Common Houseplant Pests and How to Treat Them
Whoop whoop! It’s finally Spring and although we are LOVING seeing the sunshine and a surge of new growth on our plants. Unfortunately, it is also this time of year that we tend to see some familiar villains - pests!!
Perhaps you’ve noticed brown spots or nibbled edges on the leaves of your houseplants, or even witnessed some insect activity around the soil of your plant. If so, there’s a good chance that what you’re noticing is down to pests.
If you're new to indoor plants, it's important to remember that finding pests is not a sign that you've done anything wrong! Pests are a very natural occurrence and while they most commonly sneak in via nurseries, they can also literally blow in on the wind! The good news is, that once identified, most common houseplant pests are actually very easy to treat without the need for expensive or potentially harmful chemical cures.
In the following sections we’ll outline how to identify and treat the most common houseplant pests and wrap up with a few prevention tips to stop you ever needing to battle with them again.
Spider Mites
Image: Scot Nelson, via Flickr.
Discovering these little blighters have taken up residence on your favourite plant can seem like a real cause for concern, but thankfully they are relatively easily treated once identified. The first thing you’ll need to look for is a fine webbing that often appears at the base or underside of leaves, particularly if they have any curling or texture to them. If you notice this, be sure to carry out a thorough check of the plant. Look for any clusters of brown or red coloured dots. If you do see these, then it’s definitely a good idea to treat the plant.
A lot of sources will advise the use of a horticultural oil such as Neem oil for the treatment of Spider Mites, and while that is absolutely a viable method of eradication of these pests, I prefer a simpler alternative that you're much more likely to have lying around the house!
Mix together a small amount of mild liquid soap (dishwashing soap is fine) with water in a spray bottle for easy application. A general rule is one teaspoon of soap to one litre of water. Spritz generously all over every leaf and the stem of the affected plant. Then, use a clean cloth to gently but thoroughly wipe down both sides of each and every leaf, clearing any visible critters, eggs or debris that’s sitting on the leaf surface. Repeat this process three times over the course of a week, and you should find yourself free of the mites.
Mealy Bugs
Image: Gailhampshire, via Flickr.
To identify these little beasts, look out for small, white, cotton-like clumps appearing on the leaves. You should also look for the strange dew-like residue they’ll leave in blobs on the leaves, and sometimes you’ll find living bugs crawling over your plants leaves and stems.
As with the Spider Mites, you’ll need to clear the foliage of any living critters as well as their cotton houses, eggs and residue (gross)! Use clean water and clean cloth to wipe down the leaves and stems and remove all visible evidence of the bugs. Any smaller bugs that are proving difficult to remove, you can use a cotton-bud dipped in methylated spirits to dab onto them - this will stop them in their tracks.
Aphids
Image: Peter & Michelle S via Flickr.
These small, wingless insects reproduce rapidly and if you spot one, you can almost guarantee you’ll find a cluster of them next! They suck the sap from the leaves and stems of the plant and can cause significant damage if left untreated.
To eliminate a population of Aphids, you can simply dislodge them with a jet of cold water, or for a more sure-fire treatment, I like to use the same liquid soap mix as described above (for treatment of Spider Mites) to blast them away. Apply the soap mixture three or four times over the course of a week and you should see the Aphids disappear hopefully never to return!
Fungus Gnats
Image: Andy Murray via Flickr.
If you’ve noticed tiny little flies buzzing around the soil of your plant, particularly if you move the pot then there’s a decent chance that these are Fungus Gnats. These little demons will chew on your plants roots and wreak havoc if not treated.
The best way I have found to combat these critters is actually to allow your soil to dry for a while. Basically the larvae of these gnats can’t survive without moisture, so if you give your soil a chance to dry out then you’ll inhibit the growth of the larvae, ultimately breaking their reproduction cycle and ending the population of gnats occurring in your plants’ soil.
Alternatively, you can apply a soil drench with horticultural oil such as Neem oil. This is a botanical insecticide that you dilute in water and apply directly to the soil. If you do choose to use this method, be sure to follow all the manufacturers instructions carefully as insecticides can be harmful if used improperly.
Prevention
Unfortunately, pests are an inevitable part of keeping plants indoors but armed with the right knowledge on how to identify them, treat them and ultimately get ahead of them (i.e. prevent them occurring in the first place) you are well-placed to beat the little beasties!
My first advice for prevention, is to quarantine any new plants you bring into your home. I know, just the word ‘quarantine’ sends chills down your spine after the year we’ve had (thanks COVID!!), but honestly, if you do have a space that is set apart from any other plants, it’s worth sitting your new plant there for 2-3 weeks before placing it close to any other precious foliage. Although nurseries do usually treat for pests, some slip through the cracks and don’t become obvious until they are in your home. Most of these insect pests have a pretty short life cycle, so 3 weeks should be ample time to allow for any critters to reveal themselves.
Second up, get a regular maintenance schedule down. A regular and appropriate watering regime as well as making sure light levels are in check is a must. During this time, i.e. as you are watering, take a moment to closely check the foliage for any signs of damage or insects, inspect the soil and remove any spent flowers or leaves.
Finally, if you’re dealing with tropical foliage such as Fiddle-leaf Figs, or palms, a regular misting not only benefits the plant by making it feel right at home, but a humid environment also inhibits the hatching of Spider Mite eggs preventing them from populating your plants.
All the best with your pests - BB x
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If you're interested to learn more, or seeking further tips, we'd highly recommend this Gardening Australia segment.