You know the clouds of tiny flies that appear whenever you move your houseplant, or the little critters that nest in leaf nodes or create webs on the bottom of the leaves?
This can be one of the most common houseplant pests, and it becomes more noticeable in the winter when it is too cold to be outdoors.
“If you think you have a pest infestation of any kind, have a hand lens or magnifying glass handy, because many of the life cycles of these creatures are difficult to actually see,” advises houseplant expert and host of the On The Ledge Houseplant Podcast. . Jane Perrone, author of Houseplant Gardener In A Box (Skittledog, £19.99).
Here are five of the most common houseplant pests you may encounter and how to deal with them.
1. Fungus mosquito
These clouds of tiny black flies, also known as sciarid flies, are one of the most annoying houseplant pests, but they don't actually cause any significant damage to your plants because they only feed on the decomposing matter of fungi in the soil, Perrone says. .
Their real appeal is their moist compost. Like houseflies, they lay eggs on the ground, producing larger numbers.
Solution: You can catch gnats by storing compost in a dry place or placing sticky yellow traps in the soil (or on the soil surface), suggests RHS senior horticulturist Guy Barter. They will hold up better using composted houseplant mix rather than peat-free potting media, he adds.
“The gold standard treatment is to apply biological control twice a year, in spring and late summer or fall,” advises Perrone. There are microscopic nematodes, which you can buy in powder form, mix with water according to the instructions, and then apply the solution to the soil. “For the treatment to be effective, the soil must be moist,” she adds. You can buy them online from stores like Ladybird Plantcare or Dragonfli.
Another solution is to place carnivorous plants, such as pinguicula (butterwort), next to the infected plants. These plants have sticky leaves that can trap fungus gnats, suggests Tony Le-Britton (@notanotherjungle), home plant expert, influencer, and author of Not Another Jungle. (DK, £16.99).
2. Aphids
These are very common, appearing mainly on stems and sap-sucking tender new growth, and reproduce incredibly quickly. They tend to prefer plants that are overly stressed, so the better you care for your houseplants, the less likely they are to suffer damage, advises Barter.
Solution: Houseplants are easy to control. Remove them by pricking them with your finger and thumb, or use a soap-based insecticide that has been tested on a variety of plants and is compatible with organic protocols.
3. Thrips
These very small, light to dark brown critters, about 2 millimeters long, are becoming one of the most common houseplant pests, says Le-Britton. They attack the leaves, sucking out sap and depleting energy, causing yellow spots on the leaves. They are difficult to eradicate because they lay eggs inside leaf cells and are invisible. Susceptible plants include philodendron.
If you look at the underside of a leaf with a magnifying glass, you can see tiny rice-like creatures moving around, Perrone adds.
Solution: The best way to deal with this is to physically remove it. When you water your plants, shower the entire plant, then wipe the leaves with a damp microfiber cloth, Le-Britton advises.
“There are biological control methods you can use, but the first thing you need to do is separate your plants from other plants and check your other plants because thrips spread from plant to plant. “Repeatedly cleaning the leaves with a horticultural soap spray will help solve the problem,” says Perrone.
4. Mealybugs
Commonly infesting succulents such as cacti, monstera, and aloe, these bugs look like tiny, furry wood lice that hide in every nook and cranny of the plant and under the leaves, appearing all over the plant.
“By the time they do that, they’ve almost certainly infected an inaccessible root ball, and that’s usually the end of the plant,” warns Barter. “They suck out the sap and leave behind a lot of honeydew, which makes the plant sticky and dark and covered in this white poop.” They are commonly found in orchids. “Unfortunately, there is no pesticidal option,” he adds.
Solution: “We have had some success using commercially available nematode mixtures to kill a variety of insects. Otherwise, discard the plant as it can infect all your other plants fairly quickly,” adds Barter.
“If you see fluffy white areas on your plants, the first thing to address is because they are nests where the adults lay their eggs. Get a cotton swab and rubbing alcohol (surgical alcohol) and dab the area,” suggests Perrone.
Le-Britton recommends physical removal to reduce numbers.
5. Spider mites
You'll need a magnifying glass to spot these tiny round red, brown or white mites, which look like blobs, but they multiply quickly, leaving white pellets near the central ribs of leaves and, if infestations are severe, visible spider webs. Again, they are sap-sucking plants and plant symptoms include browning and yellowing of leaves and stems. They like large, flat, dry surfaces, so they prefer plants like calathea and alocasia, Le-Britton says.
Solution: Shower dry leaves regularly to keep their numbers down, or wipe the leaves frequently with a clean, damp cloth, he suggests.
“There is no one-size-fits-all solution for every pest that you can do or apply to your plants. Because problems are forever flying through the window, bringing new plants, new plants. In the soil, we have to fight a war of attrition,” Perrone concludes.