Plant diseases, caused by pathogens such as bacteria, viruses and fungi, can easily be spread from one plant or tree to another if pruning tools are not disinfected before use.
Sap from trees and plants usually sticks to the blades of secateurs, loppers, saws and other pruning tools. Any infected sap can transfer diseases to the next plant or tree through pruning cuts.
The bacterial disease crown gall, caused by Agrobacterium tumefaciens, which produces tumour-like swellings on the bark of trees and plants, particularly members of the Rosaceae (rose) family such as roses, raspberries, almonds, cherries, peaches, pears and apples, and eventually kills them, is most commonly spread through pruning tools that have previously been used on infected trees and plants.
Pruning tool hygiene is an important disease-prevention practice. After finishing pruning a plant or tree, always disinfect pruning tools before moving onto the next one.
Additionally, cleaning off plant residues and sap from pruning tools stops the blades from gumming up and jamming, and also prevents rusting of the blades. Clean blades cut better and last longer!
What is the Best Disinfectant to Use to Sterilize Pruning Tools?
Various alcohol solutions, such as ethanol (methylated spirits), or isopropyl alcohol (rubbing alcohol) with a concentration of at least 70% alcohol can be used for disinfecting pruning tools.
Methylated spirits contains a minimum of 95% alcohol, and commercial grade isopropyl alcohol purchased from paint stores contains 99.97% alcohol. These can be diluted to approximately 75% alcohol by mixing 750ml of alcohol with 25% water, to make 1 litre of solution, or simply put, 3/4 alcohol mixed with 1/4 water.
If lower concentrations of alcohol are only available, such as 70% to 75%, do not add water, use them as they are, undiluted.
Why dilute the alcohol? For alcohol to be an effective disinfectant, in needs to be in contact with a surface or item for at least 30 seconds. The reason not to use pure (100%) alcohol is because evaporates too quickly for this purpose. If the concentration of alcohol is less than 70%, it’s too weak to effectively kill disease-causing pathogens.
Solutions of 70% – 75% alcohol must be kept in a sealed bottle to prevent evaporation, and can be stored, as the potency doesn’t fade away over time.
A handy way to use alcohol for disinfection is to put it into a spray bottle, and a 500ml (0.5 litre) spray bottle is a convenient size. In a 500ml bottle, add 375ml of 100% alcohol and 125 ml of water. Shake to mix and it’s ready to spray.
How to Clean Pruning Tools with Alcohol
Pruning tool blades can either be dipped, wiped or sprayed with alcohol solution before moving from one plant or tree to the next.
In my experience, the most effective way to clean the blades of pruning tools is as follows:
- Spray the blades of the pruning tool with 70% alcohol solution.
- Wipe the blade with a paper towel or cloth to clean off any plant sap adhering to them.
- Spay the blade again with 70% alcohol solution and allow it to slowly evaporate.
Allow the alcohol solution to dry naturally, the time that its sits on the blade is the time that it is sterilizing it and killing pathogens.
Is Bleach Safe to Use on Pruning Tools?
Do not use bleach to sterilize pruning tools, as it corrodes metal, causing pitting and erosion, which damages the sharp edge of cutting tools and the surface finish of the blade.
Bleach solution is only suitable for sterilizing and disinfecting large hand tools such as garden forks, rakes, shovels and spades, when working with infected soils. It’s also used to disinfect pots that diseased plants were growing in.