Geranium pests and diseases: how to recognise them

At a glance

How to grow geranium · All pests and diseases

Pests

• Broad miteNew leaves are twisted, hardened and distorted, with bronzed undersides; the mites are too small to see without magnification.Photo: David Riley, University of Georgia, Bugwood.org, CC BY 3.0, Wikimedia Commons
• Scale insectsSmall round or oval bumps on stems and along leaf veins, mostly underneath, that do not move and look like shells or scabs.Photo: BARAKAT2011, CC BY-SA 3.0, Wikimedia Commons
• Two-spotted spider miteFine pale stippling or mottling on the upper leaf surface; leaves may turn bronze.Also called: red spider mitePhoto: Gilles San Martin from Namur, Belgium, CC BY-SA 2.0, Wikimedia Commons
• Vine weevilDull black, pear-shaped weevils about 9 mm long with dirty-yellow flecks, feeding at night; they cannot fly.Also called: black vine weevilPhoto: Opuntia, CC BY-SA 3.0, Wikimedia Commons
• WhiteflyClouds of tiny white-winged insects, about 1.5 mm long, fly up when the plant is disturbed.Photo: gaucho, CC BY-SA 3.0, Wikimedia Commons

Diseases

• Grey mouldFuzzy grey-brown mould on decaying buds, flowers, leaves, stems or fruit in humid weather.Photo: Schlaghecken Josef, CC BY 4.0, Wikimedia Commons
• RustPale spots on the upper leaf surface, with raised powdery pustules mostly underneath; on beans they often have a yellow halo.Photo: Rasbak, CC BY-SA 3.0, Wikimedia Commons

Which geranium 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, almost translucent spots that turn brown and water-soaked; affected tissue goes soft, dark and dies, and buds and flowers shrivel.

Plants with many of the same problems

• Tuberous Begonia (5)
• Chrysanthemum (5)
• Cyclamen (5)
• Gloxinia (5)
• Grape (5)
• Green Beans (5)
• Primrose (5)
• African violet (4)

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. plants.ces.ncsu.edu/plants/pelargonium-hortorum/
4. rhs.org.uk/plants/pelargonium/growing-guide
5. rhs.org.uk/plants/geranium/growing-guide
6. rhs.org.uk/biodiversity/glasshouse-whitefly
7. ipm.ucanr.edu/agriculture/strawberry/whiteflies/
8. rhs.org.uk/disease/grey-mould
9. ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/botrytis.html
10. plants.ces.ncsu.edu/plants/geranium-sanguineum/