Powdery mildew of teak

The disease is caused by the fungus Erysiphe tectonae, an obligate biotrophic pathogen. It belongs to the Erysiphales order, commonly known as powdery mildews. The fungus survives and reproduces on the surface of host leaves, forming hyphae and conidiophores that derive nutrients through specialized structures known as haustoria, which penetrate the plant cell walls.

The primary host for this pathogen is teak (Tectona grandis), a highly valuable timber species. The disease predominantly affects young leaves and succulent shoots, making it a significant concern for forest nurseries and juvenile plantations. While mature trees are less susceptible to severe damage, the cumulative effect of the disease in young stands can compromise the vigor of the entire plantation.

Symptoms begin as small, white, powdery patches on the leaf surface. As the fungus spreads, these patches expand to cover large areas of the foliage, giving the leaves a greyish-white dusted appearance. Infected leaves often curl, turn yellow, and undergo necrosis. In severe cases, premature leaf drop occurs, which drastically reduces the plant's photosynthetic capacity and slows down growth rates significantly.

The development of Erysiphe tectonae is heavily dependent on specific microclimatic conditions, notably high humidity and moderate temperatures. Dense canopy structures or overcrowded nursery conditions favor the disease by reducing airflow and maintaining moisture on the leaf surfaces. Spores are primarily disseminated via wind currents, allowing the pathogen to move rapidly through susceptible populations.

Integrated management is essential for controlling this pathogen. Growers should prioritize the selection of resistant teak clones and maintain proper spacing between trees to ensure adequate air circulation. In nursery settings, regular monitoring and the use of targeted fungicides can prevent large-scale outbreaks. Sanitation practices, such as removing infected debris, help reduce the overall inoculum load in the plantation area.