Common Houseplant Pests – Part 2

By: Jennifer LaMontagne – Assistant Horticulturist – Bloch’s Farm – Green Lake, WI

Last week’s article discussed the common houseplant pest, the mealybug. Unfortunately, there are more pests that cause our houseplants to suffer including spider mites and aphids. How can these infestations be identified, and how can they be stopped or prevented altogether?   

Spider mites are tiny spiders hardly visible to the naked eye. With a hand lens you may notice that the creatures have eight legs rather than six, which is typical of many insects. Like most spiders, they spin small webs. Spider mite webs are visible beneath and between leaves and over flower buds. Small yellow or brown spots (stipples) may also appear on the tops of leaves. A severe infestation will give the plant a dusty look, and the leaves will eventually turn a rusty red color before dropping off.  

Houseplants are susceptible to spider mites because of the favorable warm temperatures, dry conditions, and the lack of natural enemies indoors. For early detection, try placing a piece of white paper under a single leaf or the entire plant, and then tapping it. The small mites (about the size of fine sand) are easy to see on the white background as they crawl around. 

To control spider mites; mist the plant regularly with cold water. Spider mites dislike the humidity and the cold. Adding a little insecticidal soap to the water will also help in the battle against this most persistent pest. Remove the webs and the spider mites by washing the plant in soapy water, paying particular attention to the undersides of all the leaves. To ensure complete  removal of the eggs, repeat the treatment every 3 to 4 days until the plant is clear. Insecticidal spray or neem oil may work also well for treatments. For severe infestations, an insecticide containing pyrethrum as an active ingredient works well.

Another common houseplant pest are aphids, which are found mostly on the undersides of leaves, new shoots, and buds. Aphids range in a variety of colors and live in small groups. Aphids suck out juices from the plants, causing stunted growth, and distortion of buds and leaves. Like the mealybug, they also excrete a sticky ‘honeydew’ which can attract a black sooty mold. 

To control aphids, remove as many as possible by hand with a soft brush. Then take the plant and rinse it upside-down in a weak solution of soapy water. Take care not to water the soil with the soapy solution. If the soapy water does not work, you can use common insecticides. Aphids are becoming resistant to some of the commonly used chemicals, so make sure to read the label front and back to see if it controls aphids. 

Bloch’s Farm will be opening soon. We are busy getting ready for all your spring needs! Call 920-294-6000 or e-mail jlamontagne@blochsfarm.com with any questions. You can also check out our website online at www.blochsfarm.com and follow us on Facebook and Instagram.

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