Sandal spike disease

These organisms are wall-less bacteria that inhabit the phloem tissue of the host plant, effectively disrupting the translocation of essential nutrients and photosynthetic products.

The transmission of the disease in nature occurs primarily through insect vectors, specifically leafhoppers such as Nephotettix virescens, which spread the pathogen while feeding.

Additionally, the phytoplasma is transmitted through root grafts, where the root systems of infected and healthy sandalwood trees become physically interconnected in the soil.

The pathogen triggers severe hormonal imbalances in the tree, leading to the inhibition of apical dominance and the abnormal development of dormant axillary buds.

The most distinctive symptom is the progressive reduction in leaf size, where leaves become thin, stiff, and narrow, resembling spikes or needles.

Internodes are drastically shortened, resulting in the clustering of leaves into tight rosettes at the tips of branches, which gives the tree a spike-like appearance.

Affected trees exhibit severe chlorosis, with foliage turning pale or yellowish, followed by a gradual decline in canopy density.

Flowering and fruit set are completely suppressed, and the root system eventually undergoes necrosis due to the lack of metabolic support from the leaves.

The condition is chronic and inevitably fatal, leading to the death of the tree within one to three years after the onset of initial symptoms.

Sandal spike disease is considered the most devastating pathology for Santalum album, causing massive economic losses in the sandalwood industry.

Because the disease spreads rapidly through root contact, it can decimate entire plantations or forest stands in a relatively short period.

The infection prevents the synthesis of sandalwood oil within the heartwood, rendering the affected trees worthless for commercial harvest.

The disease poses a significant challenge to silviculture, as there are currently no effective large-scale therapeutic treatments available for infected mature trees.

Its persistence in wild and cultivated populations threatens the biodiversity of sandalwood forests, necessitating strict containment and monitoring measures.

The primary control strategy involves the immediate identification and eradication of infected trees, including their roots, to prevent the pathogen from spreading to healthy neighbors.

Implementation of buffer zones through deep trenching or tree removal is essential to physically break root grafts and stop the progression of the disease.

Managing insect vector populations via systematic insecticide applications during peak activity periods can help reduce the frequency of new primary infections.

Ongoing research focuses on the breeding and selection of sandalwood genotypes that demonstrate natural resistance to the phytoplasma infection.

• Strict quarantine regulations for the movement of nursery stock.
• Regular inspection of sandalwood plantations for early detection.
• Removal of alternative host weeds that may harbor the leafhopper vectors.