If you have pretty white moths with a black spot on each wing and a lot of holes in your lovely cabbage, broccoli and other cole crops, the cabbage moth has probably come to visit. The damage to your crops is not caused by the moths themselves, but by the furry green caterpillars that hatch from the yellow eggs they lay on the undersides of the leaves. Luckily, according to Organic Gardening for Dummies by Ann Whitman, the adult moths are attracted to yellow sticky traps which can be made quickly and cheaply with items you likely already have around the house.
Select an appropriate material for your sticky traps. The most common are plywood or heavy cardboard, but use what you have available. Plastic plates, plexiglass and glass also work.
Cut the plywood to an appropriate size with a saw, if necessary. Use scissors to cut the cardboard. Common sizes for commercial traps are 3 inches by 5 inches, but commercial growers often recommend and use much larger sizes, such as 12 inches square.
Spray paint at least one side yellow and let dry completely.
Determine how and where you will mount your traps. Attach them to garden stakes or a nearby fence. Place them close to the affected plants but far enough away that the leaves will not brush against the yellow sticky trap.
Attach the prepared trap in the desired location and then spread with a coating of petroleum jelly or used motor oil.
Check the traps weekly and either replace or reapply another coating of oil to maintain effectiveness.