Ask a Question forum: Preventing and controlling Thrips on indoor plants

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Name: ZenMan
rural Kansas (Zone 5b)
Kansas 5b
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Sep 3, 2014 10:58 AM CST

One of my hobbies is growing and breeding zinnias, which I have done for the last few years. I grow zinnias in the usual outdoor settings, but I also grow some "breeder" zinnias indoors during the late Fall, Winter, and early Spring. Zinnias are not houseplants, and growing them indoors presents a number of problems.

In the absence of normal outdoor enemies, Thrips can have a population explosion on indoor zinnias (and other indoor plants). Last Winter I fought an on-going battle with Thrips, which ended in a tie. I "controlled" a lot of Thrips and grew many breeder zinnias to seed production, but the Thrips developed an immunity to the Imidacloprid systemic insecticide I was using, and I had to move the third generation seedlings outside to spray them with Acephate, because the Thrips were killing them. I did spray some inside zinnia blooms with Acephate to kill the Thrips that infested the many crevices of the zinnia blooms, but commercial Acephate smells very bad and isn't suitable indoors for that reason. (The smell may actually be a contaminate, because a Google search turned up one foreign company that was offering to produce odorless Acephate, but as far as I know, no such product is available.)

So I am searching for a suitable systemic insecticide to control Thrips indoors on my zinnias. At this time last year I thought it was Imidacloprid, but it isn't. Incidentally, I believe the specific enemy was the Western Flower Thrips (Frankliniella occidentalis).

Thank you,


Name: Anne
Summerville, SC (Zone 8a)
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Sep 3, 2014 1:11 PM CST
Your best bet is to dust your plants top and bottom with diatomaceous earth and on top of the soil. Totally inorganic with no smell.
"The Universe speaks in many languages, but only one voice. It speaks in the language of hope; It speaks in the language of trust; It speaks in the language of strength, and the language of compassion. It is the language of the heart and the language of the soul. But always, it is the same voice. It is the voice of our ancestors, speaking through us, And the voice of our inheritors, waiting to be born. It is the small, still voice that says: We are one. No matter the blood; No matter the skin; No matter the world; No matter the star; We are one. No matter the pain; No matter the darkness; No matter the loss; No matter the fear; We are one. Here, gathered together in common cause. we agree to recognize this singular truth, and this singular rule: That we must be kind to one another, because each voice enriches us and ennobles us, and each voice lost diminishes us. We are the voice of the Universe, the soul of creation, the fire that will light the way to a better future. We are one."

Name: Elaine
Sarasota, Fl
The one constant in life is change
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Sep 3, 2014 1:48 PM CST
You're seeing the same phenomenon that the medical community has with antibiotics. Thrips are going to develop immunity to any systemic eventually. The more effective methods are the old-fashioned mechanical ones like soaps and oils, jmho.

I've been fighting a similar battle with spider mites on brugmansia the last few years, and my neighbor finally convinced me. He was caring for my brugs while I was away on a trip, and they were looking pretty sketchy when I left. Ten days later when I returned, they had rebounded amazingly. When I asked him what he did, he said he just gave them two really thorough baths with soapy water using a 2-gallon sprayer.

Btw, that same neighbor has his Masters in Hort from UF and worked as a pesticide inspector for the State of Florida for some years.

Cross posted with Anne, and yes, DE is another great 'mechanical' solution. Especially good for indoors because of no smell, and also not impacting beneficial insects as it can outdoors.

"Success is stumbling from failure to failure with no loss of enthusiasm." –Winston Churchill
[Last edited by dyzzypyxxy - Sep 3, 2014 1:51 PM (+)]
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Name: Sandra Taylor
Cleburne,texas (Zone 7b)
Oct 27, 2014 11:15 PM CST

This grew volunteer if i had planted it might have died. I have no idea what it is but beautiful and oh so cheery to.

Name: Suzanne/Sue
Sebastopol, CA (Zone 9a)
Sunset Zone 15
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Oct 28, 2014 12:45 AM CST


@Shtaylor44 it looks like you may have posted in the wrong thread?
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