What's eating my marigold?

Marigolds (Tagetes) are famously pest-repellent companions but are themselves attacked by spider mites in hot dry summers, slugs on young plants, aphids, and in the US by leafhoppers that transmit aster yellows. Marigolds are generally very hardy, but spider mites are the most reliable pest threat, particularly for French marigolds in hot, dry conditions.

Fine pale stippling on leaves, yellowish-bronze discolouration, and delicate webbing between leaves and stems; plants look dull and dusty in hot, dry spells and can defoliate in severe infestations. Water plants during dry spells to maintain healthy growth; spray with water to dislodge mites; apply neem oil or insecticidal soap to both leaf surfaces; space plants for good air flow.

Young transplants and seedlings are eaten overnight, with irregular holes in leaves and silvery slime trails visible in the morning. Protect transplants with iron phosphate pellets; use slug barriers on raised beds; grow larger transplants before planting out rather than small, vulnerable seedlings.

Green or black colonies on shoot tips and buds, distorting new growth; generally less severe on marigolds than on many other flowers but can build up on softer-stemmed cultivars. Blast off with water; allow natural predators to build up; apply insecticidal soap if colonies are large; plant near other flowers to attract hoverflies and ladybirds.