Spray Oils Effective in Aphid Control

Q. My 30 foot tall live oak tree is covered with aphids. Should you spray now or will the aphids die if the weather gets cold?

Aphids on southern Live Oak

A. Aphids overwinter at the base of trees and weeds nearby. Their populations are much smaller, but they are there. Eliminate weeds and apply “dormant oil” to the tree twice; once in December and again in January before new growth begins.

            Dormant oil is a holdover name from decades ago when forms of this oil were safe to apply only during the winter. You might find this product now with names like horticultural oil, superior oil, supreme oil and others.

Oil for spraying in a pint container. This company has chosen to call it a horticultural oil.

            These newer oils are different. These are not vegetable oil or neem oil used as insecticides but a different type of oil that “smothers” overwintering bugs. I have used these newer oils in the fall, spring and even early summer months as long as the plants are not flowering.

This oil for commercial use is in 2 1/2 gallon container. This company chose to call it Ultra Pure Oil

            Ants and aphids rely on each other. Controlling ants helps control the spread of aphids and keeps them in check. Controlling ants when aphids are problems is an important component when controlling aphids. I like to use ant bait products like Amdro applied exactly as the label says.

One of the ant baits supplied by Amdro

            Don’t worry about small numbers of aphids on trees if you eliminated weeds and controlled their ant buddies. Leave them alone unless there is some problem you can’t live with. If the ant problem is intolerable, apply soap sprays, neem oil or a systemic insecticide if it’s a bad problem. But don’t go in that direction unless you must.