To be a gardener means dealing with growth and decay, and inevitably bugs. We all know how important insects are to the environment in general, but there are a few of them that can do much more harm than good if they find their way into our homes and gardens.
What is a plant pest?
Merriam Webster tells us that a pest is a “plant or animal detrimental to humans or human concerns (such as agriculture).” The most common examples of these detrimental animals you’ll come across as a gardener or houseplant collector are:
Fungus Gnats: tiny flying insects that resemble fruit flies, whose larvae live in the soil and feed on the roots of plants.
Mealy Bugs: white insects in the scale family, which some of us think resemble ancient fossilized sea creatures when viewed up close, but which tend to form clusters of fuzzy cottony clumps.
Scale: small, usually brown or black creatures which attach themselves to a plant and form a helmet-shaped shell around themselves for protection while feeding on the plant’s juices.
Spider Mites: being no bigger than the period at the end of this sentence, a single spider mite is very difficult to see with the naked eye. What you’ll notice first is the webs they build, usually on the underside of leaves.
Aphids: generally found in the garden, these soft-bodied and colorful insects are very good at blending in with whatever plant they are feasting on.
Whiteflies: these tiny moth-like bugs which feed on plant sap are not actually flies, but more closely related to aphids. Their rows of yellowish eggs are usually easy to spot on the underside of leaves.
Thrips: tiny brown or black insects with long bodies and fringed wings. They can be hard to spot, but you’ll notice evidence of their presence– pale white/yellow scratchy spots on leaves and black specks of excrement.
Where do they come from?
As there are roughly two hundred million insects for every individual human being on earth, it’s no surprise that some of them will manage to sneak into our living spaces. But it doesn’t make it any less frustrating when we discover an infestation that seemingly came from out of nowhere. Understanding where they tend to come from can help us prevent future unwanted visitors.
New plants: One of the most common culprits are those new plants you just bought. Though most plant shops and nurseries regularly inspect and treat their inventory for pests, it’s a good idea for you, the customer, to also take a careful look for bugs before buying any plants. Once you get them home, it’s easy for most insects to spread from one plant to another, especially if it’s a type they have an appetite for.
Summer vacation plants: Most tropical houseplants would enjoy spending the warmer months outside, (though sheltered from too much direct sun). Heat and humidity are two things they love, but which are lacking indoors. If you have the space to move some of your plants outside during the summer, excellent! But when it comes time to bring them back inside, it’s necessary to check for bugs and hose them off or otherwise treat them.
Fresh produce: Though it may seem far-fetched, it’s perfectly normal for a few critters to be lurking in the leafy produce we bring home from the store or the farmers’ market, especially if it’s organically grown and untreated with pesticides.
Open windows: The holes in screens are no match for tiny fungus gnats, aphids, and white flies. Even spider mites, which don’t have wings, can easily catch a ride on a summer breeze straight through your window. So keep a close watch on your indoor windowsill plants during open-air season, especially if there are other plants right outside.
Bags of potting soil: It happens rarely, but it’s possible for insects to take up residence in unopened bags of potting mix, especially fungus gnats. Inspect your soil after opening it– if fungus gnats are present, you’ll notice them flying around. Any reputable garden center will refund or exchange your purchase, though you might consider trying a different brand next time.
Cut flowers: Like with produce and other organic material, we should not be surprised to find the occasional hitch-hiker hidden among the leaves and petals of fresh cut flowers. This is more likely to happen with organically grown flowers, as most mass-market floral products have been treated with various pesticides.
Stressed Plants: Like people, plants get stressed out too. This can happen if the sunlight is too harsh or not enough, watering is infrequent or too much, or the plant does not have the correct amount of nutrients. If a plant is unhealthy or stressed, it sends out signals that it is unhappy. Pests pick up these signals and gravitate toward the plant.
How do I get rid of them?
Before any kind of treatment, it’s recommended to separate your insect-infected plants from any healthy ones, to prevent them from spreading.
Fungus Gnats thrive in moist soil, so the most basic step you can take to prevent them from taking over is to let your plants dry out a little bit more between waterings. Yellow sticky traps are an effective way to get rid of the adults. In addition, a thorough spraying of Neem oil onto the soil (best done after watering, when the gnats come to the surface) will usually do the trick. “Mosquito Bits” or beneficial nematodes are products which can be mixed into the soil, killing the larva.
Mealy Bugs can be easily removed with a Q-tip dipped in rubbing alcohol, though they are very good at hiding, so be very thorough when you are conducting a search-and-destroy mission. Additionally, you can spray the plant with an insecticidal soap or a homemade recipe of 1 tsp dish soap mixed with 1 liter of water. Check back every few days to see if any bugs have returned.
Scale, like mealy bugs, can be removed with rubbing alcohol, although you might need something with a bit more force than a Q-tip– a plastic spoon or a guitar pick both work quite well. Again, you’ll want to follow up with a spray of Neem oil or insecticidal soap to rinse off any leftover loose bugs. And keep your eyes peeled for any survivors that appear over the next few days.
Spider Mites are attracted to dry environments, so using a humidifier or a misting bottle can be good preventive measures, especially if you’re growing the spider mite’s favorite plants like Croton, Alocasia, or Hedera (ivy). If they’re already established, an insecticidal soap which contains Pyrethrin is recommended. Unfortunately though, spider mites are one of the most persistent and difficult-to-defeat pests, so if your plant is seriously infested and really struggling, you might just consider disposing of it and starting over with a new specimen.
Aphids are generally found in the garden, where you don’t necessarily want to go crazy with insecticidal sprays (think of the butterflies and bees!). Ladybugs and Lacewings are great natural predators for aphids, and can usually be purchased at garden centers in the spring and summer. Also, a regular blast from your watering hose can go a long way in keeping your plants aphid-free.
Whiteflies can multiply very quickly, so it’s advisable to treat any sightings as quickly as possible. Thoroughly spraying the leaves (especially the underside) with Neem oil or an insecticidal soap generally takes care of the problem, but check back weekly and re-spray if necessary.
Thrips can be washed off with a simple spray of water, but a close eye should be kept on the plant to see if they return. Blue sticky traps are also effective to trap them. If they persist, an insecticidal soap containing Pyrethrin can be used.
Am I a bad plant parent if my plants have bugs?
Not at all! Every plant enthusiast will come into contact with one or more of these pesky bugs eventually. That being said, sometimes giving our plants too much TLC can also attract more pests. Fungus gnats thrive on plants that are over-watered and never dry out. Plants with high nitrogen levels, which can be caused by over-fertilizing, are especially appealing to scale and mealy bugs. At the end of the day, every infestation is an opportunity for education!
*** Whenever applying an insecticidal soap, Neem oil, or other oil-based spray, do it at a time when the sun is not shining on the plant, as this can burn the leaves.
*** Always read the directions and safety warnings completely before using any store-bought insecticides.