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Maggots on asparagus


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  • Maggots on asparagus

    It’s my first time growing asparagus and I planted 12 crowns several weeks ago. 5 of them have sent up a healthy-looking spear each, which are now about 15cm/6” tall. Wondering why I’d seen nothing from the other crowns I carefully dug down to discover several white maggots eating away at the newly emerging spear tips just as they come out of the crowns, which appears to be killing them off or very heavily stunting their growth so they are not breaking the surface of the soil. Having discovered this, I had a look at the crowns of the ‘healthy’ plants and also found a few maggots lurking around those - in one case eating into and hollowing out one of the established spears.

    The maggots are no bigger than 8mm long and appear to look and behave very much like cabbage root fly maggots. I have brassicas growing in close proximity and these have been heavily attacked by cabbage root fly this week. Does anyone have experience of cabbage root fly targeting asparagus, or is this something different? Any ideas for how I defend against them, whatever they are?

    The soil was quite damp as generous watering seemed to be doing a good job of waking the crowns up from their dormancy, but from what I’ve read this does also provide more favourable conditions for root maggots. With that in mind, I’ve very carefully excavated down around the crown of all 12 plants, blasted the old wet soil off with a jet of clean water from a squeezy bottle, and then filled in the hole with a handful of bone-dry spent compost, in the hopes that this will create a hostile environment for flies/maggots while allowing the asparagus to keep establishing with its deep roots still in moist soil. I also have a packet of ‘Nemasys’ fruit & veg nematodes arriving by post in the next few days - bought for the brassicas but now I’m inclined to use it on the asparagus too. Any thoughts on the steps I’ve taken, and any other advice or info would be most welcome. Thanks for taking the time to read! Photos attached...


  • #2
    No idea tbh.
    I've looked at this site but there's nothing very obvious.....

    maybe in a few days you'll see more obvious damage?
    "Nicos, Queen of Gooooogle" and... GYO's own Miss Marple


    • #3
      I looked up "stem maggots asparagus" and asparagus miner came up. They're the larvae of tiny flies which lay their eggs on the stems near the soil surface. Sounds like it's probably that.
      As far as I can find, your best bet is just to ignore it. There are no treatments available (pesticides don't really work as the larvae are protected inside the stem), and the stem often survives the damage unless there is an extreme infestation, and even if it doesn't the roots should grow more.

      Your dry compost solution won't help, though. The larvae live exclusively in the asparagus stems themselves, not the soil. If anything, you need to be keeping the plants well-watered (not to mention fed), as their best defence against this sort of damage is simply to grow out of it as fast as possible.


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