Horticultural Oil: What is it? And How Does It Work?

Horticultural oil also known as white oil is a pesticide and should always be used according to instructions.

Using horticultural oil spray on common houseplant pests has become accepted today. They were first used in treating fruit trees in the 1880s. This is because fruit trees were susceptible to pest attacks. The use of regular pesticides on fruit trees could have negative effects on the fruits. 

Horticulture oil became a recommended choice as they were both effective and natural.

So, what are horticultural oils?

What It Is Made Of

These oil-based pesticides were created with the main purpose of killing plant pests. They were made with mineral or petroleum products that were harmless to plants. They also contain plant-based products like neem oil, soybean oil, and others. 

The first versions of horticultural oils were called Dormant oils. They were too heavy for growing trees and could often harm the plant’s foliage. So they had to be used in their dormant stage. This is where they got the name from. 

As time progressed, a more refined version of dormant oils was created. They were called Summer oils. These oil-based insecticides could be used on plants during all seasons but they had a flaw.

During the hot season, summer mineral oil for plants could cause burn damage to the plant’s foliage. To further improve the insecticidal oil, they were refined and made into Superior oil. This mineral oil insecticide contained no sulfur making it a safer horticultural oil. 

Now, all versions of horticultural oils being produced are superior oils. But they are called “horticultural oils” to help keep things simple. 

Using Horticultural Oils, How They Work

The idea behind horticultural oil application as insecticides is quite simple. They restrict the airflow of the insect and kill them by suffocation. 

In addition to that, Hort oil also reduces the ability of common houseplant pests to feed. This then leads to the death of each insect.  They also affect insect eggs by disrupting their metabolism. This can hinder them from hatching…

For horticulture oils to work, there has to be direct contact with the insect. This means ensuring that the entire infestation is covered by the pesticide. 

What Pests Are They Used For?

Horticultural oils work for a wide range of pests and insects, here are a few; 

• Aphids
• Mealybugs
• Scales 
• Mites
• Spider mites
• Thrips 
• Leafhoppers
• Whiteflies
• Powdering mildew

Why Use Horticultural Oils?

There are a few benefits of using organic horticultural oils on insect infestations. Because they are made using organic products, they are a bit safe for wildlife and humans.  

They are also safer for beneficial insects than regular chemical pesticides. This is because the oils are quick to degrade or evaporate, leaving no residue that could be toxic. There is also a low chance of insects developing a tolerance to the pesticide. 

This is because the way they work isn’t chemical but mechanical (by suffocating the insects). For the best possible result, you should use it as directed by the packaging or label. 

Are There Any Disadvantages To Horticultural?

The short answer is yes.  There are a few disadvantages to using horticultural oils. Not all plants react well to horticultural oils. Some plants like smoke trees, cedar, and maple are too sensitive to oil insecticides. They are prone to get burned by constant use.

Also, horticultural oils can be a little toxic to humans. They could cause mild irritation to the eyes and skin of people. This is why it is recommended that you wear protective gear during use. 

They can also be a little toxic to a few wildlife creatures like bees and even fish. So avoid spraying next to them. 

When To Use Horticultural Oils 

The best time to use horticultural oils would be when its targeted pests are most active. Monitor the affected plant and spray when you notice signs of the plant’s leaves or flower opening. 

This is easier during the summer season as the insects should be most active then. They are best used on slow-moving insects. 

Do not use hot oils during very high or low temperatures. Doing this can cause foliage damage to the plant. 

Also, avoid using pest oil during the rainy season (fall season). The oil could cause further water damage to the plant and cause dieback. 

Frequently Asked Question