Now is a good time to clean those pests off your houseplants


Most people don’t like to spray pesticides inside their homes. I don’t blame them. I do like houseplants but so don’t certain insects and other critters. Sometimes we can use soil applied granular chemicals, but some people with pets are even hesitant to do that.
One method I sometimes use is soaping foliage in the shower with a mild dishwashing detergent. I leave the lather on the plants for a while. Then I rinse it off and send the nasty critters down the drain. This technique works great for a small number of plants. However, some people feel funny about using their shower as a plant washing station.
With recent milder weather we can treat our plants outside, either with commercial pesticides or the soap treatment. Either way, doing it outside eliminates some of the odor and mess. If we get several mild nights we can even let them stay outside for a while. If you do this make sure to keep plants out of direct sunlight. You’d be surprised how different light intensities are, even in a well-lighted south-facing room.
I have found the biggest culprits of houseplants to be mealybugs, spider mites, scale, and fungus gnats. With the exception of fungus gnats they are all difficult to control. Scale, mealy bugs and spider mites often require multiple treatments.
Fungus gnats are pretty easy. The first step usually involves reducing soil moisture levels. This is most important as these insects feed on fungi growing in the soil. Eliminating that alone is often enough to control them, but most insecticides are effective as is the soap treatment.
The other three require systemic insecticides, since those three arthropods have sucking mouthparts. This means they feed from inside the plant. Systemic means the chemicals are absorbed into the plant and aren’t simply resting on the leaf surface.
Acephate and Imidacloprid are two chemicals that are effective and labeled for most houseplants. They are also readily available and don’t require a pesticide applicators license. The most common application method is to spray the foliage completely. Usually two or three applications at ten to fourteen day intervals are recommended.
Another option is to use soil applied granules and add additional soil to cover the residue. These usually can be effective for several months. Sometimes I use an initial soap cleaning followed by systemic granules. This is also effective for aphids, which often attack tropical hibiscus, especially the flowers.
It is important not to exceed labeled rates. They are established through thorough research. Never assume if a little is good, then more is better. Many chemicals are toxic to plants at higher levels and they certainly can be unsafe to people applying or living around them.
I try to minimize my use of pesticides, but sometimes they are the best option to control pests on your houseplants. Always keep records of what, when and how much you applied. Also, it’s helpful to rotate chemicals and not use the same pesticide all the time.

Ted Manzer teaches agriculture at Northeastern High School.

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About tedmanzer

I grew up in Old Town Maine and got a B.S. at the University of Maine in Plant Sciences/ minor in Botany. From there I moved to West Virginia and earned a M.S. in Agronomy at WVU. I also met my wife there. She grew up in rural WV as the daughter of tenant farmers who raised cattle and hogs. Their lifestyle at times was one of subsistence and I learned a lot from them. I've always been a foraging buff, but combining my formal botanical knowledge with their practical 'Foxfire-type' background opened up my eyes a little more. I now teach agriculture to high school students at Northeastern High School in Elizabeth City, NC. My wife teaches with me and we make a great team. I also write a weekly nature/foraging column for the local paper (dailyadvance.com) and frequently publish articles in several other newspapers in northeastern North Carolina. I also have written several Christian nature/adventure novels that I plan to publish eventually. One is a five book family saga I call the 'Forgotten Virtues' series. In the first book, Never Alone, a young boy comes of age after his father dies in a plane crash, and he has to make it alone. Never Alone is now available in paperback, Kindle and Nook. The second book, Strange Courage, takes Carl from his High School graduation to his recovery from a nasty divorce. The third book, Second Chances, takes Carl from his ex-wife's death and the custody of his son to his heroic death at age 59. The fourth book, Promises Kept, depicts how his grandchildren react and adjust to his death. In the final book, Grandfather's Way, his youngest and most timid granddaughter emerges from the shadow of her overachieving family and accomplishes more in four months than most do in a lifetime. I use many foraging references with a lot of the plants I profile in these articles in those books.
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One Response to Now is a good time to clean those pests off your houseplants

  1. These are excellent ideas! I was noticing the house pests starting to pick up not that the weather’s warmer…
    I love the natural ways to fix this-I even got a pet tree frog to eat the flies and so far it’s working!

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