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Poinsettia pests and diseases

Poinsettia – Euphorbia pulcherrima 'Snowcap White'
Photo: Jardin botanique de Montréal (Gilles Murray)
Euphorbia pulcherrima

Poinsettias can fall victim to diseases and pests. Here are some top tips to fend off fungal infections and control whiteflies, the plant’s number-one pest.

Pathogenic fungi

Poinsettias can be affected by stem, crown, and root rot, caused by fungi such as Pythium sp., Rhizoctonia sp., Thielaviopsis sp., and Phytophthora sp. Excessive watering or poor soil drainage fosters the development of these fungi. Use a well-drained substrate and allow the soil surface to dry between waterings.

Whiteflies—the primary insect pest of poinsettias

Whiteflies are the most common insect pest of poinsettias. Inspect foliage regularly, especially the underside of leaves, for clusters of eggs and larvae. Here’s how to control whiteflies:

  • Prune and dispose of heavily infested parts.
  • Use yellow sticky traps to catch adult whiteflies.
  • Capture them with a handheld vacuum.
  • As a last resort, use a low-impact pesticide.

 Other pests like mealybugs, spider mites, and thrips can also damage poinsettias but are less common.

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