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With the harvest season upon us and wet weather approaching, AOA Code of Practice OliveCare® Administrator Peter McFarlane has provided a timely reminder about the bacterial Olive Knot Disease (Pseudomonas savastanoi pv. Savastanoi). A devastating scourge for Barnea and Frantoio varietals in particular, Olive Knot appears as rough galls or swellings on twigs, branches, trunks, roots, fruit or leaves. They grow rapidly into smooth, spherical green knots, increasing in size and becoming darker and more furrowed. Transmission is via the bacteria in the galls, which ooze out in wet weather and enter the tree through wounds, including those caused during harvesting. The only available control agent in Australia is Copper Oxychloride and Copper Hydroxide, which must be applied within 24 hours of adverse weather or pruning/harvest damage.
Olive Knot Disease management:
• maintain strong tree vigour to resist infection
• regularly monitor trees for symptoms
• prune and remove any ‘knots’ during dry weather periods
• disinfect pruning tools including chainsaws between trees; wash down and disinfect pruning and harvesting equipment before entry to and again after leaving the grove
• apply copper sprays within 24 hrs of rain, hail or frost events, after pruning and immediately post-harvest – timing is critical for effective control.
Growers experiencing Olive Knot Disease are requested to send details to McFarlane at: