Ask a Master Gardener: How do I get rid of aphids and ants?



Ladybugs feed on aphids and many other garden pests.


Question: Last year I had a horrible problem with ants and aphids in our garden. They got on everything. Can I do anything to keep that from happening again this year?

Answer: Yes. Let's start with the aphids. They seem to simply appear out of nowhere when the weather settles down, and before you know it, plants can be covered. Not only are they unsightly, but they spread disease and suck nutrient from plants.

If you have lots of aphids you are also likely to have lots of ants. The reason for that is that the ants treat aphids as their "cows." Excess sugar and sap are emitted by the aphid, and the ants must consider that close to nirvana, to judge by their close attendance to their "cows." Ants distribute their aphids among several plants, quickly spreading any disease that might be present in the aphids. In the fall, ants carry aphid eggs into their nests to be carried back out in spring and let on plants. This makes control difficult, as you have experienced.

There are many controls available for these soft-bodied plant lice. And it's a good thing, as there are many types of aphids, often named for their favorite food choice. Perhaps the easiest way to control aphids is to direct a strong stream of water to wash them off your plants. They then seem unable to get back on. Or you can gently rub leaves, crushing them. A slightly stronger control is an insecticidal soap spray. Some people swear that growing nasturtiums as a "trap crop" works. Wait until the nasturtiums are covered with aphids, which doesn't take long, then pull them up and destroy the plants, along with their unwelcome pests.

The best-known predator is the ladybug, but many more insects love to chow down on aphids, including spiders and lacewings.

Since ants are often the major source of aphid problems, controlling them will yield benefits. Sprinkle Diatomaceous earth, a natural substance with a coarse surface, around your plants most plagued by ants and aphids. No soft-bodied insect wants to climb over it for fear of getting cut up.

Good garden hygiene and cleanup of plants debris will help cut down on both ants and aphids.

One interesting solution to aphid infestations was suggested recently, and I will definitely try it out. Rhubarb leaves contain oxalic acid, which kills aphids. It is poisonous in high concentrations. The stems of rhubarb contain negligible oxalic acid, but its leaves should never be eaten. Mix up a simple rhubarb spray by cutting up 1 pound of leaves and boiling them for 30 minutes or so. Strain and bottle the liquid, and to help it stick to the leaves, add a bit of liquid soap when the mixture has cooled.

If you try this remedy, report back to me with how it worked for you. Rhubarb grows well in this climate. So do aphids!

Q: I've been told that a few chemicals can be used as "organic pesticides." They are carbaryl, diazinon, and malathion. Is this information true?

A: Absolutely not. Not one of these chemicals is an organic pesticide. Several reasons not to use them include their impact on our water system, as well as residual amounts in the food that is grown using them.

There are many ways to deal with garden pests. The first thing to do is identify what pest you have. Then consult any good gardening book, a nursery person, or the Whatcom Extension Office, 360-676-6736, for help determining what kind of pest you have and how to deal with it. Insects far outnumber humans and will be around much longer than we will. Knowing this helps to learn that 100 percent eradication of pests is not only impossible, it probably isn't good. Every insect is part of the bigger scheme!


Master Gardener Kathleen Bander is a resident of Bellingham and life-long gardener. For more information on Whatcom County Master Gardeners, go to

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