Horticultural Oils

Horticultural oils are an option for insect control in the garden, but not all oils are created equal. Retired UT Extension Agent Mike Dennison talked about about the nuances of horticultural oils, their effectiveness, and demonstrated proper application techniques.

Types of Oils:

• Mike highlighted the distinction between superior oils and highly refined horticultural oils. While superior oils may sound impressive, they often fall short in efficacy compared to their highly refined counterparts. Horticultural oils, such as neem oil, boast a purity of up to 98%, making them less likely to harm new foliage or sensitive plants.

Mode of Action:

• Horticultural oils primarily operate by suffocating insects and their eggs, blocking their spiracles or breathing tubes. Additionally, they can disrupt cell membranes, leading to desiccation and eventual death. However, achieving complete control requires thorough coverage, as these oils leave no residual effect.

Application Tips:

• Proper application is essential for maximizing the effectiveness of horticultural oils. Mike emphasized the importance of complete coverage, cautioning against spraying in windy conditions or when temperatures are below 40 or above 90 degrees Fahrenheit.
• When mixing oils with water, thorough agitation is crucial to ensure an even distribution. It's essential to follow label instructions and adjust application rates based on plant sensitivity and seasonal considerations. The label will give the information you need to know.

Safety Considerations:

• Unlike traditional pesticides, horticultural oils pose minimal risk to humans and mammals. Mike demonstrated the mixing process without wearing gloves, highlighting the oils' safety profile. However, you still need to exercise caution and avoid inhaling spray mist during application.

Targeted Treatment:

• While horticultural oils can effectively control pests and diseases, they require direct contact for action. This means that beneficial insects may also be affected, although their populations can rebound in the absence of residual toxicity.

Plant Compatibility:

• Not all plants are suitable for horticultural oil treatments. Certain species, including red maples, Japanese maples, walnuts, and hickories, are susceptible to damage and should be avoided. Evergreens and other sensitive plants require careful consideration, with lighter application rates recommended during the growing season. Once again the label on the oil will tell you what to do.

Horticultural oils represent a valuable tool in plant care, offering effective pest and disease management with minimal environmental impact. By understanding their characteristics and following proper application techniques, gardeners can control insects and their eggs in their garden.

Related Video:
Spraying Dormant Oil on Crape Myrtle
Dormant Oils

Related Resources:
General Comments about the Use of Horticultural Oil
Insect Control: Horticultural Oils