Sanitizing Pruning Tools - January 31, 2018
Jeff Schalau, Agent, Agriculture & Natural Resources
University of Arizona Cooperative Extension, Yavapai County

As I conduct my deciduous fruit tree pruning demonstrations in cooperator orchards, I am always mindful of the potential for disease transmission and have always sanitized my tools with 70% isopropyl alcohol. I simply carry a bucket with a smaller bucket of isopropyl alcohol in it. I leave the loppers and hand pruners with the blades soaking in it while pruning. At a recent demonstration, an attendee asked about using Lysol for this purpose. At one time, I used a 10% bleach solution, but this was very corrosive on my tools. Lysol seemed like a good idea, so I began poking around for more information on the topic.

Most Cooperative Extension Fact Sheets, including my own, recommend using isopropyl alcohol or a dilute bleach solution to sanitize pruning tools. They also recommend leaving them to soak for 2-5 minutes between trees – especially when you see evidence of disease or decline in the trees. I searched on-line for science–based information. When readers do this, I hope you place your trust in “.edu” websites rather than “.com” sites. Like previous fact-finding missions, I arrived at an excellent publication by my Washington State University colleague, Dr. Linda Chalker-Scott. Dr. Chalker-Scott conducted a literature review of peer-reviewed science and synthesized her findings, some of which I share here. Her factsheet, “Sterilized Pruning Tools: Nuisance or Necessity?” is linked below.

In Yavapai County, one pathogen that poses significant risk of spread by pruning tools between apples, pears, and a few other members of the Rosaceae family is fire blight (Erwinia amylovora). This bacterial disease infects flowers in the spring killing new shoots and can form cankers (discolored, sunken or raised areas) on stems of susceptible plants. Several researchers noted that fire blight is not transmitted during the dormant season – only during the growing season. Other diseases (bacterial spot, Cytospora canker, and some viruses) are readily transmitted by pruning tools during the dormant season. Each of these pathogens were more transmissible when favorable environmental conditions were present, but this research makes a strong case for sanitizing pruning tools to minimize spread of pathogens.

Disinfectants tested by various researchers were: alcohol (ethanol and isopropyl alcohol), chlorine (bleach and monochloramine), household cleaners (Listerine, Lysol, and Pine-Sol), and trisodium phosphate (10% solution). All were shown to be effective but with varying advantages and disadvantages. One of the studies also examined the corrosiveness of several products and found that Lysol was least corrosive and bleach was most corrosive

Dr. Chalker-Scott’s conclusions from this literature review were: 1) know your pathogen and its life history, and use common sense; 2) disinfect your tools when working in areas where viruses, viroids, vascular fungus, or bacteria; 3) avoid cutting active, oozing cankers; wait until they dry; 4) if you are pruning irreplaceable plants, always disinfect your tools; and 5) choose a disinfectant treatment that has been shown to be effective through published research. Dr. Chalker-Scott went on to say that she would probably not use alcohol but one of the common household cleaners at full strength. Dr. Chalker-Scott is a highly respected, Extension Horticulture Specialist from Washington State University with a long history of “myth busting”. I highly recommend her publications and books – she always cites the studies where she obtained information and makes her arguments with support from peer-reviewed science.

For a short time, I used Lysol disinfectant as a sanitizing solution, but could not stand the smell and the “slippery” feel of Lysol. I went back to 70% isopropyl alcohol. In a situation where no disease symptoms are evident, sanitize your tools for three to five minutes before pruning and between plants. Plants showing symptoms of disease should be pruned last or even deferred to a later time if slimy bacterial ooze is visible. Tools should be sanitized well before starting on the diseased plants. Start on the areas of the diseased plant where no symptoms are visible. Once you are pruning diseased areas, sanitize your tools more often. If a plant overwhelmed by disease and seems unproductive, consider removing it. I have also linked a photo of fire blight on apple and a publication on fireblight to the online edition. Happy pruning!

Naming of companies or products is neither meant to imply endorsement by the author nor criticism of similar companies or products not mentioned.

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Fire blight on apple stem. Note the visible canker and dead stem at the site of infection (from: Forestry Images, provided by Penn State Department of Plant Pathology & Environmental Microbiology Archives).

Additional Resources

Sterilized Pruning Tools: Nuisance or Necessity?
Dr. Linda Chalker-Scott Washington State University Puyallup Research and Extension Center

Fire Blight
University of Arizona Cooperative Extension

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Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr. #C
Prescott, AZ 86305
(928) 445-6590
Last Updated: January 22, 2018
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