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Allium Leafminer -- pest of onions, garlic, chives, leeks

This discussion was started in another thread -- I'm copying them to continue :wink:

applestar wrote:.....
In my garden I'm currently having problems with onion maggots. I had them seriously affect my onion harvest last year -- I was able to salvage the harvest but had to chop and freeze or dehydrate rather than curing and storing whole.

I found them infesting the overwintering Egyptian walking onions and some of the garlic -- fortunately not in the main garlic bed but scattered "volunteers" which are garlic that I failed to harvest for one reason or another last year. I'm afraid to find out if they are in the main garlic bed, and am very concerned about the onions as planted this year.

Onion magggot flies apparently overwinter as pupae.
pepperhead212 wrote:Apple,

Another pest that just showed up in our area in 2015, brought in from another country, is the Allium Leafminer (ALM). Your description of the onion maggot reminded me of this. A few gardeners in SE PA as well as MD on another forum had their garlic and onion crops destroyed by the ALM last season; I had no signs of it, but I took prophylactic measures. this year, and covered my garlic and chives, as I do peppers, to prevent pepper maggots. Here is a link: ... -leafminer
Thanks pepperhead212 -- Ugh! The photos and descriptions at the Penn State U. Extension site match what I've been finding. I even remember seeing that orange, tiny-headed fly (and asking it what kind of fly it was because I didn't recognize it). I was able to salvage those immature garlic by peeling the outer layers -- what would become the "paper" -- the inner undivided-into-cloves bulb wasn't affected.

It looks like I will be digging up what seemed like prematurely yellowing Tzan Turban garlic as soon as it is light, and test digging one or two of the other varieties as well. I wonder if softneck Tzan Turban vs. the others which are hardneck may have made a difference because the other garlic are not collapsing.

As luck would have it, I planted some of my onions under insect barrier covers to protect brassicas and Asian greens from cabbage white and I planted the onions with them, but others planted in the may not avoid the ALM.... Hm... I have extra onion sets I never got around to planting... I wonder if it would help to plant now ("after May").

I was thinking that I may have to pull all of my Egyptian onions, including the mother clumps, and seriously consider giving up on growing garlic this fall and onions next year even before finding out about this Allium Leafminer. Kind of bumming right now to read all that, but maybe there is a way -- perhaps beneficial nematodes this fall? (Unfortunately, I think I might have missed the window for applying in spring, though if this cooler spell continues into June, I might still have a chance).

Super Green Thumb
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Both of these pests are similar, in that flies lay eggs, then the larvae burrow into the plant - much like SVB - making it next to impossible to control, other than covering them. And if any were in the area covered, they could have pupated, thus they could come out under the cover, making it useless.

After hearing about all of these problems with ALM, I went around with a natural weed killer - Weedzap - and zapped all of those patches of garlic chives I had, and a few wild onion grass patches, then went around in late fall, and zapped any that had come back in the least. Then, this spring there were only 4 small, sickly looking patches, and I zapped those, so there are no plants that those pests can multiply on, at least nearby. And I made a long hoophouse for my garlic, shallots, and chives, and have them all covered.

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Location: Hawaii, zone 12a 587 ft elev.

I get onion maggots just about every year in the green onions. They are more of a nuisance than anything else. Even the commercial farms have them. I can tell because when the onion maggots attack their crops, they usually cut off the tips of the green onions in the market. The damage is mostly cosmetic but does not make the onions unusable. They are a seasonal problem and after a while they go away.

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