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Citrus scab

Raised corky pale orange to brown warts form on young leaves, twigs and fruits, and badly hit leaves crinkle and twist.

Elsinoe fawcettii Fungus Fact sheet
Citrus scab (Elsinoe fawcettii): raised, corky scabs on young fruit
Photo: Scot Nelson from USA, CC0, via Wikimedia Commons

Crops it strikes

Kalamansi Calamansi Citrus, dalandan or ponkan Suha Pomelo

What you see

Spots or streaksCurled or mottled leaves

When to act

Watch each new flush and the fruit set: scab only infects young tissue in wet weather. Protect when a flush pushes or petals fall during rainy weeks, above all in nurseries and on calamansi and pomelo with scab last season.

What to spray

Active ingredients only, never brands. The FRAC group tells how it works: switch to a different group next time, so the disease does not learn to survive it. Spray only when the damage is worth the cost, and only with products registered with the Fertilizer and Pesticide Authority for your crop. Follow the label. The Shopee and Lazada links only show who sells something with that active ingredient, not a recommendation of any seller or product.

Resistance: Scab fungi in heavily sprayed citrus groves abroad became resistant to group 1 (benomyl, thiophanate methyl). Use group 1 at most twice a season and rotate it with copper.

How to prevent it

  • Raise rootstocks and budwood away from scabby orchards, and protect nursery flushes. Scabby seedlings grow stunted and hard to bud.
  • Prune each year for an open canopy, cut out dead wood and remove scabby twigs.
  • Water at the base, not over the canopy, and avoid crowding trees.
  • Time fertilizer so flushes come in drier weeks where you can. Young flush in the rain is what scab needs.

Not sure it is this one?

Many diseases look alike. Send a photo to Anee, the smart farm technician in anee.io. She reads it with your crop, its age and the weather, and tells you what it most likely is and what to do first. In Tagalog or English.

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