You have a caterpillar infestation, Caterpillars!!! Argh!!! Sometimes the first sign of caterpillars / worms / cabbage loopers is just seeing chunks of your leaves missing. You may also see clumps of black/brown “dirt” on your leaves, which is caterpillar poop. Lastly, you may actually catch a caterpillar munching on your leaves. It can be so angering to catch them in the act!