Something is eating holes in my new broccoli plants. Should I be worried, and if so, what should I do?
If you look very closely on the undersides of the leaves, especially along the leaf veins, you will spot the culprits — green worms (see photo) that have hatched from eggs laid by white cabbage butterflies and their cousins. Beneficial insects and birds will reduce the number of worms but broccoli, cabbage and related brassicas often need some human help to fend off these fast-growing butterfly larvae. Our recent online poll shows which methods are most popular.
The Bt product is a good choice; it's made from a bacteria and it only kills the worms that eat it; it won’t harm other insects, pets or humans. Johnny’s Selected Seeds offers a brand (Dipel) as either a dust or a powder that you mix with water and spray. This "dry flowable" powder will last "indefinitely" so you won’t have to buy it fresh every year. And Peaceful Valley Farm Supply sells nifty Solo sprayers that have trombone extensions and adjustable nozzles so that you can get the spray onto the undersides of the leaves, where the caterpillars like to hang out.
— Cheryl Long, editor in chief