Plant viruses in irrigation water: reduced dispersal of viruses using sensor-based disinfection

The increasing use of recirculating nutrient solutions and drainage water for irrigation purposes requires effective sanitation methods to minimise the dispersal of plant pathogens. Among these, plant viruses are of particular interest because they cannot be cured. A new disinfection system was tested in regard to its ability to inactivate plant viruses in nutrient solution in greenhouses. Potassium hypochlorite produced onsite by an electrolytic disinfector and injected once weekly into the nutrient solution by a sensor, prevented the dispersal of Pepino mosaic virus in the tomato crop. The management program assures that virus particles released from infected plants do not accumulate, forming an infectious virus reservoir which represents an inoculum potential in the hydroponic system. Both tested applications at 0.2 or 0.5 mg free chlorine/l nutrient solution for 60 or 30 min ensured virus inactivation and did not cause phytotoxicity. The yield of tomato plants grown in KCIO-treated nutrient solution was even significantly higher than that of control plants. PepMV-infected source plants solely bore unmarketable tomatoes showing discoloration. By inhibiting the dispersal of PepMV and the infection of test plants, the amount of unmarketable tomato fruits was reduced rigorously in treated variants.