Notes on Raspberry Diseases
Cane botrytis
Identification
Cane botrytis is often confused with spur blight. The two diseases frequently
occur together but cane botrytis is usually more serious. Infections begin
on old senescing leaves and travel down the leaf vein to the cane. Cane
lesions are dark brown, spread up and down and cover several internodes.
Lesions are lighter brown than spur blight lesions and may exhibit zones
or bands of growth. These cane lesions turn greyish white in the winter
months. Fruiting structures or sclerotia, are formed on overwintering
lesions. These look like small black grains of rice imbedded in the lesion.
Infected buds are more susceptible to winter injury and are slow to break
growth in the spring.
Cane botrytis symptoms on
raspberry primocane
Period of Activity
Overwintering sclerotia produce grey masses of conidia in damp spring
weather. However, botrytis inoculum can come from many sources of decaying
plant debris. Infections occur through older senescing raspberry leaves
in mid-late summer. Cane lesions expand rapidly in late summer.
Monitoring
Inspect overwintering canes for sclerotia. Watch new canes for dark lesions
that spread on the lower and middle portion of the cane.
Management notes
Keep rows narrow and control weeds to improve drying in the row. Early
fungicides are important to reduce overwintering inoculum. Fungicides
used for control of botrytis fruit rot may also help to suppress cane
botrytis. Field observation suggests Nova and Titan are very susceptible
to this disease.
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