📌 Quick Summary (TL;DR): Fighting Thrips on Stored & Green Onions
- 🌍 The Problem: Onion thrips (tiny, elongated black bugs) can survive the winter dormant in your stored onions. When you bring them out into the warmth or try to force them for fresh green onions (scallions), the thrips wake up and multiply.
- 🌿 Symptoms of Damage: If infested onions are planted for greens, the emerging foliage will look striped, deformed, and wrinkled (corrugated).
- 🛡️ Organic / Chemical-Free Solutions: Growers strongly advise against using synthetic pesticides if you plan to eat the green tops. Instead, they use old-school DIY methods:
- Hot Water Soak: Peel the onion down to the white layer and soak in hot water.
- The Alcohol Vapor Method: Place a heavily vodka-soaked cotton ball inside the onion storage crate, cover it with plastic wrap for 24 hours, and keep it in a cool place. The fumes kill the thrips.
- Sanitizing Soaks: Before planting, peel the bulbs and soak them in a sanitizing solution (like baking soda or potassium permanganate) for a few hours, agitating the water to drown the pests.
Luda, got another question for you. My stored onions started going bad, so I took a few sprouted ones and planted them in a container to grow some green onions (scallions). Well, I found little bugs on the greens, which I’m assuming are thrips. Started inspecting the main onion crate… and yep, those thrips are in there too, tiny long black bugs.
Is there any way to fight this? And where did they even come from? After the harvest, I peeled them all the way down to the clean white skin, and they sat in the crate all winter without a bug in sight… what a pain in the butt.
Russi: Is there any way to fight this? And where did they even come from?
Anya, I was peeling an onion today and oh my, there were so many of those critters crawling around. That kind of onion is bad news for growing greens too—the foliage will come out striped and corrugated/wrinkled. As for where they came from, they were most likely dormant and just woke up or multiplied.
You can peel them and soak them in hot water. I only have a few onions left in storage, so I’m not stressing too much. That’s actually why I wanted to plant my onion sets out in the greenhouse by the end of March.
Had to trim the green tops a bit today. But after this Sunday’s cold snap, I’m going to start prepping one of the greenhouses for early planting.
Russi: Is there any way to fight this? …what a pain in the butt.
I usually fight them with vodka 😁. I soak a cotton ball heavily, stick it inside the crate for 24 hours, and cover the whole thing with plastic wrap. The main thing is not to put the cotton directly on the onions, and don’t put the crate in a warm spot so you don’t build up too much moisture. Thrips die from the vodka fumes.
And before planting the sprouted onions for greens, I always soak them in a pale pink potassium permanganate solution for a few hours, aggressively swishing the bulbs around in the water with my hands. Hoping they drown 😄. You could obviously treat them with actual pesticides, but I don’t use chemicals on anything meant for fresh green onions.
📝 Editor’s Note for American Growers:
- Potassium Permanganate: In Eastern Europe, Potassium Permanganate (sold as purple crystals) is a staple household item used as a mild fungicide and pest soak for seeds and bulbs. Since it is highly regulated and hard to find in US/Canadian drugstores, American gardeners typically substitute this with a mild Hydrogen Peroxide soak (1 part 3% H2O2 to 4 parts water) or a quick dip in a Neem oil & Castile soap solution to kill off overwintering thrips before planting.
- The “Vodka” Trick: The evaporating alcohol fumes kill soft-bodied insects like thrips. If you don’t want to waste good drinking vodka, standard Isopropyl (rubbing) alcohol on a cotton ball works exactly the same way as a DIY fumigant!
Lyudmil, they are selling so many onions at the stores right now! Bought a bag on sale at Auchan. Thinking about sorting through them and planting the sprouted ones for green onions. But what should I do with the rest of them? The sprouting process has clearly started, they might all wake up and start growing!
Katya! Yes, you definitely need to sort through them. Separate the ones that won’t store well and plant them for greens. The rest should hold up for another month, I think. If anything, you can just plant them out in the greenhouse a little earlier.
It’s weird that they are selling them so cheap right now when demand is high—they probably stored them improperly.
Aleksan9ra: It’s weird that they are selling them so cheap right now when demand is high—they probably stored them improperly.
Yeah, you can see a lot of sprouted ones in the store. I picked a bag that had fewer sprouts, but there are still some dried-out ones with rot in there)
You could try soaking the onions in a baking soda solution (make sure to peel them down to the clean white layer first). That method always helps me when I’m forcing green onions indoors during the winter.
