Terminal stunt of cotton

The characteristic sign is the shortening of internodes, resulting in a rosette-like appearance of leaves at the top of the plant.

Leaves may show significant chlorosis, curling, and abnormal development, often becoming brittle as the disease progresses.

Affected plants suffer from extensive shedding of buds and flowers, leading to a drastic reduction in boll formation and total yield.

As the disease advances, the plant may initiate proliferation of side shoots, creating a bushy, broom-like look while the main stem ceases vertical growth.

The causal agent of terminal stunt is typically a phytoplasma, a specialized type of bacteria that inhabits the plant's phloem tissue.

The disease is vectored by leafhoppers of the family Cicadellidae, which acquire the pathogen while feeding on infected plant sap.

Once ingested by the leafhopper, the phytoplasma multiplies within the insect, ensuring it remains an infective vector for the rest of its lifespan.

Transmission occurs when these infected insects move from weed hosts or neighboring fields to healthy cotton plants during feeding sessions.

The phytoplasma remains systemic within the cotton plant, affecting its physiological processes and disrupting normal hormonal balance throughout the season.

Environmental conditions that favor the proliferation of leafhopper populations are key factors in the spread of terminal stunt.

Warm and humid weather conditions stimulate both the reproductive cycle of the vector and the development of the infection within the plants.

The presence of wild grasses and weed hosts surrounding cotton fields serves as a primary reservoir for both the phytoplasma and the leafhopper vectors.

Poor agricultural practices, such as excessive fertilization that leads to succulent, attractive foliage, can increase leafhopper feeding activity.

Dry periods that force insects to migrate from dried-out pastures to irrigated cotton crops often trigger sudden outbreaks of the disease.

Terminal stunt causes significant economic damage to the cotton industry by drastically reducing the number of bolls produced per plant.

The quality of lint harvested from stunted plants is substantially inferior, failing to meet trade standards for maturity and length.

Early-season infections can lead to total crop failure on localized patches, requiring replanting or resulting in significant financial loss.

Beyond direct yield loss, the cost of frequent insecticide applications required to control the vector adds a burden to operational expenses.

Seeds harvested from heavily infected plants often show poor viability, making them unsuitable for use in future planting seasons.

Integrated Pest Management (IPM) is essential, focusing primarily on controlling the leafhopper vector using targeted insecticidal sprays.

Sanitation practices, including the removal of weeds and alternative host plants around the field boundaries, are critical to reduce the inoculum source.

Choosing resistant or tolerant cotton cultivars is the most sustainable approach for managing the risk of terminal stunt in endemic areas.

Maintaining spatial isolation between cotton fields and other host crops helps in preventing the massive influx of vectors.

• Regular monitoring using sticky traps to assess leafhopper population dynamics.
• Applying systemic insecticides during early vegetative growth to prevent initial colonization.
• Promoting healthy soil and crop nutrition to help plants withstand secondary physiological stress.