When purchasing houseplants, look at the foliage carefully. Avoid plants with yellow leaves, brown leaf edges or spots which indicate the plant has been poorly cared for. Look for signs of scale, mealybugs or mites that could infest your other plants at home. (NOLA.com|The Times-Picayune archive)
Indoor plants make our homes pleasant and attractive. They may even help remove pollutants from the air, making the indoor environment healthier.
But keeping houseplants healthy can be a challenge. To thrive indoors (or at least survive), we must provide proper light and water. Sometimes, however, we can do everything right and still see our houseplants succumb to pests.
The indoor environment is ideal for pest outbreaks, which usually get started when an infested plant is brought inside. There is no rain to wash off pests, the temperatures are moderate year round, and there are no natural predators inside to help control pest populations once they get started.
Your best defense against major pest outbreaks is close and regular inspections and prompt action should an infestation occur.
Three of the most common houseplant pests are mealybugs, scales and spider mites.
Mealybugs are common and infest virtually all of the plants typically grown indoors. They are small, oval, soft-bodied insects usually covered with a white powdery or cottony waxy secretion. They feed on the plant’s sap, much the way mosquitoes feed on our blood.
Look for cottony masses in the growing points of plants: in the crowns, under the leaves and where the leaves join the stem of the plant.
Since they don’t move around much, many people mistake mealybugs for some sort of fungus infection.
Plants heavily infested will appear unhealthy. The leaves may have a shiny appearance and feel sticky, and the new growth may appear weak and deformed.
Many older leaves will begin to turn yellow and die.
Scale insects are related to mealybugs and also feed on plant sap. Scale insects often are covered with a waxy coating that’s usually white, tan or brown depending on the type of scale.
Once they are large enough to notice, they have settled in one place, and no longer move. This, along with their waxy covering, makes it difficult to notice them; and once you do see the strange bumps or dots on the plant, you would never think they’re insects.
Like mealybugs, scale-infested plants will often have shiny, sticky leaves. Even the floor or table where the plant sits may become sticky. This is a result of the accumulation of honeydew (a sweet, sticky excretion of the scale) on surfaces under the plant.
If the scale population passes the plant’s tolerance, the plant will begin to lose vigor, and the leaves will yellow and die.
Spider mites are extremely tiny (barely visible to the naked eye), and the damage they cause is initially very subtle.
In the early stages, damage to the foliage causes it to appear dull, faded and unhealthy. With close inspection, tiny, light-colored flecks or spots can be spotted in the leaf tissue, a symptom called “stippling.”
As damage increases, new growth may be stunted and deformed, and older leaves may become faded, develop brown edges and begin to drop off.
High populations of red spider mites will form webbing where the leaves join the main stem.
These three pests attack a tremendous variety of plants. Virtually every plant we grow inside is susceptible to one or more of them.
When a pest problem is detected, prompt action is called for.
First, isolate the infested plant. All three of these pests are contagious.
Always wash your hands after working with an infested plant, especially if you are about to handle healthy plants.
Since there are no natural controls indoors, if the pest is to be eradicated, you’re going to have to do the job yourself.
If you would prefer not to use a pesticide, physical control is worth a try, but it requires effort and persistence.
Spraying a plant every day with a strong stream of water directed under the leaves will usually get rid of spider mites. Continue spraying for at least a week. Indoors, this will work well only for plants small enough to move to a sink or shower.
Otherwise, move plants outside to a shady area (weather permitting) for treatment and use a garden hose with a spray nozzle attached.
Mealybugs are sometimes treated with a cotton swab dipped into rubbing alcohol. This is a tedious process and must be repeated numerous times, but it may work on a light infestation.
If you decide to use pesticides, you must choose materials that are labeled appropriate for indoor plants. Do not use sprays that are meant to be used outside or those for controlling indoor house pests such as roaches or ants.
Mealybugs, scale and spider mites all can be controlled by horticultural oil sprays. These insecticides kill pests by suffocation and are relatively low in toxicity. Year Round Spray Oil is an example. If you can’t find an appropriate indoor-safe product, move the plants outside for treatment and then bring them back inside when the spray has dried.
Premixed, ready-to-use indoor plant insecticides containing insecticidal soap, pyrethrin, pyrethrum or other active ingredients are readily available. They are generally excellent for mites and mealybugs but not very effective on adult scale.
Use pesticides cautiously and follow label directions precisely.
Be prepared to make several applications for complete control. Since spraying can be messy, particularly when spraying larger plants, move plants outside to spray them whenever it’s practical.
As you care for your indoor plants this winter, make sure you check them over regularly for pests, and deal with infestations promptly.