Thursday, December 8, 2011

EL 32 Bunch Closure

Light Brown Apple Moth damage to grapevines before bunch closure.

Bunch closure (EL 32) in tight bunched varieties is a critical time in the lifecycle of botrytis. The greater the amount of ‘trash’ or damaged berries from light brown apple moth (above) at bunch closure the greater the risk of botrytis.

Botrytis first infects berries as latent or ‘unseen’ infection, during flowering when the flower cap falls. A second type of infection begins to develop as berries press together. Botrytis fungal threads (mycelia) begin to grow from fungus on dead and dying plant tissues (such as ‘trash’ flower debris or damaged berries). This growth from dead material infects berries after berry softening and progressively increases in wet or humid weather.

Alternatively varieties grown with an open bunch configuration develop less rot in wet conditions. They have better airflow and lower canopy humidity after rain. A good canopy structure is a key part in botrytis control. High quality Shiraz that is picked in early March has a low risk of developing a significant level of botrytis before it is picked - without chemical application!

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