Wierd cigar growth form of Phragmites ?

During a recent wetland survey at Coolanillaun Bog at the southern end of Lough Corrib, an unusual growth form was noted on numerous Phragmites australis reeds. 

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The plants affected showed a deformed growth pattern and cigar shaped tips to the plants that tended to be shorter than surrounding 'normal' Phragmites plants.

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The cigars are in fact galls produced by infection of shoot by the fly Lipara lucens. The larva attacks the growing tip of the reed stem preventing the top internodes from elongating, which instead form a cigar-like swelling.

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Splitting open the cigars reveals the larva of the fly, one larva per cigar. 

© Peter Foss 2012