Tomato Crisis

I went out to the garden today to check on my tomato plants and noticed that one of them had a bunch of leaves missing. Not only leaves, but entire little branches just snipped right off. I started investigating and found these brown raisin type things sitting on all many leaves. Upon further inspection I found the culprit. A big fat HUGE tomato worm. I never knew a thing like that could eat so much and well..poop so much. How in the heck do they know where tomato plants are? Are they just creeping down the road and sniff and say "I smell tomatoes" and turn in the drive? I remember Grandma finding those things and she would just pull them off, throw them to the ground, and step on them. I couldn't do it. So I got out the rubber gloves, pulled it off, and flung it out in the field, which was probably a mistake as it will find it's way back. I checked the other plants and found a little one, and did the same. I think I have a problem and if action isn't taken soon, they will eat the whole darn plant. THIS IS WAR!