pests and windex??

April 7, 2010

Hi everyone,

I have small centipedes in my office plant: a huge peace lily that I have to water nearly every day or it dries out and falls over.

I've tried insecticidal soaps with no luck and I can't find anything that says it'll work. When I water the plant, all the critters come to the surface for some air. A friend of mine said to just spray them with windex when they pop up. How much will this hurt my plant?

I can't drown the critters in my office because of the huge tub I'd need to put the plant in. It just wouldn't work.

Any info? Suggestions? Etc?

Thanks so much,


Comments (16)

  • tapla

    It's prolly a good thing the friend didn't suggest a flame thrower ......

    Centipedes are carnivorous, so they won't hurt your plants. If you really must be rid of them, a little DE will make short work of them with no need to worry about toxicity issues?


  • meyermike_1micha

    Al hit it right on the target!


  • rhizo_1 (North AL) zone 7

    DE = Diatomaceous Earth. You'll find this product in the garden or pest control section of any nursery or even big box store. Be certain to purchase the product intended for critter control and not for pool filters. The label will likely say something like 'food grade' or 'horticultural grade'.

  • rhynno

    My folks had suggested DE actually. I don't know why I didn't listen to them :/ oops lol. Ty guys! I'm glad that I don't have to windex them. As much as I hate to cause a mass genocide in my office, I need to get rid of them before they start crawling around on the floor looking for more food. At that point my coworkers might just grab flamethrowers to use on me :/! Eep!

    Thanks again guys!


  • greenman28 NorCal 7b/8a

    Just out of curiousity...
    Are you sure that they are centipedes and not some other worm-shaped critter in the soil?


  • rhynno

    Good point. I'm not 100 percent sure. They are about an inch long, pale translucent colour, tons of legs, skinny, roll in a ball (not a pillbug) when wet or disturbed, crawl to the surface when the plant is soaked, they stick to the soil rather than climbing the plant, the plant's getting yellow splotches on the leaf margins and at times near the centre of the very large leaves. I hope to get to a garden centre tonight to buy some DE.

  • greenman28 NorCal 7b/8a

    Roll in a ball? Hmmm, perhaps a millipede?


  • rhizo_1 (North AL) zone 7

    Excellent call, Josh. You had your antennae up, didn't you? It's always a good idea to know with some certainty WHO the culprit is!

    This does indeed sound like one of the millipedes. Most millipedes are feeders of organic debris, but if a lot of them are confined to a container (inside an office, for example, lol) they may also resort to munching on tender root tips.

    DE will also work on the millipedes. Don't be stingy with it. Again, be sure that it is the right kind.

    Sounds like your peace lily needs some attention, by the way. Ever considered dividing it?

  • karyn1

    Rhizo what is the difference between horticultural grade DE and the stuff you use in a pool filter. I used to use the old DE when we had our pool filter changed but was told that it was a carcinogen so for the past several years I've been using horticultural grade DE but I was just wondering what the difference was, besides price? TIA

  • rhynno

    Hmm I should post a picture of my lily. I repotted it about three months ago into a slightly larger pot (it's now in a 12" pot). It has two clumps in the pot but it's a huge plant :/.Maybe I should have put some vermiculite in the soil?

    I went to buy some DE last night and the lady at the nursery gave me fungus gnat spray instead and said that it should kill the millipedes. That sounds kind of strange to me but I'll have to see if it works I guess :). I have fungus gnats at home and have never been able to get rid of them so it was about time to buy some spray anyway haha.

    Thanks guys! I'll post a pic of the lily tonight hopefully :).


  • rhizo_1 (North AL) zone 7

    karyn, pool filter DE has been treated with high temperatures, creating a very high percentage (60%-70%) of crystalline silica. This is what can cause silicosis (not cancer), a very serious disease of the lungs. Pool filter DE is also not effective in controlling insects.

    Horticultural grade or food grade DE has a very low percentage of crystalline silica, depending upon the manufacturer. Look for as less than 1% to 3%. Even at that, care must be taken to avoid breathing in the dust.

    DE should be used in moderation. It's a broad spectrum insecticide, meaning that it can harm any critter with a chitinous exoskeleton. We need to remember that there are a lot more beneficial insects out there than pests.

    rhynno, I can't think of any sprays that would be particularly helpful with fungus gnats. Your goal should be to get rid of the little larvae (from the eggs that the gnats deposit) that live in the potting soil. They thrive in a moist environment and can feed on the roots if their population is high. We often see a problem with fungus gnats if the potting soil is kept too wet, either from over watering or because of a medium that just won't drain properly.

    DE can help with fungus gnat larvae, too. Try allowing the containers to dry out. Some have had success by layering plain sand on the top of the soil, so that the gnats won't lay their eggs.

  • rhynno

    Hey Rhizo,

    Thanks for the info! I've tried sand over the soil but it never totally got rid of them in my exp and they came back. I tend to ignore my plants and let them dry out (except for things like gloxinias) yet these damn gnats are always here. I've tried sprays before but never had much luck. This is a new product so I hope that I get lucky and I can finally get rid of them. It looks different than the others; it left a crsyaline sheen over the soil for some reason :/. I also have a million yellow sticky traps all over the house filled with dead gnats.

    I've also switched to buying soil from a fantastic local nursery instead of buying the soil you can get from Walmart etc and just mixing in whatever I needed. I wonder if the soil was just re-infecting my collection over and over again :/.

    Thanks for the help! I'd be thrilled to finally get rid of all the critters in my plants!!

  • karyn1

    Rhizo thanks for the explanation. I've asked in the past but was never given a reason. I use DE for slug control.

    Bt can help with fungus gnat larva and the yellow sticky paper reduces the adult population. It's not terribly attractive, especially when covered with gnats, but it works.

  • rhizo_1 (North AL) zone 7

    Sounds like you may need to resort to a biological control product we often recommend for a bad fungus gnat infestation. You need to look for Bt-I (Bacillus thuringiensis-Isralensis), a naturally occurring bacterial strain that infects the larvae of certain insects, including mosquitoes and fungus gnats.

    You can find Gnatrol (one brand name) in some good garden centers and on-line. But you can also look for those 'mosquito dunks' that are sold very commonly to toss into pools, ponds, and other standing water to get rid of mosquito larvae. Break up one of the dunks and soak a piece piece in your watering container for a few hours. Use that water when you water your plants as usual. (In other words, don't water more than usual.) You'll need to make several applications.

    If you have lots of plants, it will probably be well worth it to purchase the Gnatrol.

    If you do something as simple as adding plenty of perlite to your store-bought potting soil, you can decrease its attractiveness to fungus gnats. The coarser the mix, the faster it drains, the less you will be troubled by these insects. I've never seen a store-bought potting medium that suited me without a lot of amending!

  • taz6122

    I have to agree about the potting medium. I used mostly MG potting soil last year and had millions on fungus gnats and some problems with rot. This year I have mixed the soil with perlite and sand and have virtually no gnats and no problems with rot.

  • karyn1

    A mosquito dunk can last for quite a while. I reuse the piece of a dunk in jugs and tubs and just refill with water. You can't use insecticides with the Bt as it will kill it. It does take several applications but I find it's much quicker if the Bt is used in conjunction with the sticky paper.

    I usually ammend my potting mixes depending on what I'm planting but have found a few brands that are quite good straight from the bag, Fafard 3B, Happy Frog and Foxfarm Ocean Forest.

Need help with an existing Houzz order? Call 1-800-368-4268