Brassica plants love our fall weather. So do harlequin bugs. And unfortunately harlequin bugs love brassicas. These colorful bugs are attracted to the large, succulent leaves of various members of the brassica family, including broccoli, cauliflower, kale, collards and mustard. A cousin to stink bugs, the adults are easy to spot because of their orange and black exoskeleton, and if you find one there are usually many more in the vicinity.
One of the best methods for controlling this pest is to perform a regular “search and destroy” operation to keep them in check; otherwise they will continue to proliferate in your garden. Monitor your plants for clusters of the distinctive, black and white barrel-shaped eggs which are usually laid in clusters of 10-12 on the plant stems or the underside of leaves. Each female egg has the potential to hatch and grow and lay another dozen eggs in only four to nine weeks, so if you can eliminate just one egg mass you will be way ahead in this game we call vegetable gardening.
Organic products, such as spinosad or insecticidal soap, only offer fair control and are most effective in the nymphal stages. Adults become more resistant and harder to control so find those eggs and destroy them! If any eggs should escape your eagle eye, hand pick the resulting pests and drop them into a bucket of soapy water. Row cover can be used to protect plants, just make sure there are no adults or eggs present before covering plants. Another control option is to plant a sacrificial trap crop of mustard or turnips to attract the bugs away from your desirable plants, then pick off the adults or spray the trap crop with insecticide rather than spraying all of the brassicas you plan to eat. Keep an eye out for this pest in both fall and early spring as they can easily decimate a plant if not kept under control.