Thermotherapy and meristem Culture - Conventionally, viruses are eliminated by thermotherapy of whole plants, in which plants are exposed to temperatures between 35-40°C for a few minutes to several weeks depending on the host virus combination. Thermotherapy is based on the fact that most viruses are killed at temperatures much below those, which kill their host plants.

Thermotherapy is usually effective against isometric and thread like viruses and against mycoplasmas, but is ineffective against many other viruses. Only a small proportion of plants survive heat treatment, and often these plants become susceptible to other diseases.

Thermotherapy is often combined profitably with meristem culture to obtain virus free plants. In general, shoot tips are excised from heat treated plants, and larger explants can be safely taken from such plants. Potato virus S (PVS) and potato virus X (PVX) are not eliminated either by thermotherapy or by meristem culture alone.