"Some people think very much of turnips, parsnips and rutabagas as food, but many insects like them even less. Dr. E. P. Lichtenstein and his co-workers... have isolated materials from all three vegetables that can kill a number of insect pests, including vinegar flies, Mexican bean beatles, mosquito larvae, houseflies and mites. There is also strong evidence that the roots of cabbages, cauliflower, Brussel sprouts, kale, mustard and kohlrabi have this same built-in protection against the insect world, says Dr. Lichtenstein."