Winter can be hard on indoor plants. “Low light, shorter days and dry air create a stressful environment for our houseplants while at the same time helping insects thrive,” explained gardening expert Melinda Myers. Myers said not to despair if insects have moved in and plants are struggling with yellow or speckled leaves. She shared these eco-friendly strategies to diagnose the problem and manage insects, so houseplants stay healthy and look their best.
Start by making sure houseplants are receiving the proper amount of light and water. A healthy plant is better able to resist and recover from insect infestations. Check the plant tag, internet or plant book for the recommended growing conditions. Make any needed adjustments to the plants’ care.
Take a close look at the upper and lower leaf surfaces and stems of the plants for clues to the cause of the problem. Here are some of the more common indoor plant pests and organic options, safe for children and pets, for managing them.
Fungus gnats are those small fruit fly-like insects that flit around the house. They feed on plant roots and organic matter in the soil. They usually don’t harm the plants, but certainly are annoying.
Just sprinkle an organic insecticide, like Summit Mosquito Bits, that contains the active ingredient Bacillus thuringiensis israelensis on the soil surface. This naturally occurring bacterium only kills the larvae of fungus gnats, black flies and mosquitoes.
Aphids are common pests of indoor and outdoor plants. These small teardrop shaped insects suck plant juices, causing the leaves to yellow, brown, wilt or become distorted. They secrete a clear sticky substance known as honeydew.
Mites cause similar damage, but are too small to see without a hand lens. If mites are suspected, shake a leaf over a white piece of paper and watch for specks, the mites, moving across the paper. Don’t wait until webbing is visible to control these pests. At that point there are thousands of mites making it difficult to control.
Both these types of pests can be managed in the same way. Start by placing plants in the sink or tub and knock the insects off the plant with a strong blast of water. Follow with several applications of insecticidal soap to kill the adults. Repeat as needed. Or suffocate all stages of the insects with a lightweight horticulture oil like Summit Year-Round Spray Oil.
Bumps on the stems and leaves of plants that can easily be scraped off with a thumbnail are scales. Their shells protect the adults and eggs from predators, weather and most insecticides. A similar pest, mealybug, has white waxy strands on its body for protection. Mealybugs can be found on stems, leaves and area where leaves and stems meet.
Both types of insects suck the plant juices, causing leaves to yellow and plants to decline. And just like aphids and mites, they secrete honeydew. Both are difficult to control and require persistence.
For mealybugs, remove the hard scale covering with an old toothbrush. Use a cotton swap dipped in alcohol to dissolve its waxy covering and kill the insect. Then spray with insecticidal soap to kill the immature insects. This takes time and persistence to control these pests.
Or apply a lightweight horticulture oil, like that used for mites and aphids, to suffocate both the adult and immature stages of these pests. Continue to watch for outbreaks and treat as needed.
No matter what products, natural or synthetic, make sure they are labeled for the plant and pest that are being treated. And always read and follow label directions carefully.
Investing time in managing pests as soon as they appear means healthy and more attractive plants to brighten the indoors now and for years to come.
Melinda Myers has written more than 20 gardening books, including Small Space Gardening. She hosts The Great Courses “How to Grow Anything” DVD series and the nationally syndicated Melinda’s Garden Moment TV & radio segments. Myers is a columnist and contributing editor for Birds & Blooms magazine and was commissioned by Summit for her expertise to write this article. Myers’s web site is http://www.melindamyers.com.