Bt (Bacillus thuringiensis ) sold as Dipel, a dust or Thuricide, a liquid is the common standard treatment for hornworms - many many discussions about it here and on the web and yes it is approved for organic use.

Handpicking works very well IF you can monitor the plants daily. In your zone you will have at least 2 cycles of them a year and possible 3 depending on where in the zone you are located.

Dave

The Tomato Hornworm is a moth, so therefore nocturnal. You could check for eggs on the underside of leaves each morning, and also keep an eye out for the caterpillars, now that you know what they look like.

My experience is that once you find them and remove the offenders, they don't usually come back - unlike those dratted Cabbage White butterflies that never stop laying their eggs on brassicas!

Linda

My tomatoes were infested with them. I had to pick them off by hand. When I tilled I looked for their cocoons but I doubt I got all of them. Not sure about chemicals but did read it might help to introduce some parasitic wasps. I even tried to get birds interested in them but they wanted no part. They can do a number on a plant. Chemicals might be your best solution. Not sure if this is helpful or meaningful but they emerge from the ground and crawl up the plant so perhaps in the future early prevention is key? I am growing corn where the infestation was last year and I'm definitely going to use something on the young stalks to prevent them from crawling up.

William - hornworms don't go after corn. They are a tomato and pepper pest. And they emerge from their cocoons in the ground as moths which then lay eggs on the plant leaves and the caterpillars emerge from the eggs on the leaves.

BT as mentioned above is not a "chemical" but a naturally occurring bacteria and has repeatedly proven for decades to be an effective control for them.

Dave

Here is a link that might be useful: Tomato hornworm info and pictures

as dig said...picking works. If you are willing to hunt for them every few days...it might be the best solution (especially if you tend to shy from chemicals). Now that you are dialed-in to the problem...all will be good.

Oh that's good to know. The way they ate my tomatoes I was taking no chances. Besides there are grubs in the ground and wireworms.

My tomatoes are going in containers this year and I'm definitely going to watch them like a hawk.

I wonder if ducks would be able to spot and eat them?

Picking is the best way to get hornworms. If you look at your tomato stems a while, they suddenly become easier to see even when small.

If you spray the plant with water sometimes the hornworm moves and you can see it.

I would go with the Bt, which is organic. Spray it every few days. Otherwise, hornworms fluoresce a little under black light at night, so you can spot them with a UV flashlight if you get real close.

It also helps to try to eliminate the moths if they congregate around a light at night.

Try a bird bath in your garden. The birds are my gardens best defense against hornworms. Watching the birds fly out of the plants with hornworms in their mouths is a common site. As long as there is water for them they don't peck at my tomatoes.