For the dormant oil application, the petroleum-based oils work the best, although canola-based oil is another option. There are plant-based oils and petroleum-based oils.Oil is sold as a concentrate, so it must be mixed at the proper rate with water before application.Make sure you thoroughly cover all cracks and crevices of the bark and buds.When spraying apple or pear trees, it is OK to also mix in the proper rate of copper to help prevent fire blight bacteria from multiplying.If you are not growing organically, and aphids or scale have been a serious problem and oil alone has not worked in past years, consider mixing the oil with the appropriate rate of an insecticide, such as Spectracide Triazicide, GardenTech Sevin, or Malathion.Oil should be applied at a rate of 2%, which is 5 Tbs in 1 gallon of water.Thoroughly cover all cracks and crevices of the tree bark and buds.When spraying apple or pear trees, it is OK to mix in copper for fire blight.

( Optional) Mix oil with an insecticide such as Warrior or Asana to help improve knockdown of overwintering pests.Oil should be applied at a rate of 2-3%, which is 2-3 gallons per 100 gallons of water.This will help give the oil time to work. Do not apply if rain is predicted within 24 hours.Ideally, oil should be applied on a clear, non-windy day in the 50° to 70☏ temperature range.Only apply oil if temperatures remain above freezing (ideally above 40☏) for 24 hours after application.peach/nectarine: just before first bloom (when the pink shows through the flower bud).apple: half-inch green (ideally, application is made at green tip stage).The last point at which you can safely apply oil (at the recommended rate below) for each crop is: The window for application extends from bud swell to when leaves start emerging, usually a period of several weeks, depending on the tree. There are two factors to consider for determining when to spray: the bud stage of your fruit trees ( pictures of fruit bud stages), and weather conditions. If your fruit trees are not affected by the pests in the image gallery shown below, you can skip the oil application. But in northern Utah, it is time to apply the spray if not done already. In the warmest areas of Utah, trees are blooming or past bloom, so the oil may already have been applied. If applied too early, the oil will not work as well on these insects. This timing matches up with the increasing activity of the overwintering insect stages, such as aphid eggs, scale nymphs, and peach twig borer larvae. In other words, the oil should be applied around bud swell or later.

You are likely familiar with the term, “dormant oil,” but the application is applied after trees break dormancy (but before bloom). The use of horticultural oil before bloom can target many insect pests (see images below, and see more explanation about oil below under “Backyard”).

Pear blight