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Insects in dahlia stem

Sue & MuttonSue & Mutton Posts: 125
in Problem solving


Hi, only just got round to loading this pic up.  Any idea what these are and what I can do about them please? Every year some of my dahlia stems go black/mushy and these are inside. I always cut it down beyond the affected area and it's fine. Any ideas?

Posts

  • BobTheGardenerBobTheGardener Posts: 11,385
    I suspect they are grubs of some species of fly which was attracted to the decaying stem and laid eggs there.  The grubs will almost certainly be feeding on the decayed wet tissue and are unlikely to travel into the live material below, unless the rot itself is also progressing down.  I haven't heard of any specific insect which lays eggs in live dahlia stems, so don't think this is anything to worry about. :)
    A trowel in the hand is worth a thousand lost under a bush.
  • Sue & MuttonSue & Mutton Posts: 125
    Hi Bob, thanks for your reply. It's hard to know which comes first - the blackening and die back or the larvae. I'll keep you posted next year.
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