Marasmius sacchari

Marasmius sacchari is a fungal pathogen within the Marasmiaceae family. It is best known in agronomy as the causative agent of root and stem rot in sugarcane, particularly in tropical environments where moisture levels are high.

The fungus is characterized by the production of small, umbrella-shaped fruiting bodies that emerge from the base of infected stems. Beneath the soil, it survives as a network of mycelium that can persist on decaying plant debris for extended periods.

It is classified as a facultative parasite, meaning it can live as a saprophyte on dead organic matter while retaining the ability to infect living tissues of the host plant when conditions become favorable.

Spore dispersal occurs via wind and water splashes, allowing the fungus to spread rapidly across plantation rows. Once spores land on susceptible tissue, they germinate and penetrate the plant's epidermis.

This pathogen is highly resilient due to its ability to form rhizomorphs, which are specialized fungal structures that allow the organism to survive harsh environmental conditions and remain viable in the soil.

The primary host of Marasmius sacchari is sugarcane (Saccharum officinarum). The fungus attacks the root system and the lower nodes of the stalk, leading to significant physiological stress for the plant.

By damaging the root cortex and invading the stem, the pathogen interferes with the plant’s ability to uptake water and essential minerals. This results in stunted growth and a failure to reach full maturity.

Economic damage is substantial, as the fungus negatively impacts sucrose accumulation. Infected stalks have a significantly lower sugar content, making them unfit for efficient processing in sugar mills.

Severe infestations weaken the structural integrity of the crop, causing stems to become brittle and prone to lodging. This makes harvesting difficult and often results in heavy yield losses during the cutting process.

In addition to direct damage, the fungus facilitates the entry of secondary pathogens, such as bacteria, which accelerate the decomposition of the stalk, leading to complete crop failure in localized areas.

Early symptoms include yellowing and premature death of the lower leaves. As the root system is compromised, the plant shows signs of wilting even when soil moisture appears to be adequate.

White mycelial growth is often visible around the base of the stalks near the soil line. Under humid conditions, small white or cream-colored mushrooms (fruiting bodies) develop, which are definitive signs of active infection.

Internally, the stem tissue exhibits reddish-brown discoloration and rot. The vascular bundles may appear damaged, and the pith can become dry and fibrous as the fungus consumes the cellular contents.

Plants affected by this pathogen are easily pulled from the ground because the root structure has been severely weakened or destroyed. In advanced cases, the entire root ball may appear decayed.

Patches of stunted plants within a field often indicate the presence of the fungus, as the disease spreads radially from an initial point of infection through the soil or via contact between root systems.

Effective management begins with the use of disease-free planting material. Growers should ensure that sugarcane setts are sourced from healthy fields and undergo thorough inspection before being introduced to a new area.

Heat treatment, specifically soaking sugarcane setts in hot water, is a standard agronomic practice to eliminate fungal mycelium living within the tissues of the planting stock.

Crop rotation is crucial. By rotating sugarcane with non-host crops, farmers can starve the fungus of its host, thereby reducing the inoculum load in the soil over time.

Good field drainage and proper soil aeration help create an environment that is less conducive to fungal growth, as excessive moisture promotes the spread of mycelium.

• Field sanitation to remove and burn infested crop residue.
• Application of systemic fungicides during the planting stage.
• Selecting resistant or tolerant sugarcane varieties for cultivation.
• Minimizing mechanical damage to roots during cultivation practices.