Houseplant pests, part 1
Updated: May 30, 2022
When I say the word “bug” I can see the fear in the plant owner's face. I know people hate when I say this but when you own plants, you WILL deal with bugs eventually. Bugs love plants. They just do. They depend on these hosts to survive. Nonetheless, bugs don’t have to scare you. You just need to understand them. In the first of this two-part series on pests, I will explain how bugs get to our plants in the first place and cover identification and treatment for one common pest, spider mites. The second post will cover several other common pests.
First, let's talk about one way houseplants get bugs in the first place. I hate to be the bearer of bad news but it would be nearly impossible for a grower to deliver plants to a retailer pest-free. Growers treat for bugs but can’t guarantee to catch everything. Almost every time I'm browsing the garden section of a big retailer I see at least one plant infested with pests. When one solitary, tiny bug is left, it will multiply until the plant is infested. Yep, that's bugs. It stinks and I hate for plant lovers, but it's the cold, hard truth. This is why I do my best to ensure that the plants I sell do not introduce pests to your home. Every time I receive a shipment of plants from growers I bring the plants into my greenhouse and inspect them. I then spray my whole greenhouse with commercial pesticides. Depending on the bug I find, I may treat the plants multiple times. Once I have brought the new plants into my shop I spray with horticultural oil once a week. It's safe to spray indoors and doesn’t smell awful.
Me, treating my inventory
Now, even though you may buy a plant that is bug-free, it will likely not stay bug-free forever. Bugs are inevitable. However, not all bugs are bad. It's very important to identify the bug and determine what course of treatment to take if one is necessary.
My go-to source for identifying and understanding common houseplant pests is a site called Featured Creatures. The site is maintained by the University of Florida's Entomology and Nematology Department and the Florida Department of Agriculture and Consumer Services' Division of Plant Industry. These guys know their stuff, and because Florida grows most of the houseplants sold in the United States, these guys know the stuff that matters most to us. The Featured Creatures site is excellent, but its breadth and depth may overwhelm most plant lovers. Here I will summarize what I've learned about one of the most common houseplant pests you are likely to encounter.
Spider mites: the bug
These are my arch-enemy because they take the most work to eradicate. There are different varieties of spider mites but they usually appear either red or translucent yellow. They are very small and may be too difficult to see with the naked eye. I use a hand lens (that thing the jeweler uses to look at diamonds) when I want to be sure.
Denmark, H. A. “False Spider Mite.” A False Spider Mite - Brevipalpus Californicus (Banks), University of Florida, Nov. 2015, https://entnemdept.ufl.edu/creatures/orn/mites/Brevipalpus_californicus.htm.
Spider mites: the damage
These critters may be too small to see clearly with the naked eye. You can use a hand lens to see them, but perhaps a better place to start is looking for signs of them in the form of leaf damage or webbing. However, I’ve found that many people mistake spider webbing for spider mite webbing. Mite webbing will cover the leaf and is accompanied by leaf damage. The best way I can describe this leaf damage is that it looks like the chlorophyll is being sucked out of the plant. You may also see yellow spots in a damaged area. Spider webbing, on the other hand, may be more indiscriminately spread around the plant and will not be accompanied by leaf damage like this.
Spider mite damage and spider mite webbing
Denmark, H. A. “Twospotted Spider Mite.” twospotted spider mite - Tetranychus urticae Koch, University of Florida, Dec. 2019, https://entnemdept.ufl.edu/creatures/orn/twospotted_mite.htm.
Spider mites: the treatment
So what should you do if you see spider mites? Take your plant outside and blast it with a water hose (alternatively, you can do this in the shower if you prefer). The goal is to knock as much of the webbing, pests, and eggs off as possible. Let your plant dry off back inside. Cut back any severely damaged leaves. I've even gone so far as to cut a plant back completely, to the point where no leaves are left. Spray it down with horticultural oil. Then wipe each leaf down with paper towels on each side. Spray it again with horticultural oil. Repeat the process of spraying and wiping down leaves every three days for a month, keeping the plant quarantined from the rest of your houseplants until the process is finished.
This process has worked for me many times. I know this sounds like a lot, but mites are the hardest pest to treat. This is why an ounce of prevention is worth a pound of cure.
Although spider mites can be common and difficult, there are several other pests you need to know about. I'll cover those in a follow-up post. Thank you for reading! Always feel free to contact me with any pest questions.