Diatomaceous earth

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  • #51100


    Hello fellow monarch enthusiasts! I joined this site to ask for tips on growing swan plants. I am currently growing a load of them from seed over the winter so they will be a decent size when caterpillar season rolls around!

    At the moment I have thrips living on my plants. It’s not a severe infestation but I’d rather not have them at all. I refuse to use any pesticides for obvious reasons. Is it safe to use diatomaceous earth on swan plants that will later be food for monarch caterpillars? I don’t want to hurt the future caterpillars!

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  • #51112


    Hi Jacqui!

    Yes, I am certain they are thrips. I had aphids on my big plant in the garden and there’s no confusing the two. I don’t think it’s very common, it took quite a bit of searching to figure out they were thrips. I’m living in the Waikato, a little south of Hamilton.

    I’m growing my plants inside, it’s too cold for them outside, so I definitely won’t get any caterpillars yet! But unfortunately I think the warm, dry, predator-free environment of my living room is letting the thrips thrive. I’ll look into he Bioforce natural control. So far the thrips seem to be proving near-immortal, so I’m about willing to try anything (anything that won’t threaten the health of future caterpillars that is). I figured I could just wash the DE off the plants when it came to start housing caterpillars on them.

    Thanks for your help! I’m in the process of applying DE to the seedlings now, and I’ve set up a big rotating fan to blow on them. I read on here last night that that’s good for house-grown seedlings!



    I don’t think diatomaceous earth will affect your monarch caterpillars, Maphy.

    Are you sure they are thrips? I’ve never had thrips on my swan plants – aphids (oleander aphids, Aphis nerii) yes. But whereabouts are you?

    You are most unlikely to get caterpillars on your plants at this time of the year, so I think you’d be quite safe using d. earth – or better still, remove the leaves with the thrips on them and straight into a plastic bag and into the rubbish. You should be able to eradicate them that way.

    Also, I think Bioforce have a natural control to combat thrips.

    Good luck with it! Good work for getting your plants going early.

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