Bipolaris leaf spot of rubber

Bipolaris leaf spot is a fungal disease affecting rubber trees caused by the pathogen Bipolaris heveae. This disease primarily attacks the foliage of the plant, causing significant physiological stress and disrupting the normal photosynthetic activity essential for latex production.

The primary host for this fungus is Hevea brasiliensis. While it can affect trees of various ages, young plants and nursery seedlings are particularly susceptible due to the dense canopy structure and microclimate conditions that favor rapid fungal colonization.

Symptoms typically start as small, circular, or irregular lesions on the leaf surface. As the infection progresses, these spots expand, often developing a necrotic center and a chlorotic halo. In severe cases, the infected leaves undergo early senescence and drop, leading to premature defoliation of the tree.

The development and spread of Bipolaris heveae are heavily influenced by high humidity, rainfall, and moderate temperatures. The conidia of the fungus are easily dispersed by wind currents and water splashes, allowing the disease to move rapidly across plantations during the wet season.

Management of the disease relies on a multi-faceted approach. Key measures include the application of appropriate fungicides, ensuring adequate spacing between trees to improve air circulation, and rigorous sanitation practices, such as removing and destroying fallen leaf litter to reduce the primary inoculum load.