Author Topic: Shallots pest puzzle  (Read 805 times)

Beersmith

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Shallots pest puzzle
« on: July 14, 2021, 20:57:22 »
I had an average crop of over wintered shallots.  Decent yield without being spectacular.

However I have observed an unusual pest that I cannot recall from earlier seasons.  Some of the shallots have a few small fairly thin black  things under the dry surface layers of skin.  They look like some type of larvae possibly thrips. They do not appear to have caused much damage so far. I have cut a few to investigate and cannot find any deeper in the body of the shallots.

My main concern is that the pests might mean the shallots do not store well which would be a pity as usually they are very long lasting if kept cool and dry with good ventilation.  Is this a well known pest?  Does anyone have expert knowledge about this?  Thanks!
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Shallots pest puzzle
« on: July 14, 2021, 20:57:22 »

saddad

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Re: Shallots pest puzzle
« Reply #1 on: July 15, 2021, 11:04:13 »
It sounds like the "new" leek moth... reddish/brown very small about 2-3mm long?

Obelixx

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Re: Shallots pest puzzle
« Reply #2 on: July 15, 2021, 15:22:51 »
The RHS has this info on leek moth but says the larvae are creamy coloured, not black.   See what you think.

https://www.rhs.org.uk/advice/profile?pid=652
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Beersmith

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Re: Shallots pest puzzle
« Reply #3 on: July 15, 2021, 16:09:33 »
It sounds like the "new" leek moth... reddish/brown very small about 2-3mm long?

Thank you both. I'm still researching, mostly on the web. Overall it perhaps seems closer to Allium leaf miner.  But I didn't see much damage to the leaves and no serious leaf distortion so I remain unsure. Also no evidence of damage to the bulbs themselves.

In retrospect I should have put them under a microscope. I have one of those cheap and cheerful electronic ones that connects to a PC through a USB.  Not the highest quality optics but pretty good for this sort of thing.

But I didn't do that. Worried they might not keep, I peeled them and prepped them for pickling. So I am now relying on memory. My bad.  I have another batch still in the ground.  I'll be watching those carefully. 
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Paulh

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Re: Shallots pest puzzle
« Reply #4 on: July 15, 2021, 19:54:50 »
It might be the pupae of the allium leaf miner- they are brown / black, but immobile rather than a live grub? They have two generations each year, one in about  March and another in about September and are actie on the plants for a few weeks before pupating.

Beersmith

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Re: Shallots pest puzzle
« Reply #5 on: July 15, 2021, 20:03:53 »
Pauly

Brilliant! You have it exactly correct.

 I have found a similar thing on the neck of a nearby onion.  I have placed it under my microscope and taken a photograph.  I'll post it soon. As you suggested it shows not the actual pest, neither grub nor adult but an empty pupa case.  So the adult has gone to continue its mischief on my maincrop onions and leeks.

 I know I may sound like a geek, but I find closely observing plants and insects endlessly interesting.
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Beersmith

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Re: Shallots pest puzzle
« Reply #6 on: July 15, 2021, 20:17:44 »
Apologies Paulh.

No familiarity intended.  Spell check altered your name.
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Beersmith

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Re: Shallots pest puzzle
« Reply #7 on: July 15, 2021, 21:48:12 »
And here it is
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Plot22

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Re: Shallots pest puzzle
« Reply #8 on: July 16, 2021, 07:00:07 »
It's Allium Leaf Miner. We get both Allium Leaf Miner and Leek Moth on our allotment site and have to cover all alliums under netting.  Last year leek Moth decimated anyone's leeks that were not covered. At the moment we are getting away with the Spring Onions but for how long I don't know.

saddad

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Re: Shallots pest puzzle
« Reply #9 on: July 20, 2021, 09:24:31 »
With Leaf Miner damage on Leeks if you get them late, say September, if you cut the green tops down to about an inch above the soil, and destroy the leaf with the grubs in, they grow back and you get a slightly later crop, and disrupt the life cycle too.