Pyracantha scab is an infection of the blossoms, leaves and fruit of Pyracantha by the fungus Venturia inaequalis f. sp. pyracanthae, resulting in flower loss, leaf fall and disfiguring black lesions on the fruit. The fungus was formerly known as Spilocaea pyracanthae but recent work demonstrated that the scab fungi affecting apple and pyracantha belong to the same species. Venturia inaequalis includes subpopulations that can only infect specific plant genera; therefore, the form that affects apple does not affect pyracantha and vice-versa. However, the scab fungus that affects Pyracantha also attacks Eriobotrya (loquat) and Mespilus (medlar) to a lesser extent.

You will see scab from spring until autumn.

You may see the following symptoms:

• On leaves: Infection appears initially as dark spots on the leaf surface. Infected leaves soon fall and a severe attack can extensively defoliate the plant
• On flowers: Infected flowers shrivel and blacken, and do not form fruit
• On fruit: Disfigured, blackened areas and cracking of the surface
• On shoots: Young shoots may die back

The symptoms on shoots can be similar to those of fireblight, but fireblight infection on Pyracantha is more sudden and severe than scab.

The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.

Non-chemical control

• Hygiene is important for control, since the fungus survives winter on infected fallen leaves, infected fruits and pustules on infected stems. Rake up and burn fallen leaves, or consign them to the local council green waste collection. Cut back infected parts to remove mummified fruits and stem infections. Note that rigorous cutting back will reduce flowering the following year
• Choose resistant plants. The Saphyr® range and ‘Golden Charmer’, ‘Shawnee’ and ‘Teton’ are all claimed to show some resistance to pyracantha scab

Chemical control

The fungicides tebuconazole (Provanto Fungus Fighter Concentrate), tebuconazole with trifloxystrobin (Provanto Fungus Fighter Plus, Toprose Fungus Control & Protect), and triticonazole (Fungus Clear Ultra) are approved for the control of a number of other diseases on ornamental plants, and may give some control of pyracantha scab, although this is not claimed by the manufacturers.

The following products contain a combination of both insecticide and fungicide, enabling the control of both damaging invertebrates and disease: triticonazole containing acetamiprid (Roseclear Ultra, Roseclear Ultra Gun). When a proprietary product contains an insecticide as well as a fungicide it would be preferable to use an alternative product if invertebrate damage is not a problem on the plants treated.

Inclusion of a product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.

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Fungicides for gardeners (Adobe Acrobat pdf document outlining fungicides available to gardeners)

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Chemicals: using a sprayer
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Chemicals: storing and disposing safely

The cause of scab on Pyracantha is the fungus Venturia inaequalis f. sp. pyracanthae. The fungus overwinters on fallen leaves and probably also on shrivelled fruit remaining on the plant and in pustules on the stems, then releases spores to reinfect new growth in spring. The spores of Venturia inaequalis f.sp. pyracanthae are dispersed mainly in water and to a limited extent by wind, so the disease is more severe under wet conditions.