Dr Jenny Jobling

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VG05034 Managing Mildews - prevention using
systemic acquired resistance (SAR) in greenhouse
grown cucurbits.

• Dr Jenny Jobling
• Applied Horticultural Research and Adjunct
• Associate Professor University of Sydney

Dr Anowarul Bokshi
Mr Haissam Hamed
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What is Systemic Acquired Resistance (SAR)?

• It is a "whole-plant" resistance response that
  occurs following an earlier localized exposure to
  a pathogen.
• SAR is similar to the immune system response
  found in animals.
• SAR is associated with the induction of a wide
  range of genes (so called PR or
  "pathogenesis-related" genes), and the activation
  of SAR requires the accumulation of endogenous
  salicylic acid (SA).

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Systemic Acquired Resistance in Plants
Applied chemicals can also induce the plant to
switch on its defences

• Natural defences
• Physical barriers eg. lignin
• Chemical/toxic barriers eg. Chitinase enzymes
  phenolic compounds

Eg. Bion, Rezist
Pathogen attacks leaf
Signal from infected leaf induces remaining parts
of plant to switch on defences
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Chemicals used in the Trials

• Bion (Syngenta) 500g/L acibenzolar-s-methyl,
  registered for use to control Fusarium Wilt and
  Black Rot in Cotton in Australia and the USA
• Rezist(Stoller) A patented combination of
  micronutrients and polyamines registered in the
  USA for a range of horticultural crops
• Milsana (Colin Campbell Chemicals) The
  formulation contains 5 by weight of Reynoutria
  sachalinesis (Giant Knotweed) extract with about
  86 Basfoliar or equivalent liquid foliar
  fertilizer. Used in India and the USA.

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Key Experimental Results

• Bion, Rezist and Milsansa reduced the
  severity of powdery mildew
• In this experiment the fungicide Amistar
  did not

Bion vs Untreated
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Evidence for the Induction of SAR Chitinase
Activity Phenolic compounds

• Bion and Rezist induce phenolic
  compounds to restrict mycelial growth
• Milsana also stops growth but how?

• Bion induced the greatest enzyme activity
• After one application this was maintained
  for 28 days (4 weeks)

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Results when applied in Combination
BUT Total fruit numbers were less with Bion
Bion treatment Best plant health and crop yield
was with Milsana Bion in rotation Fungicide
was Triad 125
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In summary

• Bion provided consistent and long lasting
  control of powdery mildew in greenhouse grown
  cucumbers
• Bion or Rezist applied 3 times during the crops
  life affected plant growth (reduced yields)
• Best result was a rotational spray program with
  Milsana and Bion
• For best results plants must be healthy and not
  under water, climatic or nutrient stress
• Minor Use Permits would be required to use this
  strategy in Australian vegetable production