Health is wealth

Yes prevention is better than cure, but when you need the cure, these simple steps will help you heal your houseplants and give them what they need to thrive.

Kept indoors, plants tend to get fewer pests than outdoors, but bad bugs can be a year-round problem for houseplant hobbyists. Going by the cries for help on social media indoor plant groups, sadly mirrored in my own experiences, this year’s been a particularly bad one for mealybugs and fungus gnats.

Those are two of the most common pests that plague indoor jungles. I’d reluctantly add spider mites and aphids to that list also. Having gone to war with them all over the years, here’s what I’ve learned works best for no pests and no panic, from home remedies to bringing out the storebought big guns.

But before you buy or DIY and launch the attack, do a test treatment first. And yes, that includes testing natural and home remedies too, as I learned the hard (and sad) way, having burned my beloved Begonia Angel Wing’s leaves by using too much organic neem oil. Some plants are more sensitive than others. The point here is to kill the pests – not your plant.

If you know your plant is on the sensitive side, pick a small area to treat first, at least a couple of days before the rest of the plant. Some plants are sensitive to oil-based treatments, more so if the plant is also water-stressed.

Watering before treatment is recommended. For most treatments, you also want to keep plants out of direct sunlight or turn grow lamps off while treatment’s still wet on leaves.

Pest prevention

I’ve learned the value of pest prevention the hard way. I naively thought I’d magically manage to keep my indoor jungle pest-free. Of course, the inevitable happened. Since starting my plant parent journey, I’ve ticked all the most common bugs off the list.

Although keeping plants healthy is a good preventative in general, there are two things I now do differently when it comes to bugs: isolate new arrivals, no matter where the plant’s come from; and silica.

Many common pests complete their lifecycle within four weeks, so I keep new jungle members in quarantine away from the rest for at least a month.

Those more pest-prone get a preventative treatment on arrival. For the rest, it’s a matter of wait and see with a thorough inspection after the month is up before they join the rest of the jungle.

My other secret weapon has been silica. The silica in soil water is nature’s way of protecting plants from pests outdoors, but indoors our houseplants miss out. Silica makes plants stronger, both physically and by supporting stronger defences against pests. The one I use is called GT Silica but there are other brands easily available.

All are best used little and often, every time you water.

Mealybugs

Mealybugs are small white crawling bugs. At 3-5mm, adults are visible to the naked eye, but don’t let their soft appearance fool you, these are the fluffy vampires of the plant world, literally sucking the life out of your plants.

I would not want to play hide-and-go-seek with mealybugs. They are very good hiders so can be easy to miss at first. Early signs start with white powdery, cottony deposits hidden in plant crevices. Once they mature, adults are easy to spot as they treat your plants like an all-you-can-eat buffet. They prefer to feed on tender, new growth of leaves, buds and flowers.

Mealybugs also excrete sweet honeydew, which attracts ants and can lead to the growth of black sooty mould, a type of fungi.

As with any pest, the first step is to panic. Just kidding (sort of).

The real first step is to immediately isolate the plant, then check for pests on the rest of your jungle, especially those nearby. I keep plants isolated for at least another four weeks after all signs of pests are gone.

Being a type of scale, the treatment for mealybugs and scale are the same. Protected by a powdery wax that repels water-based insecticides means common insecticide treatments aren’t always effective on mealybugs.

The next step is to grab the alcohol – not for you, for the

Although keeping plants healthy is a good preventative in general, there are two things I now do differently when it comes to bugs: isolate new arrivals, no matter where the plant’s come from; and silica.

bugs. Alcohol gets through that waxy layer for instant kill on contact. You want rubbing alcohol, which is usually around the 60-70% level, not 100% alcohol. Easy to get from hardware stores and chemists.

The problem with mealybugs is killing the adults is just a blip in their lifecycle, and before long they’ll be back – well, their next gen anyway – with a vengeance. The secret is a one-two punch of a contact insecticide and systemic insecticide together. My secret weapon is a systemic called Groventive, made by Kiwi company Grosafe.

Both alcohol, or another contact insecticide option made by Grosafe called Enspray 99, work on the outside as a contact insecticide for instant kill. Groventive works from the inside to stop them coming back and reinfesting your plants, very common with mealybugs if you only use a contact insecticide.

Dip a cotton bud, makeup wipe or similar in rubbing alcohol and touch that to every adult you can find. They will die instantly, turning orangey-brown. Once you've wiped off visible adults, spray the plant thoroughly with one part rubbing alcohol and one part water, adding a few drops of liquid dish soap to break through that waxy waterproof coating. Pure castile soap is best. I use a brand called Dr Bronners.

Get everywhere, under and over leaves, and don’t forget the pot and saucer. You want a fine-mist sprayer for better coverage. I’m weirdly obsessed with my Mister 360 spray

The problem with mealybugs is killing the adults is just a blip in their lifecycle, and before long they’ll be back – the next gen anyway – with a vengeance.

mister for pest treatments as it even sprays upside-down.

Although optional, I recommend repotting. Mealybugs are great hiders. If you want to do everything possible to make sure they don’t come back, repot into new soil, spraying the pot and saucer too. I use Oxygen Plus for a quick clean-and-kill at the same time.

This last step is one I would not skip. Use a systemic to break the cycle so they don’t come back. My go-to is Groventive. Best mixed with Enspray 99 to make the spray finer and to keep Groventive on the leaf surface longer. Although one treatment is normally enough for other pests, for mealybugs two is recommended.

Spider mites

You’d need your spidey sense to spot these pests. They’re less than 1mm in size and usually hide out under leaves. Although you’re unlikely to see them without the help of a magnifying glass, there are telltale signs you can watch out for.

In a bad infestation, you might notice their fine silk webs, but the most common sign to see first is tiny holes that look like pale, mottled dots across leaves, usually white to pale yellow in colour, caused by their needle-like mouthparts piercing the leaf to feed.

Spider mites love warm, dry, sheltered conditions. Dusty leaves put out the welcome mat too, especially if the plant is also under water stress from low humidity or underwatering.

Although you’re unlikely to see spider mites without the help of a magnifying glass, there are telltale signs you can watch out for.

All plants can get these critters, but thinner-leafed plants are their favourites – one reason spider mites are so common on calathea.

Neem oil is often diluted and used as a leaf shine to keep dust at bay. I use Plant Runner’s neem oil about monthly. Neem also doubles as a natural pest repellent, although you’ll likely need stronger ammunition once infested.

For raising humidity, I use a small cordless H2O humidifier, but grouping plants together, and adding pebbles and water to a tray underneath also helps lift humidity a little.

When conditions are right, spider mites can go from egg to adult within a week. Females can lay some 20 eggs a day, which can hatch in as quickly as three days – one reason they seem to get so bad so fast, and also why changing treatments is recommended so they don’t become resistant.

Once they’ve set up home, my first go-to for treatment is insecticidal neem. You need the strong stuff. Some neem products are pre-diluted to be used as a leaf shine, which can help repel pests but often isn’t strong enough to treat them once infested. When I’m in battle mode, my go-to is BioNeem made by Grosafe. Dilute and spray leaves thoroughly, especially underneath leaves.

With spider mites, it’s best to repeat treat. Frequency depends on your treatment of choice but using a different product each time is recommended due to their short lifecycle. I have Yates Mavrik and Yates Bug Oil on-hand for repeat attacks.

That speedy lifecycle is also why following up your contact insecticide of choice with a systemic insecticide is the best bet to stop reinfestation. I reach for my trusty Groventive again for these guys. It feels a bit sad to say I have a favourite insecticide!

Fungus gnats

I hate fungus gnats. And I’m not one to use the word hate lightly. Luckily they are more annoying to us than harmful to our plants.

You always know when you have fungus gnats because if there’s one thing they love more than our plants, it’s our breath, as they’re attracted to carbon dioxide. If you have flying bugs all up in your face, about the size of a fruit fly but that look like tiny mosquitoes, you’ve probably got fungus gnats.

When I first got into the indoor plant hobby in a big way, I started off as an over-waterer. Fungus gnats quickly moved in, appreciative of the moist soil that my bad habit caused and maintained.

Fungus gnats are common outdoors, so watering indoor plants outside and leaving them to drain is one way you could be inviting the pest in. Storing potting mix outdoors, especially if it’s damp, is like setting up a fungus gnat motel.

These tiny midge-like pests love moist soil with decomposing organic matter. Using a soil-less potting mix that drains fast and retains a low moisture level helps put up a “no vacancy” sign in your plant’s pot.

Fungus gnats are common outdoors, so watering indoor plants outside and leaving them to drain is one way you could be inviting the pest in.

My go-to for soil-less potting mix is a New Zealand brand called Bio Leaf. However, it’s not the flying adults you need to worry about (although it’s the adults that may drive you mad). It’s the larvae stage that can harm plant’s roots if they get to high enough numbers.

Since they fly, it can be hard to pinpoint which plants are infested. A trick to pinpoint the source is raw potato. Cut a potato into slices and lay them flat, pushed down slightly into the top of each plant’s soil. Remove them after about four hours and look for tiny white to translucent larvae with brown heads chomping on the potato.

Now you know which plants to treat, there is a long list of treatments you could try, from cinnamon to apple cider vinegar. I tried all the home remedies first without much luck.

The first thing that helps is to not be like me, so water only when your plants really need it. Don’t be afraid of letting them dry out. Of course, that’s no good if the plant in question loves always-moist soil (read peace lilies). But where you can, don’t water unless really needed.

Once they’ve set up home, the secret to evicting fungus gnats is to attack two stages of the lifecycle at once. Otherwise, treatment tends to only reduce the population but never get rid of them entirely. I target adults and larvae at the same time. One adult can lay up to 200 eggs in their short life (they live for seven to 10 days), and the whole lifecycle from egg to larvae, pupae to adult can be as short as three to four weeks.

Fungus gnats don’t just look like mini-mosquitoes, their treatment shares some similarities too. I use a combination of sticky traps to kill the adults, and mosquito granules as biological control to kill the larvae. Another popular treatment is hydrogen peroxide.

I used to get those bright yellow plant sticky traps, easily found at most hardware stores and garden centres, and cut them up. Laying them flat, sticky side up, on the surface of my plants, ready to nab every gnat before it can lay more eggs. However, in my hunt for something more aesthetically pleasing, I’ve found more stealthy green sticky traps called uBloomd which don’t scream “I have pests” like the yellow ones do.

To target the larvae, I use BTI. In New Zealand, you’ll find it sold under the name EasyTrap Mozzie Bits or Mozzie Dunks. Using about four tablespoons of BTI granules per 4.5 litres of very warm water, I brew what hobbyists call mozzie tea. Scoop out the granules an hour later and water the soil of your plants with your brew once cool. The BTI will get to work killing the larvae for the next couple of days.

You will need to keep those sticky traps in place for a while. Every adult you trap significantly reduces the population. Every time you water, make a fresh brew

of mozzie tea as the granules only target the larvae, not the eggs. Continue both for at least two lifecycles (six to eight weeks), and you’ll finally be able to enjoy your own cups of tea in peace.

Aphids

You wouldn’t want to see my plant cupboard. Owning a plant store means my plants become my guinea pigs for trying out every new product. However, when it comes to pest control, I’m a fan of having multipurpose products on hand that treat more than one bad bug.

When it comes to aphids, my go-to is either DIY insecticidal soap or neem oil. What I use depends on what I find first without getting lost in the depths of my jumble of plant supplies (as much as I’d love to Marie Kondo my plant cupboard, it’s a mess in there).

One treatment I make is a mix of rubbing alcohol (the same treatment I use for mealybugs), with water and liquid soap. For that, I mix five parts water and two parts rubbing alcohol with a teaspoon of liquid soap. I use pure castile soap. Another treatment I use is Grosafe BioNeem, the strong stuff that also works on spider mites, not the diluted leaf spray, along with water and Enspray 99. (Enspray 99 can also be used by itself for mealybugs, scale and spider mites.)

I fill up a fine mister with my potion of choice, and go to town. I want good coverage of leaves and stems, especially underneath the leaves and concentrating on new growth. The same sticky traps I use for fungus gnats do a great job catching aphids too. Yes, adult aphids fly. Being so mobile is why they can spread so quickly.

Like mealybugs, aphids also produce sugary honeydew that ants love, and sooty mould is a sign of both mealybugs and aphids.

Being 2-4mm long, adults are easy to see, but the first signs to watch for are the skins of young aphids, called nymphs. Nymphs moult, shedding their skin four times before they reach adulthood. Nymphs looks like miniature adults but without wings. Their skin casts look like small white pests, and often get mistaken for mealybugs, but they don’t move.

Another use for rubbing alcohol is to dip in a cotton bud or wipe and simply touch that to the visible aphids for an instant kill. If the infestation is only light and you’re not squeamish like me, you can also squish them with your fingers. For my bigger, more robust indoor plants, I take them outdoors and blast them with the hose. Doing that means water alone can get rid of aphids.

Of all the pests I’ve battled, I found aphids the easiest to win the war against. Fungus gnats are the most common and do the least damage but get my vote for the most annoying. Mealybugs, scale and spider mites are like houseguests that don’t get the hint and leave, typically requiring repeat treatments. But it’s good to know that with just a handful of supplies, you can be prepared for these uninvited house guests.

Like mealybugs, aphids also produce sugary honeydew that ants love, and sooty mould is a sign of both mealybugs and aphids.