16 November 2011

Gall Wasp

Everyone who has a lemon tree probably knows about the citrus gall wasp (Bruchophagus fellis)(EDIT - but this doesn't apply to Perth-ites.  Cane toads have reached WA, but not the gall wasp).   Although it's an Australian insect, it has only relatively recently moved south.  It apparently originated in in coastal Queensland and New South Wales, but it is certainly now prevalent in Melbourne.  It causes lumpy growths on the younger branches.  Apparently the wasp itself is only about 3mm long, and the adult lays eggs in young citrus growth in spring. The larvae hatch within three weeks and start feeding inside the stems, causing galls to form.   
The recommended way of controlling the gall wasp is to remove all the galls from the tree (and burn them, or throw them out in a plastic bag).    Our local nursery also suggests sticky insect catchers, in the hope that the wasps will be killed before they lay eggs,   I try and do both, but it's very hard to find and remove all the galls from a mature tree, and I suspect that the insect catchers are far from fully effective.  

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