There are several insects and maybe all of these that will eat the foliage of turnips and pumpkins. Slugs, snails, earwigs, green worm or larvae of cabbage moth and other caterpillars. Look on the back of the leaves for green worm-- like caterpillars and squish them. Set out a pet safe slug bait or lure slugs to a saucer of beer, and set a clay pot stuffed with straw or rotten fruit on it's side near the plants. The coolness of the clay and smell of the fruit will attract earwigs, sowbugs and slugs and snails at night and you can dispose of your catch each morning. You can also lay down a wooden board near the plants and check under this each day for the enemy. Don't worry your turnips and pumpkins are most likely going to outgrow the problem if you start hunting for the culprits now and get control before summer wears on. Keep growing, Marianne Binetti