Houseplant Pests

Houseplants are like people. When they become weak or under stress, they get sick and require a doctor’s care. Preventative measures will reduce the amount of insects your plant will acquire.

Preventative Maintenance

Plants should be chosen to suit the conditions in your home, thereby decreasing stress right from your initial purchase. Through proper care, plants will remain strong and able to fight off some, if not all, infestations and infections. By over watering or under watering, plants will be easy prey for hungry insects. Temperature is also a factor in your plant’s health and susceptibility. In the winter months, the air has a tendency to be dry and these are perfect conditions for insects to thrive. To reduce hot, dry conditions around your plants, place a tray filled with pebbles and water under your plants. The water should not touch the bottom of the pots. Evaporation from these trays will create a cooler, humid atmosphere.

Plants may also be confused by air conditioning, as they have their temperature and light combinations mixed up. The plant is, again, stressed. When its cool, a plant is programmed to be dormant, but the light is high in summer so the plant wants to grow but not to its optimum level. In winter its warm, so plants grow quickly but there isn’t strong light; therefore, the growth is spindly. Plants prefer a cooler night temperature than day temperature in order to grow most vigorously.

Insects get into your home in a variety of ways. They may have come in on a pet or yourself brushing up against an infected plant elsewhere. New plants introduced to the area may have brought them in. Your plants may even have already had the insects and the symptoms were not noticed until new plants showed signs. Plants will also pick up any insects if left outdoors for the summer. Be sure to spray two or three times at seven to ten day intervals before bringing them back indoors, or be sure to give them a good check up. High light plants tend to be more susceptible as their conditions for optimal growth mirror that of the insects. Unless an unhealthy plant is nearby or it is the winter season, low light plants are less likely to get insects. All the conditions above will influence your plant’s immunity to fungi and diseases as well.

Fungus Gnats

These insects are black 1/16î flies. They won’t harm plants but do irritate people. They may however, be an indication of problems to come due to overwatering.  They are soil borne organisms that hatch and then fly around looking for somewhere to lay their eggs. A soil drench of *Diazinon according to manufacturers instructions will eliminate the insect. *May be toxic to some plants.

Mealy Bug

Mealy bugs look like fluffy pieces of cotton 1/8î to I /4î long. They can be found on the undersides of leaves but more often congregate around the base of the leaves or on stems. Some symptoms are stunting or growth yellowing, leaf distortion and a sticky sap (that is indigestible by insect) left on the furniture, leaves or floor below the insect. It is controlled by using Malathion or rubbing alcohol, undiluted, as a good home remedy.


This insect is as it sounds, a hard or soft brown scale on the woody stems or sometimes on the undersides of leaves. Symptoms are dropping of green leaves or slow growth or none at all. All other symptoms are similar to mealy bug. Young crawler stage of scale is more easily eliminated because there is no waxy shell yet. Use Diazinon, Malathion or Solgard, but try to spray plants outdoors. Rubbing alcohol will also help.

Spider Mites

Spider mites may be green, red or brown and you can see them by using a magnifying glass or by tapping o leaf onto a piece of paper. The leaves may become deformed, speckled, yellow, dehydrated, then turn brown and fall off shortly after. Spraying water onto the plant will reveal the webs they have spun. There may be clusters of tiny white eggs on the undersides of the leaves. If you only see eggs, it may be a good opportunity to begin spraying early in their cycle. Control may be accomplished by using a miticide Diazinon, Malathion or Safer’s Soap with a Pyrethrum in it. Be sure to cover every square inch of the plant, particularly the underside of leaves.


Aphids have fat fleshy bodies that are either green or yellow. They may cause severe distortion or stunting and are good plant disease vectors. They also drop the sticky sap called honeydew onto the leaves. Malathion is effective in controlling aphids.


Whitefly are approximately 1/12î long. If a plant is disturbed, many will begin flutteringabout. Leaves will become mottled and yellow. Whiteflies stick their sucking mouth partsinto the plant tissue then they lose their legs and become like scale. The former stagerequires contact insecticide. The latter requires systemic. Both chemicals should be sprayedat the same time because both stages will be present at any time. Use Ambush.

As you can see, there are many types of insects that can affect your houseplants.

Most are not noticeable to the untrained eye immediately, so there may be a lot of damage before you treat it. Try to be aware if any abnormalities in your plants, and be a good researcher before buying your plant material.


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“Approved Member” status, we assure our customers receive a high level of service, a good range of quality plants and associated products, together with professional advice and information.

December 29, 2023 — Garrys Garden Gallery