Onion thrips on leeks?

[beverleyParticipant]

HI,

I was looking forward to a spectacular crop of leeks to harvest gradually over the winter. However, on my first harvest, I discovered they were infested with numerous tiny light brown “things” about the size of a pin head. These are burrowed between the layers. On close inspection there are also some tiny whitish maggots.

The effect of these pests is to shred the leaves. Oddly enough, the leeks look healthy enough (at least in the initial stages – eventually the leeks topple over. So far this has only happened to the small size plants) and I only discover the infestation when starting to clean the leeks.

My web search suggest that these are onion thrips that are stimulated by long hot summers.

My question is, will these lodge in the soil and become a problem for future years?

Many thanks

[ElleGeeParticipant]

Could it be leek moth? I’m in France where the moth causes a great deal of damage similar to your description. There has been discussion about them on this forum, so clearly a problem in the UK too. No part of the lifecycle occurs in the soil. Local friends recommended alternating rows of carrots with leeks, but sadly, that did not help. I’ve found the only solution is to cover my leeks with mesh until the end of September.

[beverleyParticipant]

Hi Ellgee,

Many thanks for your reply which sent me to the RHS website to confirm. RHS say leek moth is very similar to allium leaf miner and on following up the description of that pest, I think that is likely what I have.

I found this picture of the pupae and it is these that are infesting my leeks https://www.gardenorganic.org.uk/news/take-part-our-allium-leaf-miner-survey

As with your moth, the control seems to be covering with fine mesh in March and in September October.

Thanks for you help in identifying these.

Best wishes
Beverley

[RhysParticipant]

Beverley

I have had this problem for three years and now I limit myself to growing Autumn Mammoth for harvest mid August to late September, after planting out in mid May.

It is not optimal but I am trying to break the cycle of reproduction by not having any alliums growing when the bug reproduces. So no garlic, plant out onions later and harvest leeks early.

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