How do I sanitize my pruning shears?

Question:

How do I sanitize my pruners and other garden tools to prevent the spread of disease?

Answer:

Proper cleaning and sanitization of pruners and other garden tools is important to prevent the spread of disease issues.  At minimum when removing disease-infected plant material, pruners should be disinfected between plants.  Ideally, they would be disinfected between each cut.

Several products are available for disinfecting pruning equipment.  Always remove dirt, sap, and other debris from pruning equipment before disinfecting.

Alcohol

One of the easiest ways to sanitize pruning equipment is to use ethanol or isopropyl alcohol. To sanitize with alcohol, wipe or dip the tool into the alcohol.  No prolonged soak is needed.  Rubbing alcohol (70% isopropyl alcohol) and ethanol are readily available at most drug stores and other retail outlets and can be used directly from the container with no dilution required. Disinfecting with alcohol is preferred for homeowners over most other methods because it is easy to use, readily available in stores, relatively inexpensive, does not require prolonged soaking, and isn't as corrosive to tools as bleach and TSP.

Some studies have shown that rubbing alcohol may not effectively disinfect pruning tools from certain plant pathogens.  For this reason, alcohol is not recommended for use in disinfecting pruning tools used on apple trees infected with fire blight. Utilize a bleach solution instead.

Bleach

A 10% solution of household chlorine bleach can be used as a disinfectant.  Prepare the solution by mixing 9 parts water with 1 part bleach.  Always add bleach to water (not water to bleach to avoid splashing) and protect skin and clothing from the bleach solution.  Use the solution within two hours of preparing it.  Soak pruning blades for at least 10 minutes in the solution, then rinse the tool with clean water to prevent corrosion.  

Household Disinfectants

Household disinfectants like surface wipes, cleaners, and sprays (i.e. Lysol, Pin-Sol, Clorox wipes, Microban, etc) may be used to sanitize pruning blades.  They are very effective at killing bacteria and other pathogens that cause human disease on surfaces and equipment in hospitals and schools, but their effectiveness against plant pathogens on garden equipment has not been well evaluated. At least one study has shown effective control of certain fungal plant pathogens using the disinfectant commonly found in surface wipes (quaternary ammonium compounds), but they did not kill all types of plant pathogens.

It is likely that these products can be effective at disinfecting pruning equipment, but other sanitizing solutions (such as alcohol) are preferred because the formulations and active ingredients of household cleaners can vary by product, and their efficacy on pruning equipment is not well known.  

TSP (Trisodium Phosphate) Cleaners

TSP cleaners (often sold as deck or siding cleaners) can be used to disinfect pruning equipment when diluted to 10%.  Prepare the solution by mixing 9 parts water with 1 part TSP.  Handle the cleaner carefully and prevent skin contact with undiluted TSP.  Soak the pruning blades in the solution for 3 minutes and rinse with clean water.  TSP products can be very corrosive and are more corrosive to pruning blades than bleach. This method of disinfection is not widely recommended for home gardeners because of the corrosive and toxic nature of these materials.