Apples with fire blight: one reason you should disinfect pruning sheers. Photo by Peggy Greb

Neighbor Anne tipped me off to an interesting fact sheet on disinfecting pruning sheers by Dr. Linda Chalker-Scott, a horticulture professor at Washington State University. I’ve been using bleach which, it turns out, is not the best choice.

Bleach is both toxic to humans and to plants as well. It also stains clothes and damages tools. Chalker-Scott’s preferred alternative? Lysol. It won’t corrode your tools and is safer to humans. She also discusses alcohol and Lysterine and a few other choices.

The fact sheet concludes with more important details:

• Be sure to clean tools of dirt, debris, etc. before disinfecting.
• After dipping your pruning tools, be sure to wipe away excess disinfectant to avoid injuring
the next plant.
• A longer soaking may be needed for pruning surfaces that are not smooth.
• Like pruners, increment borers should always be sterilized before and after use.
• Never use disinfectants on pruning wounds; they are phytotoxic and cause more harm than good.

(Why do you need to disinfect pruning tools? Because if you don’t, you can transmit disease such as fire blight and dutch elm disease from one tree to the next. It’s best to clean your tools between each tree or shrub as you work. We do this as a matter of course, whether we think a plant is diseased or not. It’s like practicing safe sex.)

For more horticultral myths, see Chalker-Scott’s myth page.