Controlling Common Garden Pests: Cabbage Loopers and Cabbage Moths

In my last post, I talked about several ways that you can prevent common garden pests from ever even arriving at your vegetable garden.  I talked about the ideas of vegetable rotation, inviting beneficial insects, and choosing the pest resistant vegetables and varieties. These measures can go a long way in managing pests. 

Even so, and even with the very best prevention practices, some number of pests are just an inevitability.  That being said, when we do find pest presence in our gardens, there are many measures that can be taken to exclude, harass, banish, and yes... eliminate these unwanted visitors.  And it can all be done without harmful and dangerous chemicals using entirely organic methods and products!

Close up of mature Cabbage Looper larvae

Close up of mature Cabbage Looper larvae

I will be posting periodically about common garden pests in the Portland area and the Willamette Valley.  Since each garden pest is unique, requiring different approaches, I will tackle them one at a time discussing how to identify them, what vegetables they most commonly affect, and how to deal with them!!!

It should be stated first, that aside from the prevention techniques I discussed in the last blog post, early identification and action are the best way to control garden pests!  This is yet another invitation for you to be a keen observer in your garden.  I truly believe that close observation and attention are the most important skills a gardener can have.

In today's post I am going to talk specifically about Cabbage Loopers.  These small green caterpillars can do serious damage to a whole range of vegetables, not just cabbages!  The name is apt however, since Cabbage Loopers are most commonly found in vegetables from the Cabbage or Brassica family.  Some of the most susceptible vegetables to Cabbage Loopers include kale, broccoli, cauliflower, bok choi, cabbage, and collard greens.  Cabbage Loopers are pale green, and have faint white stripes that run the length of their bodies.  They are called loopers for their "looping" movement (think inchworm).


Cabbage Loopers have voracious appetites and do most of their damage by consuming leaf tissues, eating large holes in leaves, and even boring into mature cauliflower and broccoli heads.  They can also cause damage by leaving their frass or waste in enfolded leaves of cabbages and broccolis.  Loopers are generally easy to see, feeding throughout the day, and at up to an inch long, they are large as far as invertebrate garden pests are concerned. 

Cabbage Loopers going to work on leaves of collard greens

Cabbage Loopers going to work on leaves of collard greens


Several species of parasitic wasps prey on cabbage loopers, and so planting for beneficials that attract these wasps can be effective in controlling populations.  The flowering plants of the carrot family (carrots, parsley, cilantro, celery, dill, fennel...) provide excellent pollen and nectar sources for parasitic wasps, so letting these herbs and vegetables go to flower can have an indirect effect on controlling Cabbage Loopers!


Providing nectar and pollen sources for parasitic wasps is a great way to encourage the natural predators of Cabbage Loopers in your garden!

Providing nectar and pollen sources for parasitic wasps is a great way to encourage the natural predators of Cabbage Loopers in your garden!


Once the caterpillars have hatched, they are quick to grow, and it doesn't take much time for them to cause significant damage in the garden.  For this reason, the best time to control Cabbage Loopers is early in their life cycle.  An excellent way to establish early control is to identify their tiny pale green eggs, which are often visible on the undersides of the leaves of affected vegetables.  Removing and smooshing eggs is a great first step.

Once the larva hatch and begin consuming your vegetables, other measures are often required for control.  The most effective organic product that I have found for controlling Cabbage Loopers is Bt which stands for Bacillus thuringiensisBt is a bacteria that, when consumed by Cabbage Loopers, causes severe and ultimately lethal digestive disruption.  It is completely natural, entirely safe for human contact and consumption, and does minimal damage to other beneficial insects.  There are many commercial products containing Bt, and as long as they are OMRI (Organic Materials Review Institute) certified, you can be sure that they are safe and benign for humans.

Safer Brand Caterpillar Killer (above), and Monterey B.t. (below) are two effective commercially available forms of Bt.

I hope this is helpful to those of you who have had to deal with these little devils in the past!  Cabbage Loopers can be a real pain but with early identification and a proactive approach, you should be able to keep them at a healthy distance and enjoy your cabbages, etc... as you truly should!  Happy gardening and stay tuned for my next blog post about planting your Fall and Winter vegetable gardens!!