Rosanne Loparco
| Utica Observer Dispatch
Be proactive this spring and do something to control insects or diseases on your fruit trees before problems arise during the growing season.
Horticultural oils as a dormant spray are an important organic option for pest control.
Horticultural oils are highly refined petroleum (or plant based) products that are filtered and distilled to remove compounds that harm plants. Products are mixed with water and sprayed on fruit trees using a hose-end sprayer or pump sprayer.
The term “dormant oil” refers to when the oil is applied rather than what it’s made of. Sprays can control overwintering insect pests such as aphids, caterpillar eggs, and more. Because dormant oil sprays are effective on aphid control, the sprays can also mitigate viruses carried by aphids. Dormant oil sprays also minimize diseases such as powdery mildew, downy mildew, rust, and leaf spots.
Don’t apply a dormant oil spray too early (i.e., a warm day in February or March), before insects or fungi are susceptible to the oil’s suffocating effects. Apply in late March or April, before fruit tree leaves or flowers show signs of breaking dormancy: before “bud break”.
Watch the weather. Apply when temperatures are above 40 degrees F. for 48 hours to prevent tree injury. There is a second option for timing the application since an early spray can speed up bud development in early blooming fruit varieties, making the buds more susceptible to late frost damage.
To prevent this, apply dormant oil when buds are just open at the tip showing 1/16 -inch to 1/2-inch of green tissue. This is called a “delayed dormant” application.
Read product labels completely and follow instructions. If you are growing tree fruits, let Cornell Extension help you; visit https://tioga.cce.cornell.edu/gardening/tree-fruit-growing for all the information you need. For more information on horticultural oils, visit Colorado State Extension for their fact sheet, https://extension.colostate.edu/resource/insect-control-horticultural-oils/.
Learn more and attend our CCE Oneida County Master Gardener Fruit Tree and Berry Workshop on Saturday, March 28, 2026, from 9 am to 1 pm, at the Rome Art and Community Center (RACC), 308 West Bloomfield Street, Rome, NY. The cost is $30 per person and pre-registration is required. Our featured presenters will be Ms Anna Wallis, Fruit IPM Coordinator from Cornell’s IPM College of Agriculture and Life Sciences, and Natika Walters, CCE Oneida County Agriculture Educator.
We will also have presentations on growing raspberries, brambles, and figs as well as tree fruits. To register, visit our website at https://cceoneida.com/events/2026/03/28/fruit-tree-berry-workshop or call Holly Wise, 315-736-3394, Extension 125, or email hlw2@cornell.edu. Space is limited; so, register now. I hope to see you there!
Cornell Cooperative Extension Oneida County answers home and garden questions which can be emailed to homeandgarden@cornell.edu or call 315-736-3394, press 1 and ext. 333. Leave your question, name, and phone number. Questions are answered on weekdays, 8am to 4pm. Also, visit our website at http://cceoneida.com/ or phone 315-736-3394, press 1 and then ext.100
Comments are closed.