If it is cabbage worms or cabbage loopers then Bt is the recommended treatment for them. It is sold under several brand names like Dipel and Turicide and sold at most garden centers. You'll find many discussions here about it.

If it is something else then can't really help with control without knowing what it is. First rule of pesticide use is first you have to ID the culprit.

Dave

Sometimes those cabbage worms are very hard to see, since they have excellent camouflage. Do you have pretty good eyesight? Do you have wasps in your garden? They help control these caterpillars in my garden. I also sometimes spray with BT when they start causing lots of damage. And I have a badminton racket which I use sometime to kill the white butterflies I see flying around. (its hard to do, its amazing how fast they move)

I'm enjoying the image of ccabal prancing about swiping butterflies with a badminton racket ;-)

I do have pretty good eyesight and I couldn't see anything on the leaves at all...are there other common culprits I should be considering?

I think my son would get a kick out of using the racket, but my neighbor studies cabbage butterflies so he might not like it so much...:)

Why kill white butterfly's? We always have them in our gardens, never noticed any damage from them. This is a serious question by the way, should I be concerned about them?

The Cabbage White butterfly searches out and lays eggs on cole crops. The eggs hatch creating hungry caterpillars that can quickly decimate the leaves.

If you don't have cole crops, you may not have experienced their damage first hand.

Give your son a butterfly net and have him 'collect specimens' for your neighbor to study far away from home lol.

Hmmm, so those are what's laying the worms in my broccoli? Then they must die lol. Strangely enough they don't invade the Brussels sprouts. Glad I asked!

Around here, they tend to wait until the end of summer to go after the Brussels sprouts. Mid to late spring, they go for the broccoli and kale.

Look under the leaves. The caterpillars start off as small slightly yellow transparent looking and are only a few mm long. Once around 5 mm long they are green. The same shade of green as brussels sprout leaves. I just squash them between my fingers. I did my plants today. Each plant with damage had at least one caterpillar on it. I rub off any eggs I see also. Obviously my hand treatment is for small scale garden. Don't assume they moved on, they are there to be found.

Okay, thanks I will go out and look more closely. So far they seem to be leaving my kale and broccoli alone, but I don't imagine that will last for long.

cabbage loopers

look along the main vein of the leaves, under, over...they blend in very well.

pull them off and dispose of them.

our brussels sprouts were looking pretty holey...spent time removing and the plants are now bouncing back. we are organic.

Thank you! Are they green? Once I remove them, will they come back?

The only prevention is to cover your cole crops with row cover or very fine netting. You can spray for the caterpillars that are already there but more will come to replace them.

Slugs & snails like cole crops too - & they feed when it's dark. Also, there are some types of caterpillars that feed in the wee hours & hide during the day. There is a product for snails/slugs made from iron phosphate that takes care of them w/o ill effects to anything else - it eventually breaks down into fertilizer.

I just squish caterpillars right on the plants, don't bother pulling them off.

A picture is worth a thousand words & all that...

Hello, I had the same issue last year. You need to look real close the worms are the same color as the leaves. I believe if you see little black things on the leaves that is a sure sign of them. Look close. What I ended up doing was going to town on them and picking and squishing them. Also used a little dish soap and water. Spray on and it should help. After each rain fall you need to spray back on.

Thanks so much. I looked at them again today and did see some teeny tiny white dots that I pulled off. Eggs perhaps? I will definitely try the dish soap and water.

Yeah that would be the eggs! Dish soap and water kicks butt! I used it on my green beans and broccoli.

Do you just spray it over the tops or do you go leaf by leaf to get the underside as well? Is there a certain concentration you used?