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Essential Oil: What You Need to Know About Horticultural Oil

For property owners with environmental concerns, the use of pesticides often proves an issue, which is why horticultural oil provides a great and effective solution without being hazardous. Most types of horticultural oil use mineral oil, which is a refined petroleum product. Vegetable oils such as cottonseed oil and soybean oil are also effective yet environmentally friendly pesticides. Typically, in the formulation of horticultural oil, some type of emulsifying agent combines with the mineral or vegetable oil. This is necessary so that it can effectively mix with water for use as a spray on plants and trees.

Horticultural Oil History

Horticultural oils were originally popularized as a method of pest control on fruit trees, which needed special care because of the edible nature of their yield. Even though they are highly vulnerable to pesky insects, these fruit trees couldn’t be treated with traditional chemically based pesticides, as it would make eating their fruits dangerous. Also, the pesticides threatened beneficial insects rather than targeting only the dangerous pests, which would disrupt the pollination process and endanger the crop. Because of this, a natural, oil-based form of insecticide came into development for use during the trees’ season of dormancy.

These early versions of horticultural oil –called “dormant oil” – were too heavy for use on actively growing plants without risking damage to the foliage. Over the years, refining processes led to the creation of lighter-weight oils safe for use during periods of active growth. Still, it was necessary that these “summer” or “all-season” oils be used with caution, as plants treated with oils will burn in the heat of the sun.

Horticultural Oil & Insecticides

Despite their toxic-free formulation, many plants don’t tolerate the use of oil. To remedy this issue, new versions combine horticultural oil with additional insecticides for more effective use with less risk of damage to the plants. Now that processes have refined things even further, all horticultural oils are safer for use during the growing season as well as dormant season, broadening their use. Even so, it is important to note that rates of application vary by the season.

How Does it Work?

How do horticultural oils work? The concept is simple enough. Essentially, they suffocate insects, as the oil blocks their breathing ability by blocking their spiracles. They also disrupt the ability of some insects to feed and the metabolism of insect eggs, starving them to death. The most common insects controlled by horticultural oil include adelgids, aphids, caterpillar eggs, leafhoppers, mealybug, mites, scale, spider mites, thrips and whiteflies. It is also effective for use on plants with powdery mildew.

Is It Safe?

Safe as it is, horticultural oil is still a pesticide and should always be used according to the label’s instructions. All bugs – both beneficial insects as well as pests – are vulnerable to the effects of horticultural oil, so it’s important that it is only used as needed. To use, spray the oil directly on the pests, not on the plants. Excess oil dissolves quickly, leaving no toxic residue behind. Unlike many insecticides, it is safe for use around humans and animals.

Add Oil for Best Results

For times recommending the use of so-called “dormant oil,” apply the horticultural oil just before the buds of leaves or flowers show signs of blooming or opening. Applying it before insects are active on the plant and breathing, however, makes it ineffective. Summer applications of horticultural oil are less complicated, as this is when young, soft and slow-moving insects are most active rather than mature insects, which are less affected by the oil. Watch for the first appearances of insects before applying the oil.

Oil Don’ts

Do not use horticultural oil during times of extreme heat, as heat-stressed plants or those experiencing drought conditions are vulnerable to damage caused by the combination of oil and sun, which burns them. Freezing temperatures are also an ineffective time for horticultural oil use. The emulsion does not hold together, causing uneven coverage. Wet plants and periods of high humidity cause the rate of evaporation to decrease greatly and risks burning the foliage. During fall, application increases the risk of winter damage and dieback.

At Executive Landscaping, Inc., we have years of experience in safely controlling the presence of pests on our clients’ plants and trees with horticultural oil. No matter the issue, we have a solution that maintains the beauty of your property and keeps the environment safe.

Call Executive Landscaping, Inc. to learn more about the benefits of horticultural oil and the many outdoor services we offer today!