The first Tobacco Hornworm (caterpilar of Manduca sexta) on tomato plants for this year. Found it this morning, 21 Mai, 2014 :

Now, it requires daily inspection and collecting the caterpillars. A single caterpillar can ruin the entire plant. Better more inspections per day.
This

I collected it from a plant , today in late afternoon. It's more mature than the above. The colors are sharper and the horn has the characteristic red color. It is a little bigger too. (Still not very big, both have a little less of 2 inches. They can grow more.)

The green color gives to them an excellent camouflage and are relatively difficult to see.
If you see leaves or green fruit attacked / eaten, look for the caterpillar.
I think, this ear, they appeared earlier than last year. Not sure, but I remember than last year I start to have problems with them only in early June.

Hopefully up more north we are a few weeks away. But thanks for the heads up

We found one a couple weeks ago. Picked it off and threw it to the chickens who made short work of it!

Just read something interesting. Sacred datura is more attractive to hornworms than tomatoes. I guess if you can get it to bloom early it would be great. Not sure if sacred datura is the regular variety.

The hornworms always go after our Jimson Weed (Datura innoxia)

I am going to plant some!