One of the best ways to prevent the spread of fungus and other plant diseases is to prune out infected parts. However, once you make a cut in the diseased plant, fungus spores and other pathogens can cling to your cutters. Then, when you move on to prune a healthy plant you could end up transferring diseases via the infected shears.
So...what to do? We all know that nothing works like bleach in killing germs. But does it work just as well for disinfecting your garden tools?
In 1992, scientists at Kearney Agricultural Center in California's Central Valley tested various readily available and commonly recommended disinfectants. The products tested were:
o Chlorine bleach
o Hydrogen peroxide (3%)
o Listerine (at full strength)
o Lysol (regular, containing o‑phenyl‑phenol)
o Pine-Sol (19.9 percent pine oil)
o Rubbing alcohol (70% and above)
The scientists found that soaking or spraying pruning blades for a minute or longer in either a full-strength or a 1-to-5 solution of chlorine bleach, Lysol, or Pine-Sol brought the most consistent protection. Interestingly, just dipping the blade quickly often did not disinfect properly. Chlorine bleach generally did a better job for quick dips, although none of the disinfectants proved completely effective.
Since this study was done, more convenient disinfectant methods have emerged. For example, Clorox now sells disposable bleach-free disinfectant wipes in a pop-up container. These work great for cleaning jobs on smaller tools such as pruners, trowels and knives. Use as many wipes as it takes to completely remove all infected plant sap from tool surfaces and blades. Clorox claims the wipes can kill several types of bacteria in 30 seconds.
For larger tools (like shovels and shears) that have been in contact with an infected plant, use paper towels to remove all dirt and sap. Then soak the tool in a mix of 1 gallon water and 2 cups bleach for 10 minutes. Wipe the tool dry, and oil it promptly to discourage corrosion. Dilute the bleach water thoroughly before discarding.
Other options include keeping a small spray can of Lysol or a small bottle of rubbing alcohol or hydrogen peroxide in your gardening bucket with some clean old rags.
A couple of environmentally-friendly disinfectant products have recently entered the market. Some gardeners recommend Physan 20, a broad-spectrum fungicide and disinfectant. (Physan is toxic to fish, however, and should not be used for or near fish ponds.) You can read more about it at http://www.physan.com/.
The future of fungicide elimination may be in a product called Oxidate. Organic farmers have been saying great things about this hydrogen dioxide product, which kills bacteria, fungus, algae and their spores immediately on contact. It is currently recommended for use by commercial growers only. And, it's not cheap: 2-1/2 gallons will set you back around $140.
Whatever disinfectant method you choose, be sure to keep your tools clean and sharp. Lastly, if you don't regularly wear gardening gloves, be sure to wash your hands frequently when touching plants.