Marigold pests and diseases: how to recognise them

At a glance

How to grow marigold · All pests and diseases

Pests

• Broad miteGrowing tips and buds are killed and new growth is stunted — easily mistaken for disease or herbicide damage.Photo: David Riley, University of Georgia, Bugwood.org, CC BY 3.0, Wikimedia Commons
• Leaf MinerHeavily mined leaves dry up or drop early; badly affected tomato plants can lose most of their leaves.Photo: Flowersabc, CC BY-SA 2.0, Wikimedia Commons
• Two-spotted spider miteFine silk webbing over leaves and shoot tips in heavy attacks.Also called: red spider mitePhoto: Gilles San Martin from Namur, Belgium, CC BY-SA 2.0, Wikimedia Commons
• WhiteflySticky honeydew on leaves, stems and fruit, followed by black sooty mould.Photo: gaucho, CC BY-SA 3.0, Wikimedia Commons

Diseases

• Grey mouldOn strawberries, grapes and other soft fruit a soft brown rot, often as the fruit ripens; on gooseberries whole branches die.Photo: Schlaghecken Josef, CC BY 4.0, Wikimedia Commons
• Tomato spotted wilt virusFruit with pale yellow or light green rings, often raised in the centre; ripe tomatoes blotched red and yellow; peppers with ring spots.Photo: Downtowngal, CC0, Wikimedia Commons
• White mould (Sclerotinia)Later, hard black seed-like bodies (sclerotia) 0.5–1 cm across in the mould and inside hollow stems.Photo: Schlaghecken Josef, CC BY-SA 4.0, Wikimedia Commons
• Verticillium wiltLower, older leaves yellow first — at the margins and between the main veins — then turn brown and wither; the damage moves up the plant.Photo: Howard F. Schwartz, Colorado State University, Bugwood.org, CC BY 3.0 us, Wikimedia Commons

Which marigold problems need quick action?

These spread or do lasting harm fast; check the plants and start treatment the day you see them.

• Grey mould: Small black seed-like bodies may form on the infected material.
• Tomato spotted wilt virus: Plants infected young often fail to flower or set fruit. There is no cure once a plant is infected.
• White mould (Sclerotinia): Roots, heads, pods and fruit can rot too, also in storage.

Plants with many of the same problems

• Chrysanthemum (8)
• Tomato (8)
• Chili Pepper (7)
• Cucumber (7)
• Eggplant (6)
• Green Beans (6)
• Tuberous Begonia (5)
• Dahlia (5)

Which plants each problem affects: sources

The links between these problems and the plant were checked against these pages.

1. ipm.cahnr.uconn.edu/ipm-managing-broad-mites-on-greenhouse-crops
2. extension.msstate.edu/newsletters/bugs-eye-view/2016/broad-mites-vol-2-no-16
3. gd.eppo.int/taxon/LIRIHU/hosts
4. gd.eppo.int/taxon/LIRITR/hosts
5. hgic.clemson.edu/factsheet/marigold/
6. rhs.org.uk/disease/grey-mould
7. ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/botrytis.html
8. pnwhandbooks.org/plantdisease/pathogen-articles/common/fungi/plants-susceptible-sclerotini
9. plantpathology.mgcafe.uky.edu/files/ppfs-vg-29.pdf
10. rhs.org.uk/disease/verticillium-wilt
11. ipm.ucanr.edu/PMG/GARDEN/FLOWERS/DISEASE/verticilliumwilt.html