Pest identification
What's eating my sulphur cosmos?
Aphids
Signs: Soft yellow-green or black colonies on growing tips and flower buds; distorted new leaves and sticky honeydew deposits.
Control: Dislodge with a water jet; apply insecticidal soap or neem oil; the plant's own pollinator traffic often brings aphid predators.
Spider mites (Tetranychus urticae)
Signs: Fine pale stippling on upper leaf surfaces; dusty webbing on leaf undersides; plants look bleached and may defoliate in severe heat.
Control: Increase humidity and water adequately during drought; apply neem oil or insecticidal soap; introduce Phytoseiulus predatory mites in greenhouses.
Slugs & snails
Signs: Seedlings and transplants cut off at soil level; ragged holes in lower foliage with visible mucus trails.
Control: Start seeds indoors and transplant well-grown plants; scatter iron phosphate pellets; use grit mulch around stems.
Keep sulphur cosmos pest-free
Healthy plants resist pests best. Get the basics right:
Sulphur Cosmos pests — FAQ
What is eating my sulphur cosmos?
Sulphur Cosmos is a robust, heat-loving annual with good pest resistance, but aphids colonise the shoot tips and spider mites can be a problem in hot dry spells. Slugs damage seedlings. The bright yellow-orange flowers attract beneficial insects that naturally suppress many pests, making it one of the easier annuals to grow without intervention.
How do I get rid of aphids on sulphur cosmos?
Soft yellow-green or black colonies on growing tips and flower buds; distorted new leaves and sticky honeydew deposits. Dislodge with a water jet; apply insecticidal soap or neem oil; the plant's own pollinator traffic often brings aphid predators.
How do I get rid of spider mites (tetranychus urticae) on sulphur cosmos?
Fine pale stippling on upper leaf surfaces; dusty webbing on leaf undersides; plants look bleached and may defoliate in severe heat. Increase humidity and water adequately during drought; apply neem oil or insecticidal soap; introduce Phytoseiulus predatory mites in greenhouses.
How do I get rid of slugs & snails on sulphur cosmos?
Seedlings and transplants cut off at soil level; ragged holes in lower foliage with visible mucus trails. Start seeds indoors and transplant well-grown plants; scatter iron phosphate pellets; use grit mulch around stems.