Horticultural Oil

Marijuana Horticulture

by Jorge Cervantes

Ingredients – Often underrated and overlooked as an insecticide and miticide, horticultural oil is very popular in greenhouses and is regaining popularity among indoor growers. Similar to medicinal mineral oil, horticultural oils are made from animal (fish) oils, plant seed oils, and petroleum oils refined by removing most of the portion that is toxic to plants. Lighter weight oil (viscosity 60-70) is less phytotoxic. Vegetable oil is also horticultural oil.

Controls – Virtually invisible, horticultural oil kills slow moving and immobile sucking insects, spider mites and their eggs by smothering, as well as generally impairing their life cycle.

Caution – Do not use lubricating oil such as 3 in 1 or motor oil.

Mixing – Mix 3/4 teaspoon (0.75 cl) of oil spray – no more than a one percent solution – per quart (0.9 L) of water. More than a few drops could burn tender, growing shoots.

Application – Spray foliage entirely, including under the surface of the leaves. Apply oil sprays up until two weeks before harvest. Repeat application as needed. Usually three applications, one every five to ten days, will put insects and mites in check. Lightweight oil residue evaporates int the air in a short time.

Persistence – Disappears in one to three days, under normal growing conditions.

Forms – Liquid.

Toxicity – Safe, nonpoisonous, and nonpolluting insecticide. Can become phytotoxic if too heavy (viscosity)), if applied too heavily, or when temperatures are below 70F, or very humid; this slows evaporation, increasing phytotoxicity.

Safety – Wear a mask and gloves.