as to whether parasites were not effective in control rather 

 than spraying. 



Mr. C. p. Gillette: I have done a good deal of work in con- 

 troUing plant lice in Colorado, and have found that if the application 

 does not kill, it is because the body of the aphid is not thoroughly wet 

 with the insecticide. I once gave a student some Black-Leaf 40 for 

 use in killing the black chrysanthemum aphids in the greenhouse. 

 He reported that he could not kill them with any strength that he 

 used. I made a test and found that I could not kill this aphid, but if 

 soap was added to the water good results were secured. If it was not 

 used very little of the spray would remain on the bodies of the aphids. 

 One part of Black-Leaf 40 to 1,000 parts of water is sufficient to kill 

 them, if their bodies are thoroughly wet. 



Mr. T. J. Headlee: Our experience with vegetable plant lice 

 during the past season has raised the following questions: (1) Is it 

 possible in all the species attacking vegetables to discover the infesta- 

 tion while the plants are yet small before they have had a chance to 

 assume a recumbent habit and by a single thorough treatment of any 

 of these crops bring the aphis under control? (2) What sort of appa- 

 ratus must be used, what sort of formula, what pressure and how many 

 gallons must be used on an acre? 



