Looks like one of those hungry little buggers.

Tomato fruitworm.

Nasty buggers. They're the same as corn earworm, and I have a problem with that too. I just hate how messy they are.

Try dusting the plants, particularly the tops of the fruit, with Bt (Bacillus thuringiensis); it's a bacteria that gives them terminal bellyache. It should take them out pretty well.

--Alison

I've got the horn worm. It is green, the size of my index finger and covered with wasp larvae who are feeding off the bugger. I picked off two so far. What kind of chemical can I put on there to prevent future ones? I have 8 plants to inspect tonight. I found the two about 5pm. I have read that evenings they come out and that is the time to find them. Please help. I love my tomatoes and I cant bear to lose not one of them! Thanks.