Why Are My Argyranthemum Leaves Curling?

Aphid infestation

Aphids are the most frequent pest problem on argyranthemum. They particularly colonise the soft shoot tips and the undersides of young leaves, where their feeding causes the leaves to pucker, curl inward, and distort. Dense colonies can stunt new growth significantly and cause flower buds to abort before opening. Green peach aphid is the most common species, though blackfly and root aphids are also occasionally encountered on container-grown plants.

Argyranthemum in sheltered patio positions may develop aphid problems earlier in spring than plants in more exposed settings, as the warmth accelerates aphid reproduction before natural predators arrive.

What to do

• Pinch out and bin shoot tips bearing dense aphid colonies.
• Spray the whole plant with insecticidal soap, covering shoot tips and the undersides of young leaves thoroughly. Repeat every four to five days for two to three weeks.
• A jet of water dislodges aphids effectively from firmer parts of the plant before chemical control.
• Regular deadheading and inspection keeps populations in check before they build to damaging levels.

Leafminer

Leafminer is a very common and distinctive problem on argyranthemum. The adult fly lays its eggs inside the leaf, and the larvae tunnel through the tissue between the upper and lower leaf surfaces, leaving pale, squiggly serpentine trails visible through the leaf. The tunnelled areas dry out, turn papery, and the surrounding leaf tissue curls and dies back. Heavy infestations make the plant look unsightly and reduce vigour, though they rarely kill an otherwise healthy plant.

What to do

• Remove and bin heavily mined leaves promptly to reduce the leafminer population and prevent spread.
• On smaller infestations, the larvae inside individual trails can be squashed between finger and thumb.
• Yellow sticky traps near the plant catch adult leafminer flies and provide useful early warning of the pest's presence.
• Chemical controls are generally ineffective because the larvae are protected within the leaf tissue. Biological control with the parasitic wasp Dacnusa sibirica is effective in greenhouse or conservatory situations.

Spider mite

Spider mite is a significant pest on argyranthemum during hot, dry summer weather. The mites colonise the undersides of the finely divided leaves and feed on the sap, causing the leaf surfaces to develop fine bronze or silvery stippling. The affected leaves curl, look bleached, and eventually drop. Fine webbing appears between leaves and along the stems in heavier infestations. Container plants on exposed sunny patios are particularly prone in midsummer.

What to do

• Examine the undersides of curling leaves closely for the tiny reddish or yellowish mites and their webbing.
• Spray the plant thoroughly with a strong water jet, concentrating on the undersides of leaves.
• Follow up with insecticidal soap or neem oil spray every five to seven days for four to six weeks until the population is eliminated.
• Increase air humidity around the plant: spider mites thrive in hot, dry air and dislike moisture on the leaf surfaces.

Underwatering

Argyranthemum in containers needs consistent watering to perform well, particularly during the flowering season when the plant is expending considerable energy on flower production. When the compost dries out between waterings, the finely divided leaves wilt and curl rapidly, and flower buds may drop. Recovery is usually quick once watered, but repeated drought stress causes the plant to become progressively weaker and more susceptible to pest attack.

What to do

• Water container argyranthemum when the top 2 cm of compost feel dry to the touch, ensuring water drains freely from the base of the pot.
• In warm weather, check daily: argyranthemum in a small pot on a sunny patio can dry out quickly.
• Feed weekly with a high-potassium liquid feed from early summer to maintain vigour and prolific flowering.
• Deadhead spent flowers regularly to keep the plant in active growth and reduce the moisture demand from maturing seed heads.

Chrysanthemum white rust

Chrysanthemum white rust is a notifiable disease in the UK, meaning it must be reported to the relevant plant health authority if it is confirmed. It affects argyranthemum and other plants in the daisy family, causing pale yellow spots on the upper leaf surface and corresponding creamy white, slightly raised pustules on the underside. Affected leaves curl, wilt, and eventually die. The disease spreads rapidly in cool, humid conditions and can devastate a collection of susceptible plants.

What to do

• If you suspect white rust, compare your symptoms carefully with official resources: the pale pustules on the underside of the leaf are the key diagnostic feature.
• Do not move potentially infected plants to new locations, and do not compost affected material.
• Contact the UK Plant Health Authority (APHA) if you believe your plants are affected, as white rust is a controlled pest.
• Buy argyranthemum from reputable nurseries with healthy stock, and inspect new plants carefully before introducing them to your garden or collection.

Frequently asked questions

Why are my argyranthemum leaves curling?

Argyranthemum leaves curl most often because of aphid infestation or leafminer damage. Aphids cluster on shoot tips and cause the leaves to pucker and curl. Leafminers tunnel through the leaf tissue, leaving distinctive pale squiggly trails, and the surrounding areas curl and die off.

What are the white lines on my argyranthemum leaves?

White or pale squiggly trails on argyranthemum leaves are caused by leafminer larvae, which tunnel through the leaf tissue between the upper and lower surfaces. The affected areas curl and dry out. Remove heavily mined leaves and dispose of them; the plant usually grows on without lasting harm.

How do I keep argyranthemum flowering all summer?

Deadhead argyranthemum regularly and feed weekly with a high-potassium liquid feed from early summer onwards. If the plant becomes leggy and tired in midsummer, cut it back by one third to encourage a fresh flush of compact growth and flowers. Keep consistently watered in containers.

Why are argyranthemum leaves curling and turning bronze?

Bronze or silvery stippled leaves that curl are a classic sign of spider mite infestation. Check the undersides of the leaves for the tiny mites and their fine webbing. Spider mite thrives in hot, dry conditions and is common on container-grown argyranthemum on sunny patios in midsummer.