Pests and Diseases forum: Thrips on indoor seedlings

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Name: Danita
GA (Zone 7b)
Charter ATP Member Forum moderator Hummingbirder Salvias Butterflies Birds
Plant Identifier Vegetable Grower Container Gardener Seed Starter Cat Lover Region: Georgia
Apr 1, 2014 3:38 PM CST

I just discovered thrips on my indoor seedlings. I've never had them in the house before so I'm looking for tips on what to do. Should I toss the seedlings or put them outside and spray with Spinosad? We should be having a week of no temps under 40F.

It's mostly pepper seedlings (and a few flowers like Echinacea) so I won't be using systemics. The seedlings are still small, with only one or two sets of true leaves.

Thanks for any advice!
Name: ZenMan
rural Kansas (Zone 5b)
Kansas 5b
Annuals Butterflies Hummingbirder Region: United States of America Hybridizer Garden Photography
Garden Ideas: Level 2
Oct 14, 2014 6:33 PM CST
Hi Danita,

Well, rats! Nobody answered. Just out of curiosity, how did this turn out? Last Spring (it was probably in the March-April-May time frame), I had a disastrous outbreak of Western Flower Thrips (WFT) on my indoor zinnia seedlings. I had been relying on Imidacloprid systemic insecticide to protect my zinnia seedlings from whatever, but apparently the WFT became immune to it and killed about half of my zinnia seedlings before I took the rest outside on the deck and sprayed them with Acephate. Acephate smells very bad, so using it outdoors is preferable, if not an absolute necessity. It did kill the thrips almost instantly and I transplanted the seedlings into my garden, where they recovered from terrible damage and thrived.

I have consulted with an expert at Kansas State University, and he recommends I start with Spinosad as an initial indoor control. From my reading here and there on the Internet, it appears that WFT become resistant to Spinosad rather easily, so I am still looking for a more potent anti-thrips agent that I can use indoors on my zinnias. I grow zinnias indoors during the Winter (I am a zinnia hobbyist and amateur breeder) and have a couple of trays of zinnia seedlings up now, and potentially vulnerable to a thrips attack.


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