Aphids

Aphids over-winter on buds on most fruit.

Question: Is it time yet to spray dormant oil?

Answer: It’s still too early for dormant oil spray. However, horticultural oil sprays are an important part of a good pest management program. An oil spray applied at the right time can suffocate overwintering insects, eggs and mites, reducing the number of pests you’ll have to deal with during the growing season. This also helps to protect beneficial insects in your landscape by reducing the chemical sprays that might be needed during the growing season.

The right timing for your oil spray will depend on what pest you need to control. There are a few pests that should be managed with a dormant oil spray in early spring, but for most pests you’ll want to delay your oil spray until some point between the time buds begin to swell and the time the tips of leaves just start to show. This delayed-dormant oil spray will catch pests as they hatch or emerge from overwintering sites and out onto the tree. The exact timing of a delayed dormant spray will vary depending on the kind of tree and also on the location of the tree.

The oil you use should be a horticultural oil that is specifically formulated for use on plants. It is usually a petroleum or vegetable-based oil. For dormant and delayed-dormant sprays the oil should be diluted to a 1.5-2% solution. If you need to use an oil spray to control mites or aphids during the growing season while leaves are on your trees, you should dilute the oil to 1% or less so that you don’t damage your trees.

For the most up to date information about timing your dormant oil sprays and other pest management spraying and control methods, subscribe to our free email advisories at https://pestadvisories.usu.edu/subscribe.

Just a reminder that we’ve moved. The Utah County office of Utah State University Extension has moved to a new location. You can find us at 1426 E 750 N in Northeast Orem near the mouth of Provo Canyon. You can also send your yard, garden and pest questions and photos to us at gardenhelp@usu.edu.

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