Oil sprays deposited on foliage and stems may penetrate and block the air openings of plants. Injury may result in darkened bark and the death of twigs and branches. Spotting may occur on the inside of thin bark. Applying excess amounts of oil or spraying at inappropriate times may result in russetted or water-soaked fruit skin and leaf burn.
Solutions
Oil burn can be minimized or even avoided if trees are not stressed in any way when sprayed. Lack of moisture, extreme temperatures, sudden change in temperature after spraying, prolonged winds, or poor conditions caused by disease or heavy pest infestation will predispose plants to phytotoxicity. Avoid spraying oil at temperatures above 90° F or below 30° F. Do not spray older-type dormant oils during the growing season.
