Tea is the most popular and inexpensive beverage produced from the young shoots of tea plant. Tea is grown in more than 50 countries, mostly in plantations. A large number of pathogenic organisms are specialized in attacking different parts of the plant. The crop loss in tea due to pests and diseases is around 10-15%. Among the stem diseases, collar/Phomopsis canker is very important. The disease is caused by the fungus Phomosis theae Petch, belongs to the Deuteromycetes. Although phomopsis canker is known for over 40 years in south India, the disease has become a major problem only in recent years as the estates now resort to large scale replanting infilling and inter row planting to increase production and productivity. Unfortunately, majority of the clones used for this are susceptible to the disease. Despite its importance, no effective measures have been worked out to control the disease.The biology of the pathogen and the etiology of the disease are also not known. It is in this scenario, the present investigation has been taken up. The clonal susceptibility, nature of the pathogen, it’s life cycle, host parasite interaction and control measures were studied.