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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

Josiane Ferice
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  • 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 http://store.rockdustlocal.com/Sea-Minerals-20-lbs_p_25.html – Brōtsyorfuzthrāx Dec 05 '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 05 '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 06 '15 at 00:53

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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.

GDD
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  • 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: http://www.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 08 '15 at 12:41