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Raspberry Cane Blight



P_raspcnblt

Raspberry Cane Blight

Usually appear in

Spring to Autumn.


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Caused By:-     The Fungus Leptosphaeria coniothyrium

Description

Raspberry Cane Blight is caused by the fungus Leptosphaeria coniothyrium which survives in the soil and enters the base of canes through splits in the bark, often the result of cane-midge attacks.
Dark patches appear on the canes, in May or June, just above soil level which cracks, becomes cankerous and then covered in black spores. These spores can be wind blown to infect other plants or carried by water splashes. The canes may become brittle and may snap off easily. If the infected bark is scraped back it will show as an orange-red tissue.
The first symptom you are likely to see is the shrivelling and dying of leaves on the older, fruiting canes, but often there is a sudden wilting of cane or foliage. Often only a single branch wilts and the remainder of the plant is normal.
The fungus may cause damage in dry seasons, because it infects the Raspberry during the first season, but do not show effects until the following year.
Blackberries can also be affected, but on them the disease is minor. The fungus causing cane blight can also cause a canker disease of roses and a root rot of strawberries.
Picture by Florida Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org.


Control

Once spotted cut out and burn any affected canes. Cut back to below soil level and disinfect the secateurs between cuts.
The spores survive for several years in the soil on old raspberry materials, so plant new raspberries somewhere else. Do not plant strawberries in infected ground either as this fungus will attack their roots.
Spraying with a copper-based fungicide may help prevent Raspberry Cane Blight and also other diseases diseases, but you need to start spraying in March when the buds are about 1cm long and repeat as recommended.
Avoid unnecessary damage to the canes especially near the soil.
Poor soils and conditions especially waterlogging, weaken the plants and make them more susceptible to attack. Therefore mulch plants during the winter dormant period.
Ensure that they are well spaced so that air circulates and the canes dry out quickly after rain or heavy dew.
Raspberries will pick up diseases and viruses over the years which gradually reduce their productivity. Therefore it might be sensible to replace the plants with new stock every five to seven years.
Some varieties of raspberries show resistance to this disease.



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