Charcoal rot

Figure 1: Wilting strawberry plant

Figure 2: Internal crown and vascular rot

Figure 3: Microsclerotia in a strawberry crown

Cause

The fungus Macrophomina phaseolina.

Symptoms

• Plants exhibit wilting symptoms, drying and death of older leaves (Figure 1).
• Younger leaves will persist initially but will eventually collapse.
• When crowns are cut open longitudinally, dark brown necrotic areas in the internal cortex and the vascular tissues can be seen (Figure 2).

How it spreads

The pathogen produces microsclerotia (Figure 3). These are tiny, round fungal structures that allow the pathogen to survive in soil or in infected material for a very long time. Microsclerotia are released in the soil as the plant material decomposes.

The pathogen invades the plant through roots and crown.

High soil temperatures (higher than 27^oC) favours the fungus.

Incorporating diseased plants back into the soil may increase the population of the pathogen in the soil and lead to further infection in the next crop. Moving soil can also spread the pathogen.

Crops affected

Symptoms of charcoal rot are similar to those caused by other soil-borne pathogens. Have affected plants tested by a diagnostic laboratory so you can apply appropriate management options.

There are no fungicides registered for charcoal rot of strawberry in Australia.

You can:

• remove diseased plants to minimise inoculum in the soil
• fumigate the soil
• use tolerant varieties
• avoid movement of infected soil.