Grow guide

Clivia pests, diseases and problems

Clivias are tough, but a few pests and problems turn up again and again. Here’s how to recognise them, what causes them and how to fix them, starting with the simplest options.

Key points

Most problems start with too much water, too little airflow or too much sun.
Check leaf bases regularly: mealybug and lily caterpillars hide where the leaves meet.
Lily caterpillars can destroy a clump quickly in warm, humid weather.
A soft, smelly base means rot: isolate the plant and act fast.
If you use a chemical, choose one registered for that pest and follow the label.

What's wrong with my clivia?

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Prevention first

Healthy clivias shrug off most problems, and nearly every serious one comes back to too much water, too little airflow or too much sun.

Use a coarse, free-draining mix and keep pots raised off the ground.
Space plants so air moves freely. At Valewood we treat good airflow as essential, because poor airflow leads to mealybug and leaf spots.
Water in the morning, at the base of the plant.
Remove old, yellowing leaves and debris, and isolate any sick plant.

Using sprays safely

Start with cultural controls: hand removal, better growing conditions and cutting off badly damaged growth. If you need a chemical, choose a product registered by the APVMA for that pest on ornamentals, and follow the label exactly, including the safety directions. Rotating products with different active ingredients helps stop mealybug becoming resistant.

Mealybug

Mealybugs are small, soft, oval insects coated in white, powdery wax. They hide where leaves meet and deep in the centre of the plant, sucking sap and leaving sticky honeydew that grows black sooty mould. Ants farm them for honeydew and protect them from predators, so control ants too.

Wipe off small numbers with a cotton bud dipped in methylated spirits. For bigger outbreaks, use a registered product such as a botanical or horticultural oil, a pyrethrum-based spray, or a systemic insecticide for heavy infestations, applied while the plant is actively growing. Repeat as the label directs, because new young mealybugs keep hatching.

Root mealybug

Some mealybugs live on the roots and are often only found at repotting, as white, cottony patches on the roots and inside the pot. Suspect them if a plant stalls or yellows despite good care. Wash off the old mix, trim badly affected roots, repot into fresh mix and a clean pot, and bin the old mix.

Scale

Scale insects are small, flat or domed brown or white bumps on the leaves and leaf bases. They suck sap and produce honeydew. Scrape off light infestations with a soft brush, and use a horticultural or botanical oil registered for scale on heavier ones.

Caterpillars work fast

Lily caterpillars can devour a plant almost overnight. In warm, humid weather, check the leaf bases at least weekly.

Lily caterpillar and lily borer

The lily caterpillar (Spodoptera picta) is the caterpillar most often reported on clivias in Australia. It grows to about 5 cm and is striped black, grey and yellow with black spots. The caterpillars feed at night, often in groups, chewing the leaves and then boring into the leaf bases and crown, and can kill the plant. They’re most active in hot, wet, humid weather.

The lily borer (Brithys crini), black with white spots and an orange head, also occurs in Queensland, NSW and the Northern Territory. Australian records list it mostly on crinums and other amaryllis-family plants, but treat it the same way if you find it.

Check plants from late spring to autumn, ideally at dawn or after dark. Look for chewed leaves and droppings in the leaf bases. Pick off and squash caterpillars, and bin badly damaged leaves. For larger numbers, use an insecticide registered for caterpillars on ornamentals, such as a Bacillus thuringiensis (Bt) spray or a spinosad or spinetoram product.

Snails and slugs

Snails and slugs chew leaves, new growth, buds and flowers, mostly on damp nights. Hand-pick them after rain, use beer traps, or surround plants with a gritty barrier. Any snail bait can poison a dog or cat that eats enough, including products sold as safer, so use as little as the label allows and keep it where pets can’t reach.

Fungus gnats

These tiny, dark flies hover around damp pots and seedlings, and their larvae feed on young roots. Let the surface of the mix dry between waterings, avoid fresh compost in pots, and trap adults with yellow sticky cards. Beneficial nematodes are a biological option for the larvae.

Our first line of defence

Good airflow and careful watering prevent most problems. Our plants sit on waist-height benches, and we never water in the evening, when rain is forecast or when it’s over 30°C.

Root and crown rot

Rot is one of the biggest threats to clivias, and it almost always starts with a wet, poorly drained mix. Signs include yellowing lower leaves, a plant that wilts or wobbles even though the mix is wet, and brown, mushy roots. Unpot the plant, cut away all rotten tissue with a clean blade, let it dry for a day, and repot into fresh, coarse mix. Water sparingly until new roots form. A fungicide registered for root rot in ornamentals, such as a phosphorous acid or copper product, can help.

Bacterial soft rot

Soft rot is easy to miss until it’s advanced. It often starts with one or two yellowing lower leaves and may not be noticed until the plant falls over. The base becomes dark, sodden and foul-smelling. It spreads easily, so isolate the plant immediately.

If caught early, cut away all soft tissue back to firm, healthy tissue, wiping your blade with methylated spirits after every cut. Treat the cut with a product registered for the purpose, let it dry for a day or so, then repot in fresh, coarse mix and keep it on the dry side. Warm, wet conditions favour soft rot, which is why at Valewood we don’t water when it’s over 30°C.

Leaf spots and rust-coloured marks

Brown, tan or reddish spots, sometimes with yellow halos or rings, are usually fungal, including anthracnose (Colletotrichum). Growers often call these marks rust. Wet leaves and still, humid air encourage them. Remove badly marked leaves, improve airflow and water at the base in the morning. If spots keep spreading, use a fungicide registered for leaf spot on ornamentals, such as a copper or mancozeb product. Rule out sunburn, frost and mealybug damage first.

Take a torch

Snails, slugs and lily caterpillars feed at night. A quick look with a torch after dark often finds what a daytime search misses.

Sunburn and frost damage

Sunburn shows as bleached, yellow or white patches on leaves facing the sun, which later turn brown and papery. Move the plant into more shade. Burnt leaves won’t recover, but new ones will be fine.

Frost damage shows as water-soaked patches that later collapse and turn brown. Protect plants under trees, eaves or frost cloth, and trim damaged leaves once the frost season has passed.

Yellowing leaves

Old outer leaves yellow and die off naturally. Just remove them.
Too much sun bleaches leaves, especially when the plant is also dry.
Too much water leads to root rot and yellowing.
Soft rot often starts with yellow lower leaves, so check the base.
Root mealybug causes yellowing that doesn’t respond to better care.
Nutrient problems from an exhausted mix, or one that’s too alkaline or acidic. Feed, or repot into fresh mix.

Brown leaf tips

Brown tips usually point to water stress or salt build-up: the mix drying out too far between waterings, or too much fertiliser. Feed at label rates, and now and then water thoroughly on a mild morning so clean water flushes through the pot. Cold and sun can also brown the tips.

Short or stuck flower stems

Sometimes a flower head opens down among the leaves instead of on a tall stem, which some growers call bird nesting. Sources disagree on the cause, but the usual suspects are a winter too warm to give enough chill, a cold snap or dry spell while the stem is lengthening, and genetics. Give plants a cool (not frosty) winter rest, and once a bud appears, water a little more on mild mornings.

If your clivia won’t flower at all, see why won’t my clivia flower?

Common questions

What's the white fluffy stuff between the leaves?

Almost certainly mealybug. Wipe off small numbers with methylated spirits on a cotton bud, and control ants.

Can a clivia with a soft, smelly base be saved?

Sometimes, if you act fast. Isolate it and follow the steps under bacterial soft rot above.

Sources and further reading (24)

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Clivia pests, diseases and problems

What's wrong with my clivia?

Prevention first

Using sprays safely

Mealybug

Root mealybug

Scale

Lily caterpillar and lily borer

Snails and slugs

Fungus gnats

Root and crown rot

Bacterial soft rot

Leaf spots and rust-coloured marks

Sunburn and frost damage

Yellowing leaves

Brown leaf tips

Short or stuck flower stems

Common questions

Keep learning

Clivias 101

Care calendar

Why won't it flower?

Colours and breeding

Potting and dividing

Raising from seed

Questions, answered

Clivia glossary

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