Evaluation of disinfectants to control mechanical transmission of tomato viruses and viroids in greenhouse tomatoes

Greenhouse tomato production has increased significantly in recent years. The cultural practices and intensive hands-on activities implemented in protected culture tomato have created ideal conditions for a number of plant pathogens to be mechanically transmitted. In some situations disease outbreaks have occurred resulting in serious epidemics as well as growers taking on huge financial losses. Planting tomato seed which has been properly tested for the key seed-borne/seed transmitted pathogens is a very important prevention measure. However, mechanical transmission of pathogens during crop production is a critical point in disease management. In this study, we aimed to evaluate the efficacy of disinfectants to prevent viral disease spread, using Pepino mosaic virus (PepMV), Tomato mosaic virus (ToMV) and Potato spindle tuber viroid (PSTVd) as experiment targets. Evaluation was conducted through mechanical inoculation on tomato seedlings using 16 chemicals/commercial disinfectants. The exposure time between inocula and disinfectants was designed for 0-10 s (immediately after treatment), 30 s, and 60 s before inoculation. Infection rate was determined 3-6 weeks post inoculation through symptom observation and appropriate lab tests. Experiments were repeated 3-4 times for each pathogen. Preliminary results showed that (1) Clorox regular bleach, Virkon S, non-fat dry milk, Lysol cleaner, and Octave eliminated PepMV infection; (2) Clorox regular bleach, Virkon S, non-fat dry milk, Lysol cleaner and Menno-Ter Forte eliminated ToMV transmission; and (3) Clorox regular bleach, Virkon S, and non-fat dry milk degraded the PSTVd infectivity. Among those effective disinfectants for each pathogen, Virkon S, Clorox regular bleach, and non-fat dry milk eliminated both virus and viroid transmission. Additional trials are underway to evaluate the efficacy of disinfectants on treating cutting tools to prevent virus spread.