Phellinus noxius (Corner) Cunn.

Distribution

There are sporadic, sometimes serious, outbreaks of brown root disease in many rubber growing countries. Generally speaking, it is less serious than white and red root diseases. The distribution of the disease is noted in the 1998 Survey: it is especially severe in Côte d'Ivoire and India.

Symptoms

The foliage symptoms are similar to those for white root disease. As is the case with red root disease, the surface of roots infected with brown root disease is coarse as it is covered with a layer of soil. On close examination, brown rusty spots are visible which can be used to distinguish between brown and red root disease. In addition, if the bark of roots infected with brown root disease is peeled off, the surface of the roots will be seen to be covered with honeycomb-like structures. These structures are also visible inside the infected roots.

The fruiting bodies are smaller than is the case with the other root diseases and are hard with dark brown upper surfaces.

Disease spread

The method of spread is similar to white and red root diseases. In addition, brown root disease can also be disseminated by wind-borne spores. Spores lodge onto wounds on branches and trunks; roots can initiate infection and develop into a new source for disease spread.

Disease control

Proper clearing of land of old rubber is recommended to reduce the incidence of brown root disease. Wounds resulting from wind damage or pruning must be treated with wound dressing especially in areas where brown root disease is known to be present. Collar protectant dressing containing tridemorph is recommended for treatment of infected trees.