There are many types of pesky worms that can cause damage to your tomato crop including pinworms, fruitworm and hornworms. Some pests can be controlled by handpicking, insecticidal soap and parasitic insects but some may need to be controlled by Sevin dust. Pinworms are about ¼ inch long and are yellow greenish or purplish black with brown heads. Look for webbing inside on the inside of your leaves and pinholes at the base of the stem of developing flowers and the tomatoes. The fruitworm will cause damage to the actual tomato on the plant. You should look for a small hole bore at the bottom of you tomatoes. Parasitic wasps can be a great way to control the fruit worm. Hornworms evolve into a moth and are green and are very difficult to see. They can reach 3 to 4 inches in length at maturity. They will chew on your leaves and your tomatoes. You could first try handpicking a mild infestation. You can make your own insecticidal soap by adding 4 teaspoons of liquid soap, onion horseradish, garlic, cayenne pepper to 2 quarts of water, boil, put in a jar with a lid on it and let it sit overnight. Strain and then transfer the concoction to a spray bottle. If you do not need this much you can cut the recipe in half and freeze any remaining. Because it is a pesticide and pesticides carry with them the danger of affecting human health, I only recommend putting Sevin dust when you have no other alternative. Don’t use on the actual tomato but put it around your plant and on the leaves. You should always thoroughly wash your tomatoes before eating them. At the end of the season till your soil and it will kill many of the larvae left behind by these pesky worms. If you are not sure what type of pest is affecting your plants the internet is a great resource and will provide pictures along with ways to control them.