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Keeping it clean when pruning

Biosecurity

Coming to the end of harvest, and starting to think about pruning?  Have you considered how you and your contractors will disinfect pruning tools?

Key points

  • Pruning tools can spread pathogens that cause plant disease from a diseased tree to a healthy tree
  • When pruning, cut at least 20 cm below any visible symptoms in branches and stems
  • Disinfect pruning tools with disinfectant by spraying or dipping between cuts to help reduce the spread of plant diseases; at a minimum disinfect between blocks
  • Remove any diseased pruned material and fruit from the orchard
  • Sweep or mulch to remove infected pruning material and fruit
  • Implementing best practice in your orchard now will help you be better prepared in the event of a pest (biosecurity) incursion

Good hygiene is important to good orchard operations.

Why is cleaning pruning tools important?

Plant diseases, caused by pathogens such as bacteria, viruses and fungi, can be transferred to trees via soil and plant debris stuck on pruning tools, or from diseased trees to healthy trees if tools are not disinfected before cutting.  These plant disease-causing organisms may be present in the internal parts of the tree or on the bark surface and they can become attached to the pruning blades as they pass through the branch or shoot being cut.  A bit like if you are exposed to aerosols that transfer disease causing particles from one person to another. When the next cut is made with the contaminated blades, the pathogen may be transferred and a new infection established, spreading the disease through the orchard.

Organisms that cause disease are generally not visible to the eye, but the symptoms they cause may be.  This can be likened to a person being sick, but the organism that causes that illness is too small to see, or hidden inside that person. In plants the symptoms can include internal discolouration (often grey or brown) of stems and branches. Even where cuts are made below these visible internal symptoms, the pathogen may have grown beyond obviously diseased sections into what appear to be healthy plant tissues.

Disinfection of pruning tools, ideally between each cut, can help to reduce the unintended spread of plant diseases.  While it can seem cumbersome and impractical to handle disinfectants when making multiple cuts on the same tree or pruning many trees, it will reduce the spread of diseases that may otherwise become more difficult to control later if they become more established in the orchard. Would you apply a used band-aid to a cut on your finger?

A range of disinfectant products are available from horticultural suppliers.  Choose one that works well for your situation. Pruning tool blades can be dipped, wiped or sprayed with disinfectant solution before moving from one tree to the next.

Common options include 70% alcohol, rubbing alcohol (isopropyl alcohol) or methylated spirits.  Allow the alcohol solution to dry on the blade before making the next cut.  Other options include hydrogen peroxide and copper fungicides.  Bleach (sodium hypochlorite), while it is a reliable disinfectant when used correctly, is less desirable as it is corrosive to metal – and clothing.  Whatever you choose, be sure to read the product label and use accordingly.  The additional benefit is that cleaning plant residues and sap from pruning tools also extends the lifespan of the blades.

Other points to consider:

  • Remove any debris from tools prior to disinfecting; organic matter can reduce the efficacy of disinfectants
  • Disinfectants need to be used at the correct concentration and contact time to be effective
  • Disinfectants are inactivated by organic matter and fresh solutions need to be used each day
  • Alcohol is used at 70 percent because anything less than this is too weak to kill pathogens effectively. Pure alcohol (100%) evaporates too quickly so does not remain in contact with the pathogen for long enough to be effective. Keep solutions of 70-75 percent alcohol in a sealed container to prevent evaporation

Having simple best practice procedures in place in your orchard will reduce spread of diseases through your orchard, and also help to make sure you are prepared in the event of a pest incursion.

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