DISTRIBUTION

IRRDB surveys indicate that this disease is present in most rubber growing countries. It is serious in India, Indonesia, Malaysia, Philippines and Thailand but not in Sri Lanka. It is unimportant or unknown in China and the producing countries of Africa and South America. For the results of the 1998 Survey.

SYMPTOMS

Corticium salmonicolor attacks the main stem and branches, the most common site of infection being the fork of the tree. The initial symptom is the exudation of drops of latex from infected bark which drip or run along the stem. Later, white silky threads of mycelium develop on the surface of the bark forming a "cobweb". Under favourable conditions, the lesions turn light pink in colour with more intense bleeding of latex. The infection may spread up the branches and down the main stem of the tree causing the foliage above the point of infection to wilt and die. Later, after the disease appears to be inactive, side shoots can be seen growing below the dead portion of the stem. When weather conditions favour another attack, the disease recurs, killing the new side shoots. The final effect of pink disease is the prolongation of the immaturity period owing to severe retardation of growth.

DISEASE SPREAD

The fungus produces two types of spores: basidiospores and necator spores. These spores, which are blown by wind and dispersed by rainsplash, spread the disease. The disease is more prevalent in areas with high rainfall. The disease is not a problem on mature trees, and trees which are between one to eight years old are the most susceptible disease.

DISEASE CONTROL

Weekly spraying with Bordeaux mixture is recommended but should be undertaken only in the case of trees which are not in tapping owing to the deleterious effect of copper on the properties of latex. The Bordeaux mixture is prepared by mixing 1kg of copper sulphate, 2kg of slaked lime and 100 litres of water. The mixture should be used immediately. Normal knapsack sprayers or pneumatic sprayers are normally used but, if the attack is severe, motorized sprayers are better; these also permit the use of thicker formulations. Bordeaux mixture must be applied as long as the disease is apparent. A commercial product, tridemorph formulated in latex (Calixin-Ready-mixedR), can be used, brushed onto the lesions and extending to a few centimetres above and below the lesion. Normally one brushing during the disease season is sufficient . Other fungicides which can be used against pink disease are chlorothalonil and thiram. Chlorothalonil at 3% ai can be sprayed fortnightly. Chlorothalonil and thiram can also be formulated in bitumen or other base and applied by brushing.

Info first published: April 1994