Spraying Oil is a thick white emulsion of petroleum distillates and surfactants which readily mixes with water. It is recommended for the control of red spider mites, mealy bugs and scale insects, pests which are usually difficult to control.
Spraying Oil works on red spider mites by both blocking their breathing pores and by making the leaf surfaces inhospitable to migrating mites. Scale insects and mealy bugs cannot tolerate the penetrating solvent and surfactant properties of Spraying Oil and they will not attach themselves to, or invade treated leaf surfaces.

Spider mites are pests of conifers and leylandi in the UK. Mites feed externally on conifer tree needles with piercing-sucking mouthparts that puncture the plant tissue and suck out the liquid within the cells. In light infestations the foliage will appear to be speckled with very tiny yellowish-green spots. If the population of mites increases the damage can become severe enough to turn the foliage entirely greenish-yellow and eventually brown. Heavily infested branches will drop their needles. Close examination of infested foliage may reveal very fine webbing on the stems at the base of the needles.

Spider mites are tiny and difficult to see with the naked eye on the plant. A convenient detection technique is to hold a sheet of white paper under a branch and then shake or tap the branch against the paper. The mites, if present, will show up as tiny, slow-moving specks on the paper.