Last round of the plant problems series!

Not because we’ve magically covered every possible thing that can go wrong with a houseplant (we absolutely haven’t), but because this is where we wrap up the “big three”: light, water, temperature… and now pests and diseases.

If you only take one thing away from this post, let it be this:

Healthy plants get fewer problems.

A well-fed, well-potted, appropriately watered plant in decent light is much less likely to be hammered by pests or knocked over by disease. It’s not bulletproof, but it is better equipped to bounce back when something does have a nibble or a nibble-adjacent fungal situation.

So the goal here isn’t just “how do I kill the thing that’s eating my monstera” – it’s also “how do I set this plant up so I’m not fighting a new outbreak every second Tuesday”.

We’ll break it into:

• Prevention (your best friend)
• Common indoor pests (and what to do, step by step)
• Common indoor diseases (and how to stop them spreading)
• When to call it, compost it, or start again

First: Prevention > Cure 

Before we go bug-by-bug, a quick checklist. If you tighten these up, you’ll instantly reduce how often you’re dealing with pest dramas:

1. Quarantine new plants

That gorgeous new Ficus lyrata (fiddle leaf fig) you brought home? Park it away from the rest of the collection for 2–3 weeks. Use this time to:

• Check the undersides of leaves
• Watch new growth for distortion or stickiness
• Keep an eye out for webbing, tiny spots or fluff

Future you will be very, very grateful.

2. Clean leaves regularly

Dusty, grimy leaves = reduced photosynthesis and a comfy hiding spot for sap suckers.

• Wipe leaves gently with a damp cloth
• Use a leaf-cleaning product or leaf shine to remove residue and help you spot pests early
• Avoid harsh midday sun straight after any oil-based sprays or leaf products

Clean foliage isn’t just about pretty photos – it helps you see problems early.

3. Don’t overwater, don’t underwater

Soggy mix and stressed roots = stressed plant. Stressed plant = pest magnet.

Let the top of the mix dry to the right level for that species, and make sure your potting mix is free-draining and appropriate for the plant (hello, chunky mixes for aroids and free-draining blends for succulents).

4. Airflow matters

Crowded plants in a still, humid corner? Perfect environment for fungal spots and mites. Give them:

• A bit of space between pots
• Occasional gentle air movement (open windows when weather allows, avoid freezing draughts or aircon blasting directly on leaves)

Right. Now that the “eat your veggies” lecture is done, let’s talk pests.

Pests: Who’s Eating What, and What You Can Do

Most indoor pests are sap suckers. They pierce the leaf or stem and drink the plant’s juices like a tiny vampire smoothie. The good news? The management steps are very similar across species.

We’ll cover:

• Aphids
• Mealybug
• Scale
• Spider mite

And we’ll give you a simple action plan for each.

Aphids

What they look like:
Tiny, soft-bodied insects – usually green, black or brown – that love the tender new growth. You’ll often find them clustered on new shoots, buds, and the undersides of young leaves.

What they do:

• Curl and distort new growth
• Leave behind sticky “honeydew” that can attract sooty mould
• Slow overall growth if left unchecked

What to do:

1. Isolate the plant
   Move it away from your other plants – aphids are happily mobile with a bit of help from air currents and you.

2. Hose / shower them off
   If the plant can handle it (think hardy aroids, not fragile ferns):

   • Take it outside or into the shower
   • Use a firm but gentle spray to wash as many aphids off as possible
   • Let it drain thoroughly before putting it back in its cover pot

3. Follow up with a mild soap solution
   

   • Mix a tiny amount of gentle liquid soap in water
   • Wipe down affected areas (both sides of the leaves and stems) with a soft cloth or sponge
   • Avoid soaking the soil – we’re cleaning the foliage, not making bubble tea

    

4. Repeat weekly until clear
   Aphids breed fast. Check new growth regularly and repeat the wipe-down if needed.

Mealybug

What they look like:
Little white, cottony tufts tucked into leaf joints, stems, veins and the nooks and crannies of your plant. Once you see them, you can’t unsee them.

What they do:

• Suck sap, leading to yellowing, weak foliage
• Excrete sticky honeydew that can lead to sooty mould
• Hide in crevices – they love bases of leaves and nodes

What to do:

1. Isolate the plant
   Mealybug can easily hitchhike on your hands or tools.

2. Mechanical removal (very satisfying)
   

   • Use a damp cloth, cotton pad or cotton bud to wipe/squish each clump
   • Pay attention to leaf joints, stems and under leaves
   • Take your time – this is more “slow Sunday job” than “rushed before work”

    

3. Spot treat stubborn clusters
   Many growers use a cotton bud dipped in a mild soap solution to dab at particularly stubborn patches, then wipe away.

4. Clean the foliage
   Once the obvious bugs are gone:

   • Wipe the whole plant down again with fresh water or a leaf-cleaning product
   • This helps remove honeydew and reduce the risk of sooty mould

5. Inspect weekly for 3–4 weeks
   Mealybugs are experts at hiding. Keep checking the plant (and nearby ones) to catch any stragglers early.

Scale

What they look like:
Little bumps on stems, petioles and leaves – often brown, black or tan. They look a bit like the plant has grown its own barnacles.

What they do:

• Suck sap, slowly weakening the plant
• Cause yellowing leaves and general decline
• Also produce honeydew → sooty mould

What to do:

1. Isolate the plant
   Again, prevention of spread is key.

2. Scrape and wipe
   

   • Use a fingernail, old loyalty card, or cloth to gently scrape scale off the stems and leaves
   • Be gentle – you’re trying not to damage the plant tissue underneath
   • Wipe the area clean afterwards

    

3. Deep clean
   

   • Wipe the entire plant down with water and a dash of mild soap
   • Rinse or wipe again with plain water so there’s no residue left

    

4. Repeat
   Scale insects are stubborn. You’ll often need a few rounds of scraping and wiping over a couple of weeks.

5. Check nearby plants
   If one plant has scale, anything that’s been touching it or sitting right next to it is worth checking closely too.

Spider Mite

You do not want these getting established.

What they look like:

• Tiny red, brown or pale specks – often hard to see with the naked eye
• Fine, almost cobweb-like webbing between leaves, stems and nodes
• Leaves that look stippled, speckled or washed out

They love warm, dry, still air and will party hard on your Calatheas, Ficus, and many aroids if you let them.

What to do:

1. Immediate quarantine
   Get the plant away from everything else the second you suspect mites.

2. Rinse thoroughly
   

   • Take the plant to the shower or outside
   • Rinse leaves (top and bottom) and stems carefully
   • Let it drain fully

    

3. Clean with mild soap solution
   

   • Wipe each leaf (both sides) with a soft cloth dipped in a gentle soapy water mix
   • Focus on the undersides where mites hang out

    

4. Increase humidity and airflow (but avoid cold drafts)
   Spider mites hate consistent moisture on foliage and improved humidity. Just don’t go so far that you create a fungal party instead.

5. Repeat every 5–7 days
   

   • Clean again weekly for at least 3–4 cycles
   • Keep the plant quarantined until you’ve had a couple of weeks with no new webbing, speckling or damage

    

If a plant is absolutely covered and you have a whole collection at risk, sometimes the best move for your overall “plant fam” is to say goodbye to that one heavily infested plant and protect the rest.

Diseases: When Things Get Spotty, Sticky or Mushy

Indoor plant diseases are usually opportunists. They love:

• Constantly wet foliage
• Soggy potting mix
• Poor airflow
• Untreated pest problems (hello, honeydew)

The big ones you’ll see with houseplants:

• Sooty mould
• Leaf spot
• Crown/root rot
• Bacterial blight

Sooty Mould

What it looks like:
Black, sooty-looking film or patches on leaves and stems. It feels a bit sticky or grimy and often appears on plants that also have aphids, scale or mealybug.

What’s actually going on:
Sooty mould isn’t attacking the plant directly – it’s feeding on honeydew, the sugary excrement from sap-sucking pests. But it does block light, which reduces photosynthesis and generally makes your plant look very sad.

What to do:

1. Deal with the pest problem first
   If you don’t remove the aphids/scale/mealybug, the mould will just keep coming back.

2. Clean the foliage
   

   • Gently wipe leaves with a damp cloth
   • For thicker deposits, you may need to go over them a couple of times
   • A leaf-cleaning product or leaf shine can help remove residue and get leaves back to actually looking green again

    

3. Improve airflow and light
   Once clean and pest-free, give the plant decent light and space so leaves dry more readily after watering.

Leaf Spot

“Leaf spot” is a bit of an umbrella term – spots can be caused by fungal or bacterial pathogens, and from the outside they can look pretty similar.

What it looks like:

• Yellow, brown or dark spots on the leaf surface
• Sometimes with a halo or ring around the spot
• In bad cases, spots can merge and sections of the leaf die off

What to do:

1. Remove affected leaves
   

   • Use clean, sharp scissors or secateurs
   • Bin the leaves (don’t compost disease-heavy material if you can avoid it)

    

2. Change how you water
   

   • Water the soil, not over the top of the plant
   • Avoid constant leaf wetness, especially at night
   • Don’t mist a plant that’s already dealing with leaf spots

    

3. Improve spacing and airflow
   Move plants slightly apart so leaves aren’t always touching. More air movement means leaves dry faster and spores are less likely to take hold.

4. Monitor new growth
   If new leaves grow in clean and the spread stops, you’re winning. If the problem is severe or persistent, talk to your local nursery about suitable fungicide options for home use and always follow the label directions.

Crown Rot / Root Rot

The classic “I over-loved it with water” disease.

What it looks like above the soil:

• Yellowing or wilting leaves despite the soil being wet
• Mushy stems near the base
• Plant that collapses without an obvious pest

What it looks like below the soil:

• Black, brown, mushy roots that slough off in your fingers
• Bad smell from the potting mix

What to do (emergency surgery):

1. Get the plant out of the pot
   Gently ease it out and take a good look at the roots.

2. Trim off all rotten roots
   

   • Use clean scissors
   • Remove anything mushy, black or foul-smelling
   • Keep only firm, pale, healthy roots

    

3. Repot into fresh, free-draining mix
   

   • Choose a pot with drainage holes (non-negotiable)
   • Use an appropriate mix – chunky aroid blend for things like Monstera deliciosa, Philodendron, Epipremnum; lighter free-draining indoor blend for others
   • Avoid reusing the old, infected mix

    

4. Water carefully
   

   • Water once after repotting to settle the mix
   • Then let the top portion of the soil dry out properly before watering again
   • Think “slightly damp sponge” rather than “swamp”

    

5. Adjust care going forward
   Often root rot is a symptom of:

   • Too much water
   • Not enough light
   • A mix that holds too much moisture

   Fix those, and you dramatically reduce the chances of a repeat performance.

Bacterial Blight

What it looks like:

• Pale green, water-soaked spots that can blister
• Spots may turn brown or black over time
• Leaves may wilt, especially in humid or poor airflow conditions

What to do:

1. Prune out infected foliage
   

   • Sterilise your tools before and after (methylated spirits, boiling water, etc.)
   • Remove all visibly affected leaves and any that are starting to show similar lesions

    

2. Stop misting
   Water on leaves spreads bacteria around. Water the soil only, and try to keep foliage dry.

3. Improve airflow
   Give the plant space and air – crowded, still, humid corners are not your friend here.

4. Don’t leave dead foliage sitting on the soil
   Remove fallen leaves and debris regularly so you’re not giving pathogens a comfy home base.

5. Monitor and be realistic
   Mild infections can often be brought under control with hygiene and environmental tweaks. If an entire plant is collapsing and everything is infected, sometimes starting fresh with a clean cutting or new plant is less stressful in the long run.

When to Fight, When to Walk Away

Not every plant can (or should) be saved. A few thoughts to keep your sanity intact:

• Fight for: sentimental plants, rare or expensive plants, and anything where the problem is caught early and localised.
• Be ruthless with: heavily infested budget plants, or anything that’s risking your entire collection. If one $15 plant is endangering ten established favourites, you know what to do.
• Always learn from it: was it too dark? Too wet? Poor mix? No quarantine? Use each problem as a mini case study so you can avoid the same mistake with the next plant.

Remember: everyone who grows indoor plants has had pests, root rot, mysterious spots… the lot. It’s not a sign you’re bad at this; it’s just part of the hobby. The trick is learning to spot issues early, responding calmly, and setting your plants up so problems are the exception, not the rule.

Quick Cheat Sheet

• Sticky leaves + black sooty film → Check for aphids, scale, mealybug. Clean leaves, treat pests, improve airflow.
• Fine webbing + speckled leaves → Spider mites. Quarantine, rinse, clean regularly, increase humidity.
• Yellowing leaves + soggy mix + black roots → Root rot. Trim roots, repot into free-draining mix, adjust watering.
• Spots on leaves + constant misting → Leaf spot. Prune, keep foliage dry, improve airflow.

Dial in the basics, keep an eye on your plants, and you’ll spend a lot more time enjoying fresh growth than fighting tiny insects.