Cashew bunchy top

Leaves on the affected branches show significant size reduction, display chlorosis, and often exhibit curling along the margins.

The plant exhibits excessive development of auxiliary buds, creating a bushy growth habit that deviates from the normal tree architecture.

During the flowering stage, inflorescences become distorted and may show phyllody, where floral parts revert to green leaf-like structures.

Over time, the terminal shoots show dieback symptoms, leading to the gradual decline and eventual death of the entire tree canopy.

The causative agent of Cashew bunchy top is a phytoplasma, a specialized wall-less prokaryote that colonizes the plant's phloem tissue.

These pathogens are obligate parasites, meaning they cannot survive outside the living tissues of the host plant or the insect vector.

Transmission occurs primarily through insect vectors, specifically leafhoppers (family Cicadellidae) that feed on the phloem sap of infected trees.

Once the insect acquires the phytoplasma while feeding, it remains capable of transmitting the pathogen to healthy plants for the rest of its life.

The spread of the disease is strictly dependent on the movement and feeding patterns of these insect vectors within the plantation environment.

The incidence of the disease is highly dependent on the population density of the insect vectors present in the cashew growing region.

Warm and humid tropical conditions are optimal for the rapid reproduction of leafhoppers, significantly increasing the risk of infection outbreaks.

The presence of alternative host plants in the surrounding ecosystem acts as a reservoir for the phytoplasma, ensuring its survival year-round.

High-density planting configurations without sufficient airflow can facilitate the rapid migration of vectors between adjacent cashew trees.

Poor orchard sanitation, including the presence of weeds, provides critical shelter for insect vectors during periods when cashew trees are not flushing.

Cashew bunchy top is a destructive disease that can lead to severe economic losses by rendering infected trees completely unproductive.

The disease severely disrupts the plant's translocation of nutrients, causing metabolic exhaustion and long-term decline in tree vitality.

Affected trees struggle to support fruit development, leading to floral abortion and failure to produce marketable nuts.

In mature plantations, the disease can spread rapidly, forcing growers to remove and replace entire sections of the orchard to stop the epidemic.

Because there is no known cure for established phytoplasma infections, the disease represents a significant threat to sustainable cashew production.

Effective management begins with strict phytosanitary practices, including the immediate removal and destruction of symptomatic trees.

Regular insecticide applications are necessary to manage the population of leafhoppers and minimize the spread of the pathogen to healthy plants.

Maintaining a clean orchard floor by removing weeds reduces the habitat available for insect vectors and helps lower infection pressure.

Growers should prioritize the use of high-quality, certified disease-free planting material to prevent the introduction of the pathogen.

• Monitor orchard frequently for early signs of rosette growth.
• Prune and burn infected plant parts to reduce the inoculum load.
• Establish spatial isolation between young plantations and older orchards.