Only apply oil if temperatures remain above freezing (ideally above 40☏) for 24 hours after application. peach/nectarine: pre-bloom (when the pink shows through the bud).apple: half-inch green (ideally, application is made at green tip stage).The last point at which you can safely apply oil is: The window for application extends from bud swell to when leaves just start emerging. There are a few factors that must coincide to determine when to spray: the bud stages of your fruit trees ( pictures of fruit bud stages), and temperature. Oil should be applied at a rate of 2%, which is 5 Tbs in 1 gallon of water.Make sure you thoroughly cover all cracks and crevices.When spraying apple trees, add in copper for fire blight.Mix oil with an insecticide such as Warrior or Asana.Oil should be applied at a rate of 2%, which is 2 gallons per 100 gallons of water.In northern Utah, it is approaching time to apply the spray in some areas. In southern Utah, dormant oil should already have been applied. This coincides with the increasing activity of the overwintering insect, such as aphid eggs, scale nymphs, and peach twig borer larvae. A better term would be a “delayed-dormant” application, because the oil should be applied after bud swell. Spray all surfaces of the orchard (including trellis posts and other inter-mingled tree crops) as a high volume spray.ĭespite the fact that we call it “dormant oil”, the timing of a horticultural oil spray is not when trees are still dormant. The primary purpose of this treatment is to help reduce the bacteria on the orchard surfaces. It is OK to mix with 2% oil for the insect treatment. In years when weather conditions are very conducive to fire blight development, it can be difficult if not impossible to control the disease.For fire blight, apply copper to apple/pear between swollen bud and green tip stages. Sprays prevent new infections but won’t eliminate wood infections these must be pruned out. (See Removing Diseased Wood.) If fire blight has been a problem in the past, apply blossom sprays. Monitor trees regularly, and remove and destroy fire blight infections. Trees shouldn’t be irrigated during bloom. The succulent tissue of rapidly growing trees is especially vulnerable thus excess nitrogen fertilization and heavy pruning, which promote such growth, should be avoided. When temperatures of 75° to 85☏ are accompanied by intermittent rain or hail, conditions are ideal for disease development. Fire blight development is influenced primarily by seasonal weather. The amount of fruit loss depends upon the extent and severity of the disease. However, most cankers are small and inconspicuous thus infections might not be noticed until later in spring when flowers, shoots, and/or young fruit shrivel and blacken. The ooze turns dark after exposure to air, leaving streaks on branches or trunks. The first sign is a watery, light tan bacterial ooze that exudes from cankers (small to large areas of dead bark that the pathogen killed during previous seasons) on branches, twigs, or trunks. In spring, branch and trunk canker symptoms can appear as soon as trees begin active growth. Fire blight, caused by the bacterium Erwinia amylovora, is a common and frequently destructive disease of pome fruit trees and related plants.
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