Growers also take care to maintain good agitation in the spray tank and check to make certain that the oil emulsifies. These applications were timed to prevent the development of codling moth eggs by essentially smothering them with the oil. Foliar oil sprays have provided control of other pests as well. Leafrollers have been suppressed with oil applications aimed at codling moth. Oil is thought to be effective against the egg stage, although effects on larvae or even adult behavior are possible.
Optimum timing appears to be when fifth instar nymphs appear.
There is work to show that oil is quite effective in controlling tentiform leafminer , when applied at the pink stage of apple bud development after egg laying has begun. Summer oil applications for mite control provided good knockdown of European red mite but also reduced populations of the predatory mite, T. occidentalis . Foliar oil applications have been studied for the control of powdery mildew on apples. Research in Washington in 1995 focused on establishing the limits of oil applications on apples and pears. Codling moth work will compare two versus three oil sprays per generation, timed prior to egg hatch.