With increasing interest in natural products of plant origin for medicinal and health care benefits there is added emphasis on the quality of the source raw material. In most cases the vegetative tissues and organs are the source of the required raw material. However, such tissues/organs may become infested/susceptible to many diseases causing deterioration of the quality of the desired economic product and loss of genetic resources. Considerable progress has been made with respect to the identification of disease causing organisms, and their pathogenic impact at organ, cellular and biochemical level. This review focuses on various diseases caused by bacteria, fungi, nematodes, viruses and phytoplasmas threatening the yield, biomass, bioactive potential of medicinal and aromatic plants of the sub-tropics. Several studies suggest that management of diseases through biological measures is more effective to check multiple diseases. Necessary management strategies for efficient disease management to realize quality raw material and enhanced metabolite productive potential have been outlined.