By Amy Jo Detweiler

Oregon State University Extension Service

Q: Can I use dish soap to control garden pests?

A: We know it works on greasy dishes, but does Dawn really work on cleaning up your garden insects?

You’ve heard it before. A little bit of dish soap, water and a spray bottle and you’re armed and ready for battle with garden pests such as whiteflies or aphids.

But does it really work? In a comparative study of both commercially available insecticidal soap and dish soap, both were effective at reducing pest populations on plants. In fact, one study showed that dish soap was even more effective in reducing pest populations than the commercial insecticidal soap.

However, those plants treated with dish soap also sustained damage.

The components in dish soap remove the waxy cuticle on insects (this is good), but also remove it from the plants (not so good). The problem with some homemade remedies is that they haven’t been extensively tested and may do more harm than good.

In the long run, it is worth spending the few extra dollars to buy the commercially formulated insecticidal soap as it will be safe to apply on plant material and also manage your pest population.

— Amy Jo Detweiler is an associate professor of horticulture at Oregon State University Extension Service