April, '15] 



CORY: WOOLLY APHIS 



187 



to advise the use of the remedial measures generally recommended. 

 Two main lines of work have been followed, treatment of the soil with 

 ■dust applications and spraying the tops and soil about the roots. To- 

 bacco dust of various manufacturing companies and kerosene emul- 

 -sion have been the principal insecticides used. In addition, apterite 

 (a carbolic fertilizer), nicotine sulphate, fish oil soap and lime-sulphur 

 have been used. The usual mode of application in nurseries has been 

 to bar plow along each side of the row, apply the dust or spray and then 

 throw the earth back around the trees. 



Thus far we have been unable to secure good results wdth any of the 

 .above-mentioned insecticides. Kerosene has given better results 

 than any other insecticide. However, as this paper is concerned chiefly 

 with, results achieved in orchard work, the details of our experiments 

 on nursery stock will be left for another time. 



Treatment of Orchard Trees 



As in the nursery work the control experiments on Avoolly aphis 

 in orchards have been in progress for several years, without determinate 

 results. 



In the spring of 1912 work was begun in the orchard of E. W. Hun- 

 gerford, Marshall Hall, Md., in testing the value of various insecticides. 

 This orchard was selected because, first: it was badly infested with 

 woolly aphis and second because the soil in which it is set is a sandy 

 loam. As the soil in the college orchards is a clay loam, the sandy 

 soil conditions gave an opportunity for some comparisons. 



Eleven insecticides in the form of dust or liquids were applied in 

 trenches dug about the base of the trees. These trenches were dug 

 down deep enough to expose the main roots and about six feet in 

 diameter. All trees treated were infested with root aphis. 



Soluble oil, 1 to 15; Scalecide, 1 to 15; Electro Insecticide Soap, 1 

 pound to 4 gallons of water; Lemon oil, 1 to 24; Nico-Sul, 1 to 240; 

 lime-sulphur, 1 to 9; undiluted Pine Tar Creosote at the rate of If, 

 2 and 3 quarts per tree, kerosene emulsion, 10 per cent; tobacco dust, 

 IJ to 3 pounds per tree; One for All, J pound to 1 gallon and 

 Apterite 1 pound 3 ounces, 2 pounds 6 ounces and 4 pounds 12 ounces 

 per tree. As this was a private orchard, it was not considered ad- 

 visable to apply each insecticide to more than a few trees on account 

 of the danger of injury to the trees. It was planned to continue 

 the applications that held the most promise in the college orchards. 



The applications were made June 24 and 25, 1912. During the night 

 of the 24th rain fell and intermittent^ during the 25th so that the con- 

 ditions were exceptionally favorable for complete penetration. 



The trees were examined in the fall of 1912, without disclosing any 



