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Sclerotium rolfsii

Symptoms & Signs

 

sclerotium

Sclerotium rolfsii (fungus) often referred to as Southern Blight (in the Southern U.S.) causes a crown rot disease of Ajuga, Hosta, Iris and other ornamentals. This disease can cause severe damage and is difficult to eradicate. Typically restricted to warm, humid states in the Southern U.S. crown rot appeared in many Midwest (Iowa) gardens in the mid 1990s. How severe the disease may be in Colorado remains to be seen. More than likely, in dry landscape situations the disease will not be a problem. However, in the nursery, greenhouse or in humid landscape microclimates, the disease has the potential to cause damage. Growers receiving perennials from other States may want to check plants for telltale signs and symptoms.

sclerotium
Symptoms:


Lower leaves of infected plants begin to wilt and may turn yellow or brown.


Signs:


Tiny white strands or threads called mycelium (body of the fungus) may be present at the base of the plant. Look closely for small tan spheres, about the size of mustard seeds. These are called sclerotia and serve as the over wintering and reproductive structures of the fungus. The sclerotia may be confused with fertilizer pellets, but are usually smaller in size and grow at the base of the plant.


 

Susceptible Herbaceous Perennial plants

Susceptible Herbaceous Perennial plants: (this is not a complete listing)

Latin name
Common name

Ajuga

bugleweed

Anemone

windflower

Aquilegia

columbine

Arrhenatherum

Oat grass

Asplenium

Dragontail fern

Caladium

Fancy-leaved caladium

Campanula

Bellflower

Chrysogonum

Golden star

Convallaria

Lily of the valley

Dicentra

Bleeding heart

Digitalis

Fox glove

Hemerocallis

Day lily

Hosta

Plantain lily, Hosta

Lysimachia

Loosestrife

Phlox

Phlox

Ranunculus

Buttercup

Vinca

Periwinkle

Viola

Pansy, violet

 

Management


Management of the disease will occur only through:

  • Immediate removal and destruction of infected plants

  • Use of pasteurized potting media

  • Adequate drainage and avoidance of over irrigation

  • Use of pathogen free stock

There are a few fungicides labeled for control of this disease. They are used to suppress S. rolfsii.

  • Contrast (flutolanil)

  • Terraclor, Defend, Pennstar, Revere, and PCNB (all contain PCNB)

  • Since phytoxoicity may result to PCNB, test it on a small scale before attempting larger-scale treatments.



If a chemical is used, be sure to follow manufacturers directions.


 

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