For example, a 400 gallon equivalent tree will be sprayed dilute with roughly 240 gallons of water at tight cluster. If you must spray with a concentrate sprayer, concentrate no more than 2X. Remember, the more water, the better efficacy you will have. Oils are highly refined petroleum products and, as such, will have some compatibility problems. If applied closer than 14 days, phytotoxicity can occur, with symptoms such as leaf tip burn showing up on trees. Many fungicides are compatible with oil, such as Nova, Rubigan, EBDCs, and others.
Temperature also plays a role in the safety of oil sprays to the tree.
This makes it difficult to apply oils under typical Michigan conditions. Overall, an oil spray that is properly timed is one of the most important insecticide applications you will make all year. Often, insect and mite populations are controlled well enough with this spray that later aphid, scale, and mite control can be reduced or eliminated.