Cane Botrytis
Beginner
Scientific Name: Botrytis cinerea
Identification
- Most serious on red raspberries.
- Infections occur at the tip of older leaves and grow through the leaf to the cane.
- Dark brown lesions form at the leaf node and spread up and down the cane
- Lesions on canes often exhibit a banding pattern, tissue underneath is healthy green.
- In winter, the lesions turn white or gray.
- Small black fruiting structures that look like grains of rice are embedded in the overwintering lesion.
- Infected canes are more susceptible to winter injury.
- Infected buds on fruiting canes are usually small, slow to break growth in the spring, and often do not produce lateral shoots.
- Symptoms are most severe inside the canopy of a high density planting and towards the base of canes, where moisture accumulates.
Often Confused With
Spur Blight
Period of Activity
Botrytis spores and conidia are mainly spread by wind from infected tissue. Older senescing raspberry leaves are infected in mid and late summer. Lesions on canes appear in early July and expand rapidly in late summer.
Scouting Notes
Inspect overwintering canes for sclerotia. Observe new canes for dark brown lesions that spread on the lower and middle portion of the cane. Examine mature or senescing leaves on the inside of the canopy and look for pale brown v-shaped lesions.
Thresholds
None established.
Advanced
Scientific Name: Botrytis cinerea
Identification
Cane botrytis, is caused by the fungus Botrytis cinerea, the same pathogen that causes botrytis grey mould on fruit. It is most serious on certain varieties of red raspberries.
Brown lesions form on the lower cane at the leaf node, spreading up and down the cane to cover several internodes. Due to the irregular growth rate of the fungus, the lesions on canes develop a banding pattern, much like a watermark. Scraping the lesions reveals healthy green tissue underneath.
Once primocanes turn brown in the fall, the lesions become almost indistinguishable from healthy tissues. However, as temperatures continue to decline in the winter the lesions turn white or gray. Fruiting structures, or sclerotia, are formed on overwintering lesions beneath the epidermis. These look like small black grains of rice embedded in the lesion.
Infected canes are susceptible to winter injury. Infected buds on fruiting canes are usually small, slow to break growth in the spring, and often do not produce lateral shoots.
Often Confused With
Spur Blight
Both spur blight and cane botrytis can occur on the same cane. Spur blight lesions are V -shaped, and are darker brown than those produced by cane botrytis. Spur blight lesions are centered below a single node, while cane botrytis lesions extend along several internodes. Cane botrytis lesions exhibit zones of growth with a banding pattern much like a watermark.
Biology
The fungus overwinters mainly in sclerotia embedded in infected canes and sometimes as mycelium in infected plant parts. Between mid-March and the end of the growing season, sclerotia produce conidia whenever high humidity conditions exist. Conidia can also come from many sources of decaying plant debris. They are mainly wind-dispersed but can also be scattered by splashing rain. Their numbers usually peak in mid-summer and decrease thereafter. Plant parts must be wet for infection to occur.
The first infections of cane botrytis occur in mid or late summer. Infections occur at the tip of a leaf and grow through the leaf to the cane. Mature and senescing leaves are most susceptible, while young and immature leaves remain immune. Infected leaves develop pale brown v-shaped lesions that extend along the vein to the petiole, node, and cane of the plant. The disease is most common inside the canopy of a high density planting and towards the base of canes where moisture accumulates.
Infected leaves usually drop prematurely. In rare cases lesions on primocanes can affect an entire portion of the cane, causing girdling and death of the primocane.
Fruiting structures or sclerotia are formed on overwintering lesions beneath the epidermis. These look like small black grains of rice embedded in the lesion.
Period of Activity
Overwintering sclerotia produce grey masses of conidia in damp spring weather. Older senescing raspberry leaves are infected in mid and late summer. Cane lesions first occur in the beginning of July and expand rapidly in late summer between late July and August.
Scouting Notes
Inspect overwintering canes for sclerotia. Watch new canes for dark brown lesions that spread on the lower and middle portion of the cane. Examine mature or senescing leaves on the inside of the canopy and look for pale brown lesions that might have traveled down the leaf vein to the petiole and node.
Thresholds
None established.
Management Notes
- Keep rows narrow by mowing primocanes as they emerge at the row edges and control weeds to improve drying in the row.
- Prune out old fruiting canes and any diseased canes after harvest. Destroy any diseased canes.
- Space rows at least 2.5 m apart. Limit the width of plants within rows to 30-45 cm. Thin excess canes in the row.
- Avoid excessive use of nitrogen fertilizer.
- Early fungicides are important to reduce overwintering inoculum. Fungicides used for control of botrytis fruit rot may also help to suppress cane botrytis. Spray primocane growth during green fruit stage and post-harvest.
- Field observation suggests Nova and Titan are very susceptible to this disease. Polka shows a high tolerance to cane botrytis.
