Defending Your Garden Against Cabbage Loopers


get_image.jpgBy Caitlin Harwell

Cabbage loopers and cabbage moths are one of the most damaging garden pests and can devastate a garden in only a few days. They are especially attracted to brassicas like collard, cabbage and broccoli plants but are known to devour turnip leaves, spinach, cucumbers and even tomatoes. They can be found throughout North America and have been known to overwinter in southern states.

How do you know if there are Cabbage loopers in your garden? The loopers are the larval form of the white cabbage butterfly, and their appearance is often the first sign that an infestation may be on its way. The small, white butterflies usually only appear in the night, which is why most infestations are not found until the damage appears on leaves. Cabbage moths will lay eggs on the underside of leafy plants, which is why brassicas, with their thick, fibrous leaves are a preferred sanctuary for loopers. When the larvae appear they are initially a milky white color and will develop into plump green caterpillars, with faint white stripes on the sides of their back. Once they have reached the larval state these eating machines can consume more than three times their weight in a single day.

If they are not discovered early, the caterpillars become very difficult to control. There can be anywhere from 3-7 generations of caterpillars throughout the growing season depending on the temperature.

So what can you do to keep them out of your garden? Before you tear your garden apart in frustration (like a certain gardener did her first year) try some of these helpful tips:

Keep Clean: Cleaning up your garden at the end of the season is more of a preventative measure. Make sure that any greenery and debris is collected, removed and disposed of before winter sets in, as the cabbage looper is known to overwinter in gardens. If you have a larger garden it may be worth tilling before the ground hardens, just to make sure you got every last one.

Pick'em: Some people are very turned off by the idea of handling these squishy little pests, but if you only have a few, it beats investing in other expensive and time-consuming alternatives. Just throw on a pair of gloves, grab a bucket and diligently search every leaf (it could all be for naught if you leave even one). Make sure to dispose of the critters far away from your garden, and your neighbors'. If you already have a large infestation, this may be an exercise in futility and you may want to look at some of the other options.

Flowers and Herbs: Plant strong smelling flowers and herbs like marigolds, nasturtiums, mint and chives around the other plants in your garden. These odors deter insects, including cabbage butterflys, from entering the garden and laying eggs.

Floating Row Covers: So they are not the most attractive addition to any garden, however, if you are struggling with the voracious cabbage looper, they might be worth a second look. Floating row covers are a light-weight fabric made from polypropylene and polyester that you drape over plants and secure to the ground with rocks, lawn staples or other materials you have handy. They are common enough that you can pick some up at your local garden center and are less pricey than other pest defense options. As long as you get them down before the cabbage moths have a chance to lay their eggs, and there aren't any overwintering in your garden, you will be caterpillar free for the season. This method works particularly well for long rows of plants. The big pros to floating row covers is they protect against frost and keep plants warmer, which increases growth rates, and you can water directly through them without having to remove or reapply. When using row covers, make sure you leave enough slack for your plants to grow.

DIY Bug Deterants: Certainly a more appealing solution to organic gardeners than chemical insecticides, making your own deterrent spray can be effective and easier on your wallet. In a sprayer bottle, mix liquid dish detergent, hot sauce, vinegar and water and apply the brew on the tops and bottoms of your plants' leaves. This mixture will not kill any hungry caterpillars, but the taste and smell will deter them from munching on the coated leaves. This is usually an effort that must be combined with other methods of fending of the loopers and, in most cases, will not be 100% effective on its own.

Bacteria: It sounds scary but there is actually a naturally occurring bacteria that is known to attack caterpillars and only caterpillars. It is known as Bacillus thuringiensis, or BT. Most gardeners consider BT an organic alternative to other store bought pesticide products and it is very effective against cabbage loopers. Certain strains of BT affect caterpillars the same way other bacteria affect humans. In this case BT poisons the caterpillar by way of its stomach, therefore the caterpillar must ingest BT for it to be effective, so timing is everything. It is commonly sold as a powder that you can then mix with water and spray over your plants. Keep in mind that more than one application may be necessary. BT is a living organism and can only live outside of a host for a few days to a week and too much rain or sun can also reduce its effectiveness. While BT can be the most effective solution to cabbage loopers, it is not a miracle product. One of the downsides of BT is that it can adversely affect other caterpillars, including butterfly larvae. Research the product before purchasing or applying to your garden so you make sure you are using the correct strain and understand the application process.

There is no absolute solution to dealing with any pest in the garden and cabbage loopers are no exception. However, with the gardener's spirit and a little hard work your cabbage looper problems will become a thing of the past.

Cait Harwell has been gardening and farming for a good portion of her life and has developed skills in small industry vegetable production and farm maintenance. She lives in the Northeast where she has a small garden homestead and cultivates everything from squash and tomatoes to exotic plants. She recently received her Masters in Writing from FDU and hopes to pursue her life-long dream of owning her own farm.