Dormant Oil - Timing and Uses

Dormant oils are an effective treatment for pests on plants, particularly during the dormant season. These oils are applied in late fall or early spring, before bud swelling and bud break. This timing is crucial for controlling overwintering insects and insect eggs on fruit trees and woody ornamentals while minimizing risks to plants and beneficial insects.

Using dormant oils can help manage harmful pests and reduce the need for pesticides during the growing season. However, a single treatment may not ensure complete control, so consistent monitoring is essential to prevent further infestations. Dormant oils are effective only when they make direct contact with pests at the correct life stage.

Why Timing Matters 

Applying dormant oil at the right stage in a pest’s life cycle is critical for success. For some pests, the oil works by blocking the spiracles—the air holes they use to breathe. In other cases, it acts as a poison by interacting with fatty acids and disrupting metabolism.

Correct application targets specific pests and their life stages. Avoid indiscriminate spraying, as blanket applications may not be effective and are environmentally irresponsible. As with any pesticide, remember: “A prescription without diagnosis is malpractice.”

Application Guidelines

Avoid using dormant oil in combination with sulfur or sulfur-containing pesticides, as this can cause phytotoxicity, negatively impacting plant health.

Do not apply dormant oil on sensitive plants such as junipers, cedars, Japanese and red maples, smoke trees, and spruce, especially dwarf Alberta spruce.

Apply when temperatures remain above 40°F for at least 24 hours. If applied just before freezing, the oil’s emulsion can break down, causing it to adhere improperly to bark or leaves instead of targeting pests.

Benefits and Considerations

Monitoring trees is vital. Symptoms from pests like autumn mites may only become evident in spring or summer. Fall applications can prevent such damage by suppressing mite adults, immatures, and eggs. The physical mode of action of oils, causing suffocation, requires thorough coverage to be effective.

Various oils are available for garden use, including spray oil and highly refined supreme oil. While older oils were unsuitable for use after dormancy, modern lightweight oils are safer for foliage. These advancements make it easier for gardeners to apply dormant oils with confidence.

Light Pollution - Effects and Solutions

Have you heard about light pollution and its effect on people, animals, and our beloved yards and gardens? While there is no need to panic, raising your awareness about sensible solutions might just help you and your garden to thrive in the future.

The Effect of Light
The health of plants and ecosystems is reliant on and directly affected by light. The natural, daily flow from day to night slowly changes throughout the year based on the Earth’s rotation around the sun. We call these natural periodic fluctuations in daylight and temperatures, “seasons”. Living things have evolved and adapted to the changes of the seasons based on various environmental factors, like the number of hours of daylight they receive. Summer solstice represents the longest day of the year (and the shortest night). After this day, the length of our days shortens, and nights lengthen as we move away from summer and transition into fall and winter. The reverse happens when we move from winter back to summer. These purposeful light changes cue the plants in our gardens to initiate biochemical changes. For example, garden plants finish forming the seeds, fruits or roots as days get shorter heading into autumn.

Excessive Light
Light pollution refers to the excessive and/or misdirected artificial light produced by humans. In addition to interfering with our body clocks, affecting our sleep patterns, and hiding the beauty of the night sky, it also negatively affects our gardens and trees by creating an illusion of longer days and shorter nights. In the case of our urban trees, especially street trees, the leaves and buds that experience prolonged “daylight” perceive an endless summer. Affected leaves keep on growing, while the leaves farther away from the light source can start to senesce and change colors. The dormancy of landscape trees is greatly affected by high-intensity light sources, such as high-pressure sodium lamps.

Artificial light is extremely harmful to insects, as well. The light attracts insects that don’t normally move from their habitat, disrupting normal flight activity. Moths are one victim of this. Because of these disruptions to insect life in the evening and at night, our pollinators are being affected. Due to habitat loss, these pollinators are already under pressure to perform. We need them so that we can have successful home gardens.

Reduction of Light Pollution
Light pollution is fairly easy to reduce. Simply dimming outdoor lighting or directing it only where needed can make a huge difference. Other solutions include changing the color temperature of outdoor lighting. Warm tones such as amber-colored bulbs are the least harmful. Timers and motion sensors can also help, since they aren’t lighting up except when necessary. Using streetlights that point light only where needed are also a solution that many cities across the world are implementing.

It is estimated that as much as 30% of the electricity generated to turn on our outdoor lights is squandered by being misdirected into the sky. Using the appropriate light type, just when it’s needed, can go a long way towards saving energy and allowing our plants and trees to bud, flower and fruit appropriately.
 
While some light is necessary if we are going to drive our cars and spend time outdoors at night, it has not been proven that more lighting is better. More light causes glare off the road for nighttime driving. Using only the light that we need will be better for the pollinators and for our trees and plants.