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daninthedirt

cutworms and diatomaceous earth

I had regular problems with cutworms and seedlings. That is, until I dusted the ground around them with Sevin. That worked a treat. But in the interest of minimizing use of such insecticides, this year I tried dusting the area around some basil seedlings with diatomaceous earth, which I like very much for other insecticidal purposes. I had heard that it worked on cutworms. But I was somewhat startled that it didn't. The effect of the DE on the cutworms in my bed was pretty much like it simply wasn't there. I quickly put Sevin around the undamaged ones. Does anyone have any real success with diatomaceous earth for this purpose? If you do, how do you apply it to make it work? Maybe I have to heap big piles of the stuff? As in, making a physical barrier out of it? Maybe the cutworms slither through the stuff, chop down a plant, and then go off and die somewhere?

Comments (21)

  • Nitsua
    9 years ago

    You might be right. The DE damages the worms but they still have time to chomp on your plants. After all, those tasty plants are 'to die for'.

    Supposedly, putting a collar of sticky molasses around the plants can deter them. Also, BT (Bacillus thuringiensis) is said to be quite effective.

  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    Original Author
    9 years ago

    Of course, when I put down Sevin, I don't believe I usually find dead cutworms laying on the dust. So I have to assume that they lose their appetite, and then go off and die somewhere.


  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    Original Author
    9 years ago

    Yep, I do that too. Though when you have a long row of peas and beans, that's a LOT of toilet paper tubes!


  • tishtoshnm Zone 6/NM
    9 years ago

    For peas or beans, I would use popsicle sticks on both sides of the plant, it would be easier than toilet paper tubes. That would be a lot of sticks still but they often last more than one season. Another option would be bamboo skewers that you could cut in half.

  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    Original Author
    9 years ago

    Um, I just planted about a hundred pea seeds. You want me to put popsicle sticks on both sides of each plant? C'mon. Now, for fewer plants, no, it takes me a few seconds to put cardboard tubing around each plant. It would take a lot more time juggling popsicle sticks. And how are popsicle sticks supposed to repel cutworms? Sorry, I just don't get that one.


  • zzackey
    9 years ago

    I never had cutworms attack my peas. Of course the cardboard tube method is just for a few plants.

  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    Original Author
    9 years ago

    Yep, cutworms will decimate my peas. I guess if you have cutworms that don't like peas, that could simplify things a little.


  • tishtoshnm Zone 6/NM
    9 years ago

    The popsicle sticks prevent them from wrapping themselves around the plant and cutting through the stalk. I have heard that cornmeal is supposed to help as well. The thought is that they gorge on the cornmeal and cannot digest it and then die. I have not tried. I had one really, really bad year of cutworms but they have not been as bad the past few years.

  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    Original Author
    9 years ago

    Really? I didn't know that was how cutworms did their damage, but on researching a bit, I see that you're exactly right. They have to wrap themselves around the stalk entirely to decapitate it. So at least I now understand how the popsicle sticks would work. Interesting. Learn something new every day. Thanks! I have to wonder if toothpicks would work as well. Those would do less damage to the roots underneath when you stick them in. But maybe the worms could still encircle the stem.

    Now, I still think that doing them for a whole row of seedlings would be impractical, but that's a nice strategy for protecting small numbers of seedlings. In fact, I'm just putting out a half-dozen canteloupe seedlings tomorrow, and I may try this. (I have *lots* of popsicle sticks!)


  • beesneeds
    9 years ago

    If you eat eggs and save the shells, try using crushed eggshells around your plants. Cutworms are supposed to dislike that as much as slugs don't like eggshells.

  • vgkg Z-7 Va
    9 years ago

    I've used toothpics in the past and they did work ok. Place 2 TPs right next to the plant's main shoot. Nails also work, but toothpics biodegrade if you forget about them.

  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    Original Author
    9 years ago

    As to eggshells, it's pretty much the same stuff as diatomaceous earth, so I suspect it wouldn't work here.


  • carolb_w_fl_coastal_9b
    9 years ago

    I also have used toothpicks like vgkg, but 3 instead of 2. For masses of pea shoots, I can see that being rather labor-intensive, but it is pretty quick work, regardless. They need to be right up against the stem. I don't have a prob w/ cutworms & peas, tho - the enemy here is slugs/snails. I sprinkle iron phosphate snail/slug killer pellets around just about everything I direct sow & that seems to prevent the pests from mowing down the emerging seedlings.

    This should easy to look up, but I don't think crushed eggshells & DE function in the same way; altho both are calcium carbonate, isn't the shape different on a microscopic level?

  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    Original Author
    9 years ago

    Yes, the shape on a microscopic level of DE and eggshells is different, but that of DE is destructive to most insects. Not sure how eggshells could be *more* destructive. Nice idea about toothpicks. Again, I'd feel better about shoving toothpicks into the soil right next to the stem because I have to believe that popsicle sticks would be more likely to shave off roots.


  • woohooman San Diego CA zone 10a
    9 years ago

    I'm a toothpick man. Been putting 2-3 up next to the stalk of all my transplants for a good ten years and haven't lost ONE seedling to cutworms since.

    Like others, I don't have a problem with cutworms on my snow peas.

    Note: I could see DE working on grubs in maybe a compost pile since it's usually a drier environment than a moist garden.

    Kevin


  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    Original Author
    9 years ago

    I like toothpicks. I put my melons in today, but didn't have many toothpicks. Used cardboard collars and Sevin. But I'll try toothpicks on my squash next week.

    As to my original question, is there no one out there willing to vouch for DE preventing cutworm damage? If so, how to make it work? I'm sensing an "old wives tale" here. DE is nice stuff, but next thing we'll hear is that it cures cancer and old age.


  • carolb_w_fl_coastal_9b
    9 years ago

    It might work if you could dust it directly onto the cutworms...

  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    Original Author
    9 years ago

    By the same token, I'll bet if I dropped a 10lb sack of DE on a cutworm, it would kill it.


  • vgkg Z-7 Va
    9 years ago

    Cutworms do their total damage very quickly on baby plants and as Nitsua above mentioned DE works slowly via death of 1,000 cuts. By the time a cutworm dies from DE the damage has already been done. DE is best for killing insects that destroy adult plants more slowly such as sucking insects.

  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    Original Author
    9 years ago

    Yes, by that measure, DE might well be helpful in general control of cutworms. But it is uneffective for protection of specific seedlings. The lore is that it is good for the latter. It is said that a ring of DE is a barrier that cutworms won't cross. I think that is simply untrue. They'll cross it once, but maybe not twice. So the best way to apply it for general control is not as a barrier, but spread uniformly over the bed, ideally well before the seedlings are there.

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