Phaeocytostroma iliau

The pathogen is characterized by the production of pycnidia, which are embedded within the plant tissue. These pycnidia serve as the reproductive structures, releasing conidia that facilitate the spread of the infection.

Mycelial growth occurs within the vascular bundles and parenchyma of the sugarcane stalk. This colonization disrupts the plant's physiological functions, particularly the transport of water and nutrients to growing points.

The fungus survives primarily on infected crop debris left in the field. Its ability to persist in the soil or in dead plant tissues makes it a difficult pathogen to manage once established in a production area.

Dissemination is largely mediated by splashing rain and water runoff, which carries the conidia to healthy young shoots, initiating new infection cycles during periods of high humidity.

The primary host is sugarcane, with young shoots being the most susceptible phase of development. The infection often leads to stunted growth and, in severe cases, the death of individual stalks.

A hallmark symptom is the physical binding of leaf sheaths around the stem. This "coiling" effect restricts the elongation of new leaves, leading to the distortion or death of the apical meristem.

Yield loss is significant, as the reduction in healthy stalks directly impacts the volume of harvestable biomass. Moreover, the quality of the juice is compromised due to poor sugar translocation.

The disease disrupts the uniformity of the plantation, creating gaps in the crop stand that allow for weed competition and further yield reduction.

In addition to primary damage, the weakened state of the plant makes it more susceptible to secondary infections by opportunistic pathogens, further accelerating the decay of the affected stalks.

Early symptoms include elongated, dark-gray to brownish lesions on the leaf sheaths that tightly wrap the stalk. As the disease progresses, these lesions merge.

The diagnostic sign of iliau is the cementation of leaf sheaths, where the infected tissues fuse together to form a hard, tight "cocoon" that prevents the expansion of the inner leaves.

Small, black, erumpent pycnidia are visible on the surface of the infected sheaths. These are the fruiting bodies that indicate the presence of the pathogen.

Internal examination of the affected stalks reveals reddish or darkened vascular tissues, which confirms that the infection has moved beyond the external sheaths.

• Dark necrotic lesions on leaf sheaths.
• Leaf sheaths cemented around the stalk.
• Distorted or stunted top growth.
• Visible black pycnidia on stems.
• Internal discoloration of vascular tissues.

The use of disease-free planting material is the most critical management step to prevent the introduction of the fungus into new areas.

Sanitation practices, such as the removal and destruction of crop residues after harvest, are essential to reduce the inoculum load in the field.

Crop rotation with non-host species is highly recommended to starve the pathogen and reduce its population levels in the soil over several growing seasons.

Selecting and breeding for resistant sugarcane cultivars is the long-term solution for managing iliau disease, providing stable protection for the crop.

Improving field drainage can help create an environment less favorable for the spread of spores, as high moisture is a key factor for the successful infection and colonization by the pathogen.