Sugarcane streak mosaic

The disease is characterized by the appearance of narrow, elongated, broken chlorotic stripes that run parallel to the leaf veins. These streaks are often pale green or yellowish.

As the infection progresses, these stripes may lengthen and coalesce, leading to a mottled or striped appearance across the entire leaf surface. This heavily interferes with the photosynthetic ability of the plant.

Infected plants exhibit stunted growth and reduced vigor. The stalks may become thinner, and internode length is often significantly reduced compared to healthy plants.

Severe infestations can lead to premature leaf yellowing and necrosis, particularly under environmental stress such as drought or high heat.

Visual identification is key, but confirmation is often required through laboratory testing like ELISA or PCR due to the similarity of symptoms to other physiological disorders.

The causative agent of the disease is the Sugarcane streak mastrevirus (formerly Mastrevirus sacchari), a member of the Geminiviridae family. It is a plant virus characterized by a single-stranded DNA genome.

The virus particles are classic geminate (twinned) capsids typical of the Mastrevirus genus. It primarily affects the vascular system, specifically the phloem, causing systemic infection.

The virus persists in wild grass hosts, which act as a reservoir throughout the year, allowing for continuous transmission when environmental conditions are suitable.

The primary vectors of the virus are leafhoppers, particularly those of the genus Cicadulina. These insects acquire the virus by feeding on infected sap and transmit it to healthy plants.

Once introduced into the plant, the virus moves systemically, ensuring that every newly developed leaf contains the pathogen, making recovery impossible.

The spread of the virus is heavily dependent on the population density of the insect vectors. Warm and humid climates favor both the reproduction of leafhoppers and their migratory activity.

Presence of weeds and secondary host plants around fields significantly increases the risk of early-season infection, as these areas provide a breeding ground for vectors.

The use of infected sugarcane setts (cuttings) for propagation is the most critical factor in spreading the disease over long distances and into new farming regions.

Agricultural practices that promote high humidity within the field canopy can also create favorable microclimates for the rapid multiplication of the viral vectors.

Continuous cropping and lack of proper field sanitation between seasons allow the pathogen to maintain a high inoculum level in the environment.

The economic impact of the disease is primarily realized through significant reductions in cane yield per hectare, as the viral infection severely weakens the plant's metabolic processes.

The sugar content (sucrose percentage) in the juice is often adversely affected, resulting in lower industrial efficiency and profitability for sugar mills.

Infected fields show uneven maturation and growth, which complicates the harvesting process and increases the costs associated with post-harvest sorting.

Susceptibility to secondary pests and diseases increases in infected stands, as the virus suppresses the natural defense mechanisms of the sugarcane plant.

Large-scale outbreaks can necessitate the complete destruction of infected planting material, causing immediate financial loss for the farmer and regional production declines.

The most important control strategy is the use of disease-free planting material, sourced from certified nurseries and tissue culture laboratories.

• Maintaining field sanitation by removing infected volunteer plants.
• Effective weed management to eliminate alternative hosts for the virus and vectors.
• Application of systemic insecticides to control leafhopper populations at the early growth stages.
• Breeding and planting of resistant or tolerant sugarcane cultivars.

Regular monitoring of the fields during the early stages of growth is essential for the early detection and removal of diseased plants, known as roguing, to prevent spread.

An integrated pest management (IPM) approach is vital, combining cultural practices, biological control, and limited chemical interventions to minimize the disease impact sustainably.