As the season wraps up and tools and equipment are stored away for the season be sure to clean tools properly to prevent plant pathogens from surviving from one season to the next.
Plant pathogens have multiple strategies for survival. Many common plant pathogens survive in infected plant debris and soil. As a result, crop rotation and proper disposal of crop residue play an important role in reducing disease problems from year to year. But what about the large equipment, hand tools, wires, stakes, high tunnel plastic, clips, and other day to day objects that are used throughout the production season?
• 10% solution of chlorox (5.25% sodium hypochlorite)
• 20% solution (weight to volume) of nonfat dry milk
• 2% solution of Virkon S (20.4% potassium peroxymonosulfate and 1.5% sodium chloride)
• undiluted Lysol (.1% alkyl dimethylbenzyl ammonium saccharinate)
No other disinfectants in the study effectively removed all of the viruses from the cutting tools.
• Virkon S (20.4% potassium peroxymonosulfate and 1.5% sodium chloride) a 2% solution
• Green-Shield (10% n-Alkyldimethyl benyl ammonium chloride and 10% n-Alkyl dimethylethyl benzyl ammonium chloride) at 1 tsp/qt
• Des-O Germ 100 (Poly& hexamethylenebuguanide and benzalkonium chloride) at 100ml/100L
• Menno Florades (9% benzoic acid) a 3% solution
• Menno-Ter forte (Didecyl dimethyl ammonium chloride) a 1% solution
• Chlorox (5.25% sodium hypochlorite) a 10% solution
• Kleen Grow (Didecyl dimethyl anmmonium chloride 7.5%) at 4 ml/L
• BioSide (Peroxyacetic acid 15%; hydrogen peroxide 22%) at 1 oz/10 gal
• Sanidate (Hydrogen peroxide 23%; peroxyacetic acid 5.3%) did not clean the fungal plant pathogen from the cutting tool and required 1 minute of treatment to remove the bacterial plant pathogen.
• StorOx (27% hydrogen dioxide) was not effective with a 1 second treatment but removed both the fungal and bacterial plant pathogen after 1 minute.
• None of the three OMRI certified disinfectants were effective against the viral plant pathogens in this study.
• 10% bleach (5.25% Sodium hypochlorite), which is allowed as an equipment cleaner in organic production, removed bacterial, fungal, and viral pathogens tested in the study.
What about rubbing alcohol?
Although the OSU study did not test rubbing alcohol as a disinfectant, an older study tested 3 concentrations of rubbing alcohol (70%, 90%, and 99% isopropyl alcohol) for its ability to remove the bacteria that cause fire blight from a pruning tool. In the study, researchers cut through a fire blight infected apple, then soaked the tool in isopropyl alcohol for 1, 3, and 5 minutes, then used the tool to cut into a healthy apple. In all cases, the cutting tool spread the fireblight bacteria to 25% of the healthy apples. This shows that rubbing alcohol was not an effective disinfectant for bacterial diseases.
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| Soil covered tools, ready to be cleaned and disinfected M. Grabowski, UMN Extension |
Plant pathogens have multiple strategies for survival. Many common plant pathogens survive in infected plant debris and soil. As a result, crop rotation and proper disposal of crop residue play an important role in reducing disease problems from year to year. But what about the large equipment, hand tools, wires, stakes, high tunnel plastic, clips, and other day to day objects that are used throughout the production season?
Can plant pathogens survive on tools and equipment?
Some viruses like Tomato Mosaic Virus, Tobacco Mosaic Virus, and Pepper Mild Mottle Virus are very durable and can survive on the surface of tools, greenhouse plastic, pots, and other equipment that comes in contact with infected plants. Fusarium wilt of cucumber and tomato and Fusarium stem and crown rot can be moved as spores on shoes, packing crates, and tools, and remain on greenhouse benches and structures. Bacterial canker of tomato can survive on wooden stakes.Science behind choosing a disinfectant
Two recent studies by Dr. Miller’s lab group at Ohio State University tested 16 common disinfectants for their ability to eliminate plant pathogens on cutting tools used on infected tomato plants. The study cut into tomato plants infected bacterial canker (bacterial pathogen), gray mold (fungal pathogen), Pepino mosaic virus, Tomato Mosaic virus, or potato spindle tuber viroid (viruses). The researchers then exposed the tool to one of 16 different disinfectants for 1 second or 1 minute. The tool was then used on a healthy plant, which was monitored for disease. The results provide useful information to help select a disinfectant. |
| Tobacco mosaic virus on tomato M. Grabowski, UMN Extension |
Viruses
The following disinfectants completely cleaned the cutting tools of all three viruses in the study.• 10% solution of chlorox (5.25% sodium hypochlorite)
• 20% solution (weight to volume) of nonfat dry milk
• 2% solution of Virkon S (20.4% potassium peroxymonosulfate and 1.5% sodium chloride)
• undiluted Lysol (.1% alkyl dimethylbenzyl ammonium saccharinate)
No other disinfectants in the study effectively removed all of the viruses from the cutting tools.
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| Gray mold on high tunnel tomato M. Grabowski, UMN Extension |
Fungi and Bacteria
The most effective disinfectants in the study removed both the fungal and bacterial pathogen after just 1 second and include:• Virkon S (20.4% potassium peroxymonosulfate and 1.5% sodium chloride) a 2% solution
• Green-Shield (10% n-Alkyldimethyl benyl ammonium chloride and 10% n-Alkyl dimethylethyl benzyl ammonium chloride) at 1 tsp/qt
• Des-O Germ 100 (Poly& hexamethylenebuguanide and benzalkonium chloride) at 100ml/100L
• Menno Florades (9% benzoic acid) a 3% solution
• Menno-Ter forte (Didecyl dimethyl ammonium chloride) a 1% solution
• Chlorox (5.25% sodium hypochlorite) a 10% solution
• Kleen Grow (Didecyl dimethyl anmmonium chloride 7.5%) at 4 ml/L
• BioSide (Peroxyacetic acid 15%; hydrogen peroxide 22%) at 1 oz/10 gal
OMRI Certified disinfectants
• BioSide (Peroxyacetic acid 15%; hydrogen peroxide 22%) effectively cleaned tools of both the fungal and bacterial plant pathogen after 1 second.• Sanidate (Hydrogen peroxide 23%; peroxyacetic acid 5.3%) did not clean the fungal plant pathogen from the cutting tool and required 1 minute of treatment to remove the bacterial plant pathogen.
• StorOx (27% hydrogen dioxide) was not effective with a 1 second treatment but removed both the fungal and bacterial plant pathogen after 1 minute.
• None of the three OMRI certified disinfectants were effective against the viral plant pathogens in this study.
• 10% bleach (5.25% Sodium hypochlorite), which is allowed as an equipment cleaner in organic production, removed bacterial, fungal, and viral pathogens tested in the study.
What about rubbing alcohol?
Although the OSU study did not test rubbing alcohol as a disinfectant, an older study tested 3 concentrations of rubbing alcohol (70%, 90%, and 99% isopropyl alcohol) for its ability to remove the bacteria that cause fire blight from a pruning tool. In the study, researchers cut through a fire blight infected apple, then soaked the tool in isopropyl alcohol for 1, 3, and 5 minutes, then used the tool to cut into a healthy apple. In all cases, the cutting tool spread the fireblight bacteria to 25% of the healthy apples. This shows that rubbing alcohol was not an effective disinfectant for bacterial diseases.
Steps to Successfully Disinfecting Tools, Equipment, and Tunnels
- Remove all soil and plant debris attached to the equipment. Hard surfaces can be power washed to completely remove any organic material. Most plant pathogens survive best when sheltered by soil or plant material. It is harder for pathogens to survive on an exposed metal or plastic surface. This step also exposes the surface of the equipment so that good contact occurs between the disinfectant and the tool.
Old roots and soil on a used pot need to be removed before disinfecting the pot.
M. Grabowski, UMN Extension - Choose a disinfectant that will be effective against the pathogens that are common in your production system.
- Read the label of the disinfectant carefully and follow all label instructions. Disinfectants are legally pesticides and all pesticide laws apply when using a disinfectant.
Large tubs can be useful for disinfecting multiple stakes at once.
M. Grabowski, UMN Extension - Apply the disinfectant to completely coat the surface of the equipment. Be sure to get the disinfectant into corners and tight spaces.
- Small clips or wires are be most easily treated by soaking in a bucket of disinfectant.
- Wooden or bamboo stakes benefit from soaking in a large tub filled with the disinfectant to allow time for the solution to move into small pores and cracks common in natural materials.
- Large equipment like tractor attachments can be sprayed. Use of a pressurized sprayer with a wand attachment can be useful in reaching the top of tall equipment or getting into tight spaces like the tines of a tiller.
- The label instructions will indicate if a rinse with clean water is necessary. Allow tools and equipment to dry completely before storing.
