Experiments with Tar Distillate Sprays Against Fruit Aphids and Associated Insects

Abstract

Field trials of tar distillate sprays were conducted in a number of orchards in western New York during 1932 to determine their effects on the trees and efficiency in controlling rosy apple aphid, black cherry aphid, San Jose scale, oyster-shell scale, eye-spotted bud moth, apple red bug, and pear psylla. Four American and four European brands were used in the experiments. Concentration of tar washes in the applications on apples generally varied from 5 to 7½ per cent, altho mixtures containing 2 and 3 per cent were tried on a few trees. Except in the case of one plat that was sprayed very late in the fall, all applications on the apple were made in the spring not later than the gray-tip stage of the buds. On sweet cherry and pear, the mixtures contained 4 and 5 per cent of the emulsions respectively. Control of the rosy apple aphid was secured in all trials when the concentrations of tar washes were not less than 5 per cent. Lower concentrations generally proved less effective. A fall application did not give as high control as spring treatments. In practically all instances, the control of rosy apple aphid by spring applications of tar washes (not less than 5 per cent) was similar to that effected by nicotine sulfate (1- 800). A single experiment indicates that these materials may prove effective against the black cherry aphid. Tests with one brand indicate that in severe infestations, tar distillate sprays are not as effective as lubricating oil emulsions for the control of San Jose scale. Four brands, used at 5 and 7½ per cent, appear to be very effective on oyster-shell scale. Tar washes (7½ per cent) in the tests were but slightly inferior to nicotine sulfate (1-400) in lubricating oil against the eye-spotted bud moth, while lower concentrations of the washes produced moderate control. The results with apple red bug indicate that rather low efficiencies are to be expected from tar washes (7½ per cent) when used against this insect. One brand (5 per cent) proved destructive to the eggs of pear psylla. At the concentrations used none of the materials proved injurious to the buds or wood of apple, sweet cherry and pear during 1932.