What's eating my french marigold?

French marigolds (Tagetes patula) are widely used as companion plants precisely because they deter many pests, but they are not pest-free. Spider mites are the worst threat in dry conditions. Slugs damage seedlings; aphids cluster on soft growth; and leafhoppers can transmit aster yellows disease, causing distorted yellow plants.

Pale, stippled leaves with fine webbing underneath; whole plant can bronze and collapse in hot dry weather Mist foliage regularly; apply neem oil or miticide; isolate affected plants and ensure adequate watering

Yellow mottling on leaves; may vector aster yellows phytoplasma causing stunted, distorted, yellowed growth Remove and destroy infected plants immediately (no cure for aster yellows); use row cover on young plants; control weeds that harbour leafhoppers

Holes in leaves and stems, especially at seedling stage; slime trails overnight Iron phosphate bait; copper tape around pots; hand-pick; water in morning not evening