Common Pests
Aphids
Generally, aphids are small, soft-bodied squalid insects that grow at a distance of 14 to 18-inch from the ground. Their color varies but can be green, pink, brown, black, or yellow. Some aphids look like they have a powdery, woolly coat due to a waxy coat, and adults have or don’t have wings.
These tiny insects feed on budding new growth or the base of leaves. There are also some that feed on roots. As a result, the leaves become yellowed and misshapen. In addition, new buds may appear to be deformed because the growth is stunted by the aphids. As the aphids feeds, it produces honeydew, which is sticky and makes leaves appear shiny. Mold fungi may grow on honeydew, giving the honeydew an unsightly color to its surface.
Control: If the infestation is mild, spraying water on the insects or wiping them with a cotton swab dipped in rubbing alcohol may be practical. Insecticide soap spray can be used as well. To control aphids around houseplants that are taken outdoors, spray plants with insecticidal soap, neem oil extract, acetamiprid, imidacloprid, cyfluthrin or permethrin.
Mealybugs
Insects known as Mealybugs are pale, small, insects related to scales. They are about 18,000 to 15,000 years old, and move very sluggishly. Some adults possess waxy filaments that extend beyond their bodies, so they appear cottony. Females also have waxy, white material covering their eggs and bodies.
Nymphs hatch from eggs. Once they begin to feed, they start to acquire a waxy coating. Nymphs resemble adults only much smaller. The waxy coating helps mealybugs repel pesticides, making them difficult to control. One species feeds on the roots, causing stunted growth and plant death, or in most cases death of plant. Like aphids, mealybugs excrete honeydew that provides favorable conditions for growth of sooty mold fungi.
An easy method to control light infestations is to remove each mealybugs manually or wipe them with a cotton swab dipped in rubbing alcohol. An insecticidal soap may also be used. If the infection is severe, it may be necessary to discard the plant. Confront mealybugs while spraying with neem oil extract, pyrethrins, imidacloprid, cyfluthrin or permethrin. Imidacloprid plant spikes put into the soil will also control mealybugs.
Spider Mites
Since mites are exceptionally small, plant damage is typically the first sign of their presence. A silky web is frequently seen with heavier infestations. They are not insects at all but are closely related to spiders.
Both spider mite adults and their immature forms draw sap from plants and leave light-colored spots on leaves. Plants become overly faded as a consequence. When spider mites are not checked, leaves become bronzed or yellowed, and the plant dies. Spider mites are normally more of a problem in plants that are kept inside all year long.
Using an insecticidal soap, spray the plant undersides with water to dislodge the mites. Use water on leaves to break up the webs. Houseplants exposed to the outdoors may be sprayed with insecticides such as sulfur, neem oil, or insecticidal soap. Most of the time, a weekly spray is necessary to prevent mites on houseplants outside.
During summer, placed plants outdoors are commonly less prone to spider mites. Be sure to place all houseplants in a shady environment at first, as even plants that thrive in more sun can be damaged until they are accustomed to a higher light level.
Fungus Gnats
They have an unpleasant odor, and are tiny, about 1/8-inch long. They can often be seen hopping in the soil or flying close to the soil surface near a houseplant. They are weak fliers, and are attracted to light.
Although insects do not normally feed on houseplants, their presence on nearby windows in severe infestations can be a nuisance.
These fungus gnat larvae are whitish with a black head and can be up to 14-inches long. They feed on decaying material in the soil or fungi growing within it. The larvae of some species will also feed on the roots of plants. This feeding is especially damaging to very young plants. With mature plants, you will see that the plant takes on a wilted appearance that is similar to the appearance of a plant that has lost its leaves.
Plants grown in potting soil with high organic content, such as peat moss, are prone to fungus gnats, especially when they are overwatered.
Drying soil between watering is the most effective method of controlling larvae on plants that tolerate it (i.e. most houseplants during the winter). Houseplants should not stand in water in the saucer beneath their containers, and saucers placed outside should be inverted so that rainwater does not collect in the saucers. Some biological control agents can be applied to the soil and watered into the soil to control pests such as Bacillus thuringiensis subsp. israelensis.
Root Ball Pests
Taken outdoors during a hot summer, houseplants may encounter pillbug, millipede, and slug infestations. These pests may cause damage to the root systems. Ants may also make nests inside potted plants while outside. They are commonly found along the outdoor root ball in small cavities in the potting mix.
Check the plant container for pill bugs, millipedes and slugs with a simple scrape. Ant colonies in the pot may be eliminated with soil drenches containing cyfluthrin or permethrin. Pour insecticide solution throughout the soil in the container. Let the solution drain thoroughly before bringing pots indoors. Mix insecticide at the same rate as for spraying.
Scales
Houseplants are prone to scale infections from several species of scale insects. There are two types of scale insects: armored scales and soft scales. An armored scale secretes a waxy covering that is separate from its body. A soft scale’s waxy covering can be scraped off to locate the insect living beneath it. On the other hand, a hard scale’s waxy covering is essential to its body.
Insects known as scales are small, inanimate insects with no legs. They appear flat and a little discolored. In contrast, some others appear like waxy, colored masses. Scales range in size from 1/ to 1 inch in diameter. Their habitat consists of stems and undersides of leaves, though they may occasionally appear on the upper surfaces. They feed on plant sap.
The soft scale insects are mobile when immature and feed by sucking sap. They are similar to mealybugs in that they produce honeydew (resulting in black sooty mold on foliage and stems). The armored scale insects do not produce honeydew.
Adult scales can be removed via sanding or scraping before they develop into adult insects due to the waxy covering on their bodies. However, for perennials placed outdoors, sprays with products that contain natural oils can help control scale insects. Their crawlers can be treated with insecticides such as insecticidal soap, canola oil, neem oil extracts, acetamiprids, imidacloprid, cyclfluthrin, and permethrin.
Whiteflies
In contrast to true flies, whiteflies are more closely related to scales, mealybugs, and aphids. They are very small about 1/ -inch in length. They have a powdery white appearance, just like tiny moths. During the immature stage, the wings are scale-like and are not mobile. When at rest, they are held at an angle resembling a roof over the body.
They feed by sucking sap from plants. The damage that they cause is similar to that caused by aphids. The affected plant can become stunted. Whiteflies cause leaves to decay and turn yellow and die. Like aphids, whiteflies also excrete honeydew, which imparts a shiny and sticky sheen to leaves, encouraging the growth of sooty mold fungi. The whiteflies flutter about before settling again when disturbed plants are infested with whiteflies.
Whiteflies are controlled by spraying the plant thoroughly with insecticidal soap, especially the lower leaf surfaces. Imidacloprid plant spikes are also used in the soil to control whiteflies. Whiteflies can be controlled by spraying products like insecticidal soap, neem oil extract, imidacloprid, acetamiprid, cyfluthrin or permethrin on houseplants that are taken outside.
Less Common Pests
Thrips
Thrips are small, slender, black and yellow insects that have fringed wings. They usually appear on leaves and between flower petals. Almost invisible to the naked eye, the adults are barely 1/16th inch in length. Blowing lightly into blooms and leaves causes thrips to move rapidly, making them easier to see.
The larvae and adults of the thrips feed by scraping the cells on leaves to suck the sap. The damage caused by thrips to leaves is similar to that caused by mites.
Feeding by thrips on flower buds can kill flowers before they open. The flowers may be streaked or distorted as a result of the feeding.
To control them, wash plant foliage with water, spray it with an insecticidal soap, and spray outdoor houseplant foliage with thrips poison. A plant with flower buds infested with thrips must have a systemic insecticide that can control the hidden thrips, such as spinosad, acetamprid or imidacloprid.
Springtails
Springtails are tiny insects about 1/5-inch long, usually black or white, that live in the soil. They have no wings, but can jump. Their presence indicates overwatering.
In addition to eating decayed organic matter, springtails will also chew on tender plant parts such as seedlings. The damage is usually small but quite nuisance when in large numbers.
To control this condition, most plants can withstand it by allowing the soil to dry between waterings.
Leafminers
A wide range of different insects, called Leafminers, are young worm-like stages that feed between upper and lower leaf surfaces. The damage from Leafminer pests appears as a winding, discolored trail or irregular blotches within the leaf. Although these pests are unsightly, they rarely cause serious damage.
Remove and destroy any leaves with leafminer damage. Sprayers with foliar systemic activity such as acetamiprid, imidacloprid, or spinosad help. Imidacloprid plant spikes in the soil also work well.
Beetles
There are several species of aphids and their larvae that feed on house plants. They may enter through a home’s openings when house plants are brought inside toward the end of the summer, or through openings that are merely inaccessible.
Get rid of the beetles. If they return again and feed on plants outside, spray with neem oil extract, imidacloprid, cyfluthrin, or permethrin to control them for one to two weeks.
Caterpillars
A caterpillar varies in size from about 1 to 2 inches in length. It is a larval stage of butterflies and moths. The species vary in color with most of them having a gray, brown, or green color, as well as mottled or striped patterns. These creatures are usually smooth, or may have spines, hairs, or bumps along their bodies.
The eggs of many butterflies and moths are laid on the undersides of leaves on plants which have been outdoors. Occasionally, stray moths that have found their way into the home will lay eggs on houseplants. A caterpillar can start as a quite small caterpillar, but will grow with every molt (a process where the skin is shed) it undergoes.
A caterpillar’s mouthparts allow them to feed by swallowing leaves, buds and flowers. Some caterpillars eat large amounts of the plant within relatively short periods of time, while others drill into stems for food.
Caterpillar droppings (fecal pellets) on leaves and beneath plants indicate that caterpillars have caused the damage.
To get rid of caterpillars and their eggs, remove the plants outside. Then spray them with an insecticide.