Brassica Collars

Brassica collars may sound like Elizabethan neckwear, but these simple DIY tools can protect members of the cabbage family from the dreaded cabbage maggot.

Cool season crops, such as broccoli, turnips, rutabagas, cabbage, Brussels sprouts, are all susceptible to cabbage maggots.

Paperboard brassica collar

Cabbage maggots

Also known as cabbage flies, root flies, or turnip flies, cabbage maggots start out as tiny flies (Delia radicum) that are about half the size of a housefly. These pests lay up to 300 eggs in the soil, around the crown of host plants. When the eggs hatch, the larva (maggots) begin feeding on fibrous roots and burrowing into taproots. This feeding facilitates entry by pathogens that cause blackleg and bacterial soft rot. Heavy infestations can kill a mature plant. Infested plants should be removed and thrown in the trash. They should not be composted.

How do brassica collars work?

A brassica collar is simply a flat piece of plastic, thick cardboard, felt, rubber, or heavy fabric that covers the soil around the base of a plant. Brassica collars protect members of the cabbage family from cabbage maggots by making it difficult for the fly to reach the soil closest to the plant stem. This forces the fly to either lay its eggs elsewhere, or to lay them so far from the plant that the eggs dry out before they can hatch, or causing most of the larva to starve before they ever reach the plant.

How to make a brassica collar

While you can certainly buy brassica collars for your plants, these simple tools are just too easy to make at home with materials from your recycling bin to not try at least once. Personally, I prefer cardboard. It is easy to work with and will ultimately decompose. Just follow these steps to make your own brassica collars:

1. Cut cardboard into 6- to 8-inch circles or squares.
2. In the center, cut an 2-inch ‘X’ with a razor or box cutter.
3. Fold the flaps of the ‘X’ back and forth, to make them more flexible.
4. Gently install the collar by inserting the seedling through the hole in the center.
5. Position the flaps so that they cover as much of the opening as possible, without damaging the plant stem.

If you are worried about damaging the seedling, you can cut a line from the outer edge to the center hole and wrap the brassica collar around the seedling that way. You will then have to staple the cut edges together for the collar to be effective. Just be sure that the collar opening can be enlarged as the plant grows.

As an added benefit, brassica collars also block weeds and they help keep the soil temperature and moisture levels stable