Necrosis of Lateral Tips in Blackberry Caused by Botrytis.

The pictures below are of a farm call this morning concerning die back of laterals of maybe less than 1% of the total on blackberry.  The symptoms occurred fairly evenly across the farm without regard to inside or outside of tunnels, organic or conventional.

As one can see from the second picture below, the die back does not advance that far down into the lateral, and since the apical dominance has been pushed down from the tip, often a new branch can be found at the lower limit of the necrosis.  It certainly does not threaten the rest of the plant.

The key to understanding this situation was the presence of conidial masses on the outside of some of the dead tissue (Pictures 3 and 4 below), and also an observation by the attendant pest control adviser that plants are quite wet in the morning from guttation from the leaves.  Lots of surface moisture + cool weather + soft, nitrogen rich tissue at the tip of the lateral = Botrytis problems. 

Disease infection is very infrequent, the plant is rapidly maturing and the weather is warming so it is not expected that this disease will advance much further and no action is recommended.  Hat tip to the grower and his pest control adviser on picking up on this.

Dieback on blackberry lateral.

Not too great photo of dieback peeled down to core. Notice how dieback has advanced and apparently stopped. New lateral forming at lower edge.

Photo of Botrytis conidial masses on outside of dead lateral tip.

Conidial masses of Botrytis on the outside of a dead lateral tip.

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