Cabbage loopers, or Trichoplusia ni, are potentially disastrous caterpillar-like insects named for the loop-like shape their bodies make when they crawl. They love cruciferous vegetables, particularly those in the brassica family, and can plague a garden for an entire season.
Luckily, implementing solutions in a timely manner can eradicate them before too much damage is done.
Cabbage loopers leave pretty characteristic signs. Aside from sightings of the little green caterpillar itself, they make themselves known by chewing irregularly shaped holes in the leaves of your cruciferous vegetables. You will also see brown waste from their feasts on leaves, and severe infestations can render your plants incapable of growing at a healthy rate.
In an ideal world, you’ll never have to wage a war against these destructive little loopers. There are several things you can do to better your chances of deterring them throughout the season.
Unfortunately, some degree of cabbage looper infestation is likely no matter what you do. If things get out of control, there are very effective organic and pesticide-based options available to reassert control over your garden.
If your problem is mild or you catch it early, simply pick the larvae off by hand and drown them in soapy water. The eggs can be brushed off and met with the same end.
Cabbage loopers will overwinter on plant debris, making re-infestation likely, so removing all plant debris at the end of the season helps lessen the chance of this happening.
Use BT spray
This sounds inorganic, but it’s au naturale—BT, or Bacillus thuringiensis, is a spray made from bacteria that kills cabbage loopers. Use the spray early in the infestation for the best results.
If organic control isn’t important to you or if the above methods have proven ineffective, insecticides are an option. There are two ways to go about this: