Houseplant pests - Landscape Ontario

June 4, 2013

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 plants' 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 their temperature and light combinations are mixed up. The plant is, again, stressed. When it's 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. It is warm in winter, so plants grow quickly but there isn't strong light; therefore, the growth is spindly. Plants prefer a cooler night temperature than day temperature 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, but 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 10 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 plants' immunity to fungi and diseases as well.

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. Wash off with stream of water, Safers Soap or ladybugs are possible cures.

Fungus gnats
These insects are black 1/16-in. 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 nicotine (let a few cigarette buts sit overnight in a half glass of water and use that scary water as a drench) will help reduce fungus gnats. Also reduce general watering, let the soil dry to about 2 cm deep before you water the plant.
*May be toxic to some plants.

Mealy bug
Mealy bugs look like fluffy pieces of cotton 1/8-in. to I /4-in. 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 of growth, yellowing, leaf distortion and a sticky sap (that is undigestable by insect) left on the furniture, leaves or floor below the insect. It is controlled by using rubbing alcohol, undiluted, as a good home remedy.

Scale
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, slow growth or no growth 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. Rubbing alcohol with a cloth is the organic control.

Spider mites
Spider mites may be green, red or brown and you can see them by using a magnifying glass or by tapping a 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 Safer's Soap with a Pyrethrum in it. Be sure to cover every square inch of the plant, particularly the underside of leaves.

Whitefly
Whiteflies are approximately 1/12-in. long. Whiteflies may begin fluttering about if a plant is disturbed. Leaves will become mottled and yellow. Whiteflies stick their sucking mouth parts into the plant tissue, they then lose their legs and become like a scale. To control, use Safer's Soap or wash off with stream of water.

Organic controls will also work, search online for recommendations, but Safer's Soap, drenches with tea or nicotine are examples of organic cures.

As you can see, there are many types of insects that can affect your houseplants. Most are not immediately noticeable to the untrained eye, so there may be a lot of damage before you detect it. Try to be aware of any abnormalities in your plants, and be a good researcher before buying your plant material.

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