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General Prevention

There are an estimated ten quintillion individual insects on the earth. So it is not a surprise that some of them end up inside of our houses. Most of these insects are harmless to our houseplants, but specific types of insects have piercing mouthparts designed to feed on plants. These pests drink sugary juice out of leaves and stems, much like drinking from a straw.

There are many ways to treat pest infestations on your houseplants, but some even more useful practices are those that can prevent an infestation from ever occurring. First off, make sure to inspect your plants regularly. When you water your houseplants, take a look at the soil and underside of the leaves. Keeping a close eye on your houseplants can help to catch any insects before they reproduce. Similarly, inspect any new plants you bring into your house. Horticultural retailers work hard to prevent pests from living in their greenhouses, but it can occur. If you notice any insects on a new plant, you should contact the seller to alert them about the problem, as they will want to treat their growth facilities. You should also keep the plant isolated from your other houseplants to prevent the pest from spreading. Separating new plants is an excellent practice to follow even when you don’t see any insects. As we will later outline, some of these pests can be very small and easy to miss. Similarly, try to allow some space between each plant. By spacing your plants slightly apart, you can create a barrier against inter-plant insect travel.

Pesticides

There are various treatments available to remove insects and pests from your houseplants. The term pesticide is very broad and refers to any application that can kill insects, weeds, fungi, bacteria, or even mice. By definition, it doesn’t tell you anything about the chemical composition or how safe it is around people or pets. We’re going to break down the different types of pesticides and approaches used during pest management. 

Traditional Pesticides

Traditional chemical pesticides are rarely used on houseplants due to these plants’ proximity to humans, pets, and food. Instead, there are less-toxic alternatives that we recommend utilizing first. 

Insecticidal Soap and Neem Oil

Insecticidal soaps and oils are commonly used indoors. Insecticidal soaps can be purchased or mixed up at home. You can make a concentrate with 1 cup of cooking oil and one tablespoon of fragrance-free dish soap. Mix 2 teaspoons of this concentrate vigorously into a cup of warm water. The application of this soap can be sprayed or wiped across the leaves.

Neem oil, an oil extracted from neem trees, can be used to create insecticidal oil. Mix 1 tsp neem oil, ½ tsp fragrance-free dish soap to 1 quart of water, and mix well. This mixture can be sprayed or wiped onto the leaves, and after a few hours, you can wipe any excess off.

Both insecticidal soap and oil kill insects by interacting with their protective coatings; for this reason, both are best applied in the evenings, when beneficial insects are less active since we don’t want to hurt them. Insecticidal soap and oil, when dilute, are non-toxic to people and pets.

Water and Alcohol

You can remove most adult insects and eggs off plants by merely using a garden hose with moderately high water pressure to blast off them off. If you have more delicate plants, you can also dip it upside down into a bucket of water and gently swish it around.

Infestations that form visible clusters, like mealybugs, can be spot-treated with a cotton swab dipped in 70% rubbing alcohol. It’s best not to use alcohol over a large portion of the leaf. Alcohol kills bacteria, viruses, and insects by drying out their surfaces. Likewise, alcohol also dries out the leaves’ surface, so it shouldn’t be your first choice for a pesticide.

Beneficial Insects:

Beneficial insects are often used in industrial settings. The use of beneficial insects in the home has increased as plant owners have become more interested in utilizing natural products to protect their houseplants. Many online services sell helpful insects such as ladybugs and green lacewings. These useful insects arrive as juveniles or eggs and are simply added to your plants. The first few days can feel a little strange, as your new insect friends will move around your house looking for a good place to settle. But upon discovering the insect pests, they will quickly land in your houseplants and get comfy munching on your problematic insects. These beneficial insects won’t bother your house plants, and once they have eaten all their prey, they will stop reproducing and die off. 

Identification and treatment

Fungus gnats 

A typical household pest is the fungus gnat. Although harmless to your houseplants, these annoying insects can quickly make your home a less than ideal place to relax. Fungus gnats are similar in size to fruit flies. These pests lay their eggs in damp, wet soil. There, the juveniles feed on fungi. You might notice fungus gnats when you disturb your plants. The adults will fly out of the pot for a few seconds before they settle again. You can help prevent this by using well-draining soil and not overwatering your plants. Remember to remove any plant debris that may drop onto the surface of your soil, as this can encourage fungi growth. Fungi prevention can include traditional pesticides or more natural remedies. For example, cinnamon has anti-fungal properties, and when sprinkled on the surface of the soil,  can help reduce fungi, thus removing the food source for the gnats. Adult gnats can be trapped on yellow sticky traps. 

Thrips 

Thrips are tiny flying insects that grow to only 1/5th of an inch. These pests look like specks moving along the leaf veins. Infested plants will have brown or silver lines of discoloration on the leaves, which will eventually turn yellow. Newly emerging leaves might even be misshapen. Thrips will feed on any available plant but have a preference for African violets. Thrips are attracted to the color blue and can be trapped on blue sticky tape. To remove eggs and juveniles, wash your plants with a garden hose. Natural predators such as cucumeris mites (Neoseiulus cucumeris) can be purchased and released onto your houseplants. Insecticidal soaps and oils can be used as a treatment on leaves. As a last resort, thrips can be treated with traditional pesticides such as those containing a type of chemical called "pyrethrin".

Common brown scale 

Scale is a term that encompasses several insects that all share similar characteristics. The most common type, brown soft scale, is caused by insects in the Coccidae family. Scale can be found on leaf veins or along the stem. Because scale is a small insect that can hide well, the earliest signs of scale are often a sticky, shiny residue found on the leaves. This secretion, called honeydew, is released by the insects as they consume sugars from the plant. 

Found on Ficus, umbrella plants, and citrus, scale can be challenging to notice. Adults give birth to live young, that are free to move about the plant. These juveniles are known as “crawlers.” Once situated on a nice, juicy vein, the crawlers puncture the plant and become immobile. Immobile adults are ovular and can reach 3-4 mm in length. Their backs are covered in shell-like armor, thus giving them their name. These scales can be brown to dark yellow. Scale infestations can lead to the premature death of the lower leaves and plant die-back or stunting. 

Scale is a treatable insect, although it can take repeated applications to ensure full annihilation of the adults and “crawlers.” First, begin by covering your soil with plastic. This ensures no stray eggs fall into the soil where they can hatch again. Remove as many insects as you can with your fingers. They can be pried off with your fingernails and are harmless to humans. Then apply insecticidal soap or oil to the upper and lower portions of the leaves and stems. You might need to repeat this process several times over a few months. 

Mealybugs 

Similar in appearance to scale, mealybugs are small ovular insects that suck sugar and nutrients from leaves and stems. Some significant differences exist between scale and mealybugs. Mealybugs are unarmored, making them easier to kill with pesticides, but they are also very mobile, making it more difficult to halt their infestation. If your plants are touching at all, the potential for mealybugs to spread is highly likely. Mealybugs have an incredibly fast-paced life cycle. A single female can lay up to 600 eggs. These eggs mature after four weeks, leading to a new wave of bugs. If left untreated, this can quickly overwhelm a plant. 

Mealybugs are easily identified by a white, sticky, cotton webbing that they create around themselves as they feed. If identified, a cotton swab dipped in rubbing alcohol can be used to spot-treat the cluster of insects. Alcohol quickly kills any mealybugs that it contacts, but it also dries out your plant, so use this only as a spot treatment. For overall treatment, you will need to combine a few different control techniques. Because mealybugs are mobile, they can hide in tiny grooves and crevices. This can make pesticide application less effective; beneficial insects are the best control for mealybugs! Ladybugs, mealybug destroyers, and green lacewings can be purchased online. All of these species eat mealybugs and can get into tight spaces where mealybugs hide. This, in combination with an alcohol spot treatment, should be adequate to end your mealybug problem. If not, the use of insecticidal soap and oils can be used when needed.

Aphids 

One of the most well-known pests is the aphid. Although it is more commonly found on vegetable plants, aphids are opportunistic and willing to feed on any sugary plant, with a houseplant preference for Orchids. There are over 5,000 different species in the Aphid family. Because of this, the exact color and size might vary, but all adult aphids are teardrop-shaped and about ⅛ inch in length. Aphids use sucking mouthparts to feed on plant sap, and in doing so, release honeydew. Aphid infestations cause leaf wilting and curling and even damage to flowers. Aphids are soft-bodied and generally wingless, making them a less daunting pest than others. If your houseplant is sturdy, use a garden hose outside to blast the insects off. If your plant is more delicate, try dunking the plant’s leafy parts in a bucket of water for a few minutes. Any remaining adults can be picked off by hand. Green lacewing and ladybugs can be used as beneficial insects to help finish off stray aphids. Like always, insecticidal soap and oils can be applied to the foliage.

Common whitefly

 

Whiteflies are a winged houseplant pest. These insects, which can be easily confused with small white moths, can cause stunting and yellow leaves as they suck nutrients from your plants. Adult whiteflies are excellent multitaskers, able to lay eggs and eat at the same time. Plants with whitefly may show honeydew residue on the leaves, and when disturbed, the adults will fly up into the air. Whiteflies have developed resistance to many traditional pesticides, so the best treatment for these pests is through more natural avenues. Eggs and juveniles can be removed from leaves by washing the plant with a hose. Adults can be trapped on yellow sticky traps. Also, beneficial insects like ladybugs and green lacewings can be used to eat the remaining insects. 

Red spider mites

Spider mites are more closely related to spiders than to insects but still feed on your houseplants. These tiny creatures are practically microscopic, making them a challenging pest to prevent entering your home and even more difficult to remove once they have arrived. Under a magnifying glass, spider mites have red or yellow bodies and eight legs. To the naked eye, this may look like a faint reddish speckling on your leaves. Eventually, these mites form a thin webbing, usually on the undersides of leaves. Like the other insects, mites suck sugary nutrients from your plant, leading to yellowing and wilting. Because spider mites are so small, they can be challenging to remove manually. Spider mites prefer dry air; you can make your environment less suitable for them by placing your plants near a humidifier. Use a hose to wash off as many mites as possible, and then using beneficial insects, like the green lacewing, and insecticidal soaps to eradicate the remaining.

 

Despite the vast array of pests that enjoy eating leaves, a houseful of healthy and happy plants is easily possibly with a little extra care!