Okra yellow mosaic virus

Affected plants show severe deformation of leaf blades, which may curl, become stunted, or exhibit atypical shapes. Growth is noticeably retarded, with shortened internodes resulting in dwarfed, weak bushes.

On reproductive organs, the disease manifests as a reduction in the number of flower buds and their premature abscission. If fruits do set, they often appear pale, deformed, mottled, and lose their marketability.

As the disease progresses, affected areas of the leaf may turn almost entirely yellow or creamy, with only the main veins remaining green. This symptomatology severely impacts the plant's physiological state.

The severity of symptoms depends on the plant's age at the time of infection: early infestation leads to complete growth cessation and total crop loss.

The causal agent is Begomovirus abelsmoschusomanense, a virus belonging to the Geminiviridae family. It is a single-stranded circular DNA virus transmitted by specific vectors in tropical and subtropical climates.

The primary vector for this pathogen is the tobacco whitefly (Bemisia tabaci). The insect acquires the virus by feeding on the sap of infected plants and retains the ability to transmit it throughout its entire lifespan.

Transmission occurs through a persistent mode: after acquiring the viral load, the whitefly requires a latent period to allow the virus to accumulate in its salivary glands before it can infect healthy plants.

The virus primarily affects okra (Abelmoschus esculentus), causing a systemic disease that spreads throughout all plant organs, including roots, stems, and fruits.

In addition to okra, the virus host range may include associated weeds in the Malvaceae family, which serve as reservoirs for the infection during the off-season.

The spread of the virus is directly linked to whitefly population density. High air temperatures and moderate humidity create an optimal environment for the rapid reproduction and migration of these insect vectors.

A critical factor is the proximity of infection sources, such as old okra plantings or wild weeds. In these areas, whiteflies build up a significant viral load before migrating to younger crops.

Drought periods promote increased pest numbers, as plant stress makes them more susceptible to viral agents and the feeding activities of sucking insects.

Poor agricultural practices, such as lack of crop rotation and failure to control weeds in a timely manner, allow the virus to persist in the field throughout the growing season.

Whitefly migration can occur over significant distances via wind currents, ensuring rapid virus spread between adjacent fields and greenhouses.

Okra yellow mosaic virus causes massive economic losses, as infection of young plants can lead to 80–100% crop loss. Product quality is severely degraded to critically low levels.

Infection leads to metabolic disruptions, reduced biomass accumulation, and premature senescence of the plant. As a result, the plant loses its ability to sustain a productive harvest period.

Fruit marketability is ruined due to mottling and twisting, making them unsuitable for both fresh markets and processing. The harvest becomes economically unviable.

The disease facilitates secondary infection of weakened plants by pathogenic fungi and bacteria, further complicating field management and requiring complex diagnostic efforts.

Mitigating the impacts of the infection requires significant financial investments in chemical insecticide applications and the replacement of severely affected plots.

The key preventive strategy is managing the whitefly population. Applying systemic insecticides during the early stages of crop development helps reduce the risk of viral transmission from the vector to the plant.

The use of resistant varieties and hybrids remains the most effective protection method. Breeding programs focus on developing plants with genetic immunity to specific Begomovirus species.

• Regular removal and destruction (burning) of infected plants.
• Maintaining spatial isolation between old and young plantings.
• Using yellow sticky traps to monitor whitefly population levels.
• Eliminating weed reservoirs around the field perimeter.

Timing of planting is crucial; sowing dates can be adjusted to avoid peak whitefly activity during the most vulnerable growth phases of okra. Earlier plantings often suffer less from outbreaks.

Utilizing non-woven floating row covers during the first few weeks after emergence helps physically block whitefly access to young plants, protecting them during their most vulnerable period.