Mottled stripe

The disease initially manifests as thin, elongated streaks on leaves that eventually appear as mottled, reddish-brown stripes.

These stripes are often characterized by irregular, broken edges, contrasting sharply with the surrounding green leaf tissue.

As the infection progresses, the lesions expand and necrotic areas develop, eventually leading to the death of the leaf blade section.

In highly susceptible cultivars, the disease can lead to extensive yellowing and necrosis, significantly impacting the leaf's photosynthetic capacity.

Under high humidity, a bacterial ooze may be observed on the surface of the lesions, which helps in the dissemination of the bacteria.

The causative agent of Mottled stripe is the bacterium Herbaspirillum rubrisubalbicans, a vascular pathogen affecting various grass species.

This bacterium is an endophytic organism capable of systemically colonizing the xylem and parenchyma tissues of the sugarcane plant.

It typically enters the plant host through natural openings like stomata or through mechanical wounds caused by tools or insect feeding.

The disease is classified as a bacterial necrosis, which can cause significant damage to the leaf structure if conditions are conducive.

The pathogen is known to persist in infected crop debris and in the stalks used for vegetative propagation, making control challenging.

The development of Mottled stripe is strongly favored by warm temperatures and periods of high rainfall or high relative humidity.

Optimal environmental conditions for bacterial multiplication are typically found in the temperature range of 25°C to 30°C.

Heavy rainfall facilitates the spread of the pathogen through rain splashes, which carry the bacteria from infected to healthy leaves.

Inadequate airflow within dense crop canopies creates microclimates that promote the persistence and spread of the bacterial pathogen.

Poor sanitation practices, such as the use of unsterilized harvesting tools, are primary drivers for the rapid spread of the disease within fields.

The economic impact of Mottled stripe is mainly seen in reduced biomass yield and stunted growth of affected sugarcane stalks.

By damaging the photosynthetic machinery, the disease reduces the plant's ability to store sucrose, leading to lower sugar recovery rates.

Chronic infections weaken the plant, making it more susceptible to environmental stressors and secondary pathogenic attacks.

The disease can cause significant losses in quality, affecting the overall financial viability of sugarcane production systems.

Severe infestations often require costly intervention or the replanting of entire fields with pathogen-free material.

Management begins with the use of resistant or tolerant cultivars, which is the most effective long-term strategy for disease suppression.

Strict quarantine measures and the use of pathogen-free, certified seed cane are essential to prevent the introduction of the bacteria.

Sanitary practices must be strictly enforced, including the regular disinfection of all harvesting equipment and tools.

Maintaining adequate plant spacing to improve air circulation helps to reduce leaf wetness duration, thus limiting bacterial infection.

Integrated disease management also involves specific field actions

• removing and destroying infected plants
• proper field sanitation after harvest
• monitoring for secondary insect vectors