Page:The Olive Its Culture in Theory and Practice.djvu/155

Rh when diluted with water, are nevertheless too much weakened for effective use against scale insects. The reason that high fire test kerosene is recommended as an insecticide is, that the lighter oils with which it is associated in a crude state, have been eliminated by the refining process, these being exceedingly deadly to vegetation, leaving the refined kerosene which should always be used for this purpose. The heat of the sun increases to an injurious extent the action of kerosene, and stronger solutions than that above given if used at all, should be applied on cloudy days or in the evening. Experiments with different grades of refined oil, the Elaine amongst the number, show that they all emulsify equally well if the alkali contained in the soap is of sufficient strength. But the Elaine separates the soonest. The kerosene wash should be applied in a fine spray from the center of the trees, and not the least of its recommendations will be its very great economy. In addition to insect pests and vegetable parasites, the olive tree numbers among its enemies the blackbird, the robin, the starling, the jay, and the crow, as they are all eager devourers of its fruit, but it is aided and greatly assisted by the nightingale, the titmouse or tomtit, and the woodpecker, as they never touch the berries, and are insect eaters only, and should therefore be encouraged in the orchard. The predatory birds should be fired at in the air, so as not to wound the trees with the shot. The pugnacious English sparrow, by driving away all other birds, especially the little tomtit, is an enemy particularly to be marked for destruction.