Insecticides on Shade Trees and Ornamentals

Abstract

A series of tests were conducted to determine tolerance of various trees and shrubs to dormant oil sprays. At Stamford, Connecticut, the sugar maple, black walnut, butternut and beech were found to be very susceptible to oil injury, and certain conifers, particularly the spruces, were apt to be injured where excessive amounts were used. The other trees and shrubs sprayed with various oils at dormant strength were not injured by the application. Dormant oil 1-16 was very effective in killing the overwintering young of the tulip tree scale, Toumeyella liriodendri. The white pine bark aphid, Adelges pinicorticis, was very satisfactorily controlled with a dormant oil at 1–25. 1–50 and 1–50 to which was added nicotine sulfate (40%) 1–800. Tests of several commercial sprays applied to spruce branches and the latter then immediately covered with paraffin bags resulted in no appreciable injury, indicating that high humidity was probably not an important factor in causing injury. A lead oleate, coated arsenate of lead applied to twigs upon which feeding hickory bark beetles, Scolytus quadrispinosus were confined resulted in appreciably more killing than in the case of others sprayed with ordinary arsenate of lead. A spray of 2% summer oil plus nicotine sulfate 1–800 and a commercial vegetable oil, soap, nicotine sulfate mixture diluted 1–10 gave practically 100% kill of young juniper scale, Diaspis carueli, in midsummer. A very satisfactory control, 95–100%, was secured in the case of a number of insects by spraying with the vegetable oil, soap, nicotine spray.