Botrytis cinerea, the fungus that causes grey mould disease, is the most important pathogen in Rubus cane fruits worldwide. It accounts for severe yield losses in most seasons and can cause devastating losses post-harvest if control measures are inadequate, especially in regions with moderate rainfall during blossom and harvest. This pathogen is difficult to control because there are multiple infection sites and no strongly resistant cultivars are available to growers. It infects newly opened flowers and mature leaves, and survives winter as sclerotia and mycelium in external tissues of fruiting canes and in dead crop debris to produce abundant inoculum for infection of flowers in the following year. Ripe fruits are susceptible to disease spread from mycelium on attached infected petals, stamens and styles. Damage to drupelets caused by larvae of raspberry beetle also increase the extent of post-harvest grey mould.
There are several effective fungicides available, but raspberries and other Rubus cane fruits require spraying from first flower until shortly before fruit ripening to control post-harvest grey mould. However, many flowers are missed by a 7 to 10-day spray programme and therefore are left unprotected.
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| Grey mould on fruit |
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