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I've sprayed my plants with DiPel DF as a way of controlling Tomato Hornworms. (The Dipel Solution called for 2 to 4 teaspoons per 32oz of water.) It killed the hornworms effectively; however, it's killing my plants too. I've tried to find them with a magnifying glass; I was able to find and remove a few, but there were more. They devoured a few of my plants and made a huge hole in 2 of my bell peppers. How can I eradicate the hornworms without hurting my plants?

Here are pictures of my plants after spraying them with the Bt solution a week later. Image2 image1 Image3

  • I don't know if it'll work, but applying sea minerals might make the plant less desirable for the caterpillars. It works for spider mites and a certain bad fungus on peppers, anyway. No guarantees. See store.rockdustlocal.com/Sea-Minerals-20-lbs_p_25.html – Brōtsyorfuzthrāx Dec 5 '15 at 20:23
  • I doubt the Dipel is responsible for the plant problems. It looks like your plants have Early Blight. Caterpillars can be hand picked, I've read that they will show up under a black light at night. I just check my plants at sunset for caterpillars if I see something has been munching. – Debbie M. Dec 5 '15 at 22:07
  • I've had no issue with my plants until I sprayed them with the Dipel. In fact, the other plants that I did not spray are still fine. It's the reason why I drew the conclusion. Earlier in the year, I had the same thing happened after spraying my plant with a Diple solution. – Josiane Ferice Dec 6 '15 at 0:53
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I can't offer suggestions on your sick tomatoes, but I can tell you what worked for me against hornworms. We are pesticide and insecticide free here (except natural ones).

In my quest to remove invasives from this property, I came across Japanese (Chinese) Lantern this spring. I pulled A LOT until I noticed something was eating its leaves. I left a small patch of the plants (in case it was a "good" something). Later in the summer, I noticed tomato hornworm larvae on them, but no tomato hornworms on the tomato plants in the garden about 100ft away. All but one of the Lantern hornworms I saw were parasitized by the Braconid wasp, too.

So, it seems that Chinese/Japanese Lantern is an excellent decoy plant for tomato hornworm, at least here in USDA 6b/7a. It's noted that it can be invasive (http://www.gardenersnet.com/flower/chineselanterns.htm) but it's easy to control by pulling & only leaving a few lanterns to sprout next year. Be sure to plant nectar plants for the adult wasp near your decoy patch http://www.agardenforthehouse.com/2011/08/when-not-to-kill-a-tomato-hornworm/).

If you want to attract black-swallowtail butterflies and protect your carrot crop too, plant Golden Alexander and let the Queen Anne's Lace have some space too.

HTH. If this is TMI, feel free to edit.

  • Physalis alkekengi is a perennial (even in quite cold areas). It spreads through rhizomes a lot more than through seeds. If yours isn't growing back every year and spreading without the need to reseed, it's possibly something like a Cape Gooseberry or other ground cherry instead (or even a tomatillo). It could just be another wild Physalis species, too (there are quite a few). This is what Physalis alkekengi looks like: rareseeds.com/chinese-lantern-gigantea The husks can be greener than that, too, I think. The berries turn red. The husks can turn skeletal. – Brōtsyorfuzthrāx Dec 8 '15 at 12:41

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