Cabbage White Butterfly
(Grand Forks, B.C. Canada)
damaged leaves on collards
Although pretty in flight, if you're a grower of cabbages, broccoli or any other brassica, this butterfly will get your blood boiling.
This European import is a destructive pest, making lace out of your best crops of any of these related plants.
The adult is very fluttery, and extremely hard to photograph, and the larva are tiny green caterpillars and rarely seen until the damage is done.
They will eat huge holes in the leaves, and leave behind their frass or droppings, making it inedible.
If you see these fluttering white butterflies in your vegetable garden, make sure you rinse your broccoli in salted water for a few minutes to get the caterpillars out.
A sure fire way to prevent damage is to cover your crop top to bottom with row cover to keep the adults out.
You can use Bacillus thuringiensis against the larvae, which is a naturally occurring bacterial infection which gives them a tummy ache, and eventually they starve to death. I'm unsure if this has an effect on other more desirable types of butterflies, so I don't use this method, but it is considered to be an organic form of pest control.