Soft, brown, rapidly spreading, wet rot with white, cottony, dense fungal growth on the surface of heads and stems. It sometimes has black, hard spore bodies (sclerotia) which may be formed inside the stems or on the surface.
Sclerotia of Sclerotinia sclerotiorum are 5-10 mm long, irregular shape and look like rat faeces.
Symptoms vary between species.
In Beans the infected pods look normal at harvest and develop the rot in storage.
In Canola a white fluffy growth appears on the stem which is greyish white or brownish white underneath the fluff or later in the season. Plants may wilt, die and lodge above the infected area. Late in the season black irregularly shaped sclerotia about the size of a pin head form on and in the stem near the base. It is usually seen when there has been warm wet weather during flowering in spring.
In Lettuce the leaves the leaves wilt and the plant becomes limp.
Species Affected:
Brassicas, Beans, Cabbage, Capeweed, Cauliflower, Canola, Carrots, Celery, Dahlia, legumes, Lettuce, Lupins, Peas, Tomato and Potato are very susceptible.
Cereals, grasses, Beetroot, Onion, Spinach, Sweet Corn are resistant.
Biology:
Favoured by cool (10-250C), wet conditions and cultivation. Tolerates a wide temperature range.
Most common in autumn and spring on moist soils.
Tends to initially attack old or decaying leaves and tissue.
Sclerotia can survive for many years in the soil.
Often builds up on susceptible hosts such as Brassicas, legumes, Capeweed, Lettuce and Potato.
Spread by movement of soil containing spores.
It can produce wind dispersed spores.
Life Cycle:
Origin and History:
Distribution:
Significance:
Very damaging to Brussels Sprouts and Cabbage heads.
Management and Control:
Increase time between successive susceptible crops to 3-4 years. Intersperse with resistant species like cereals and grasses and avoid legumes (especially Lupins) and Capeweed.
Control weeds that may act as alternate hosts.
Destroy crop residues soon after harvest.
Deeply cultivate with mouldboard plough to bury sclerotia laden soil.
Avoid moving infected soil to cropping areas.
Maintain weed free conditions to reduce alternate hosts carrying the disease.
Space plants to reduce humidity.
Avoid watering during humid conditions.
Improve drainage.
Apply fungicides at the first sign of disease.
Lemon grass extracts reduce the disease (799).
Capsicums and Celery
Fumigate infected areas.
Carrots
Discard damaged Carrots
Store Carrots in cool, well-ventilated areas.
Lettuce
Destroy all infected crop residues.
Rotate with resistant crops.
Control alternate hosts in the crop and adjacent areas.
Apply fungicides at the first sign of disease.
Fumigate severely infested areas.
Lupins
Don't plant seed from crops with infected pods.
Don't sow Lupins for at least 3 years after a severe disease event.
Related and Similar Species:
Sclerotinia minor has sclerotia that are 1-2 mm long, oval to spherical and often clumped together.
References:
1206
1209
1205
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 for more information.