Allium Leaf Miner (Phytomyxa gymnostoma)

In July I harvested my shallots and in August my onions grown from sets. Both crops were pretty awful and I wonder if this a bad year for these crops.
Also for the first time ever my shallots have been infected with what appears to be a minute bug. It is about one eighth to a quarter of an inch long, the width if a piece of cotton and is underneath the outside skin. It is found anywhere on the bulb i.e. top middle or bottom.


I sent two of my shallots to the RHS Advisory Service and they have told me that they have been attacked by that the Allium Leaf-Mining Fly.
The bugs described earlier are the pupal stage of the allium leaf mining fly. They are likely to be the pupa of the first generation of larvae which will emerge as flies this year and lay another batch of eggs. These hatch and the larvae will feed during the autumn before pupating. The pupa from the autumn generation hatch in the spring.


As a precaution all Shallots & Onions have been moved to the Summerhouse and only selected Shallots for sowing next year have been kept in the shed.


Five Shallots which have the bug have been put into a jar covered with double muslin and secured with elastic bands. I want to see if any flies emerge and I do not want the jar to be airtight.
Let us see if the bug hatches - should be September sometime - watch this space.


More information is available in a RHS Leaflet but for copyright reasons I cannot publish the leaflet.  It is though available for view on the web site address below or there is a lot of information on “Google”.

http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=643

Gone are the days when Onions & Shallots were trouble free vegetables to grow.

                                                                                                                              Mike Snowdon

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