Witches brooming of garlic and Allium Leaf Miner #832120

Asked May 25, 2023, 10:42 PM EDT

I have grown garlic and onions in Howard County since 2017. It is becoming increasingly more difficult each year, and I have run into two primary problems, which I’m beginning to suspect are related, and I’m curious if you have any input. I first encountered Allium Leaf Miner in 2021. My onions were stunted badly, and I didn’t really know why until it was too late. The leaves were curled and distorted, and I did end up harvesting a crop of small but usable onions. The same year, I noticed that my garlic was “brooming”. Also called “witches brooming”, it’s when the developing cloves sprout prematurely, and send skinny leaves up through the main stalk. This causes the cloves to not develop fully and not store as well. I was doing some research online to find the cause of it, and I found a few Australian sources suggesting that it can be caused by excessive nitrogen in fall and winter, and/or fluctuating winter temperatures. However, 2021 was the first year I saw this phenomenon, which also happens to be the first year that allium leaf miner showed up in my garden. About 50% of my garlic plants are brooming this year, but some varieties are worse than others. I am wondering; could the stress from allium leaf miner could be causing the “brooming” in my garlic?

Howard County Maryland

Expert Response

Hi- witches broom is reported infrequently and when it appears it affects a small percentage of total plants. 

ALM has spread to 4 states since 2015 and there have been no reports correlating ALM and witches broom so we think that your issues are unrelated. We'll ask our commercial vegetable IPM specialist to see if he has seen any kind of association.
Thank you. I can tell you in my case the majority of my plants have been affected since 2021.

Sent from my iPhone

On May 26, 2023, at 10:06 AM, Ask Extension <<personal data hidden>> wrote:

The Question Asker Replied May 26, 2023, 4:30 PM EDT

This happens no matter who I get my seed garlic from. It also anecdotally seems to be happening to friends of mine in my area. Something else is causing it to be more frequent than before.

The Question Asker Replied May 28, 2023, 8:40 AM EDT

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