The following information was suggested by Elizabeth Beggins whose bed (#29) in the St. Michaels Community Garden has been overrun by Harlequin bugs. The information below can be found in its entirety at http://www.toxicfreenc.org/organicgardening/stink_bugs.html. The photos are also from that website. The photo of the eggs is helpful. Barrel shaped and distinctive. One more thing to look for.
Adult Harlequin Harlequin nymphs
About Harlequin Bugs and Stink Bugs
The Harlequin bug is a type of stink bug that causes trouble for many gardeners in the Southeast. Other stink bug pests in North Carolina include the Green stink bug, Brown stink bug, and Southern green stink bug.
All are pests of many crops, but they especially love plants of the brassica family. The brassicas include cabbage, collards, broccoli, mustard, turnips, and kale. During heavy outbreaks, or when all their favorites are gone, Harlequin bugs will eat other garden plants such as squash, okra, tomatoes, corn, beans, and tree fruits.
Both adults and nymphs cause damage. They eat all parts of the plants, including stems, leaves, fruits, and seeds. They use piercing mouth parts to suck out plant juices. Damage on leaves and stems looks like uneven discolored spots around a hole. Young plants may wilt, turn brown, and die. Mature plants may survive but growth is slowed. Damage on fruits such as squash, tomatoes and okra appears as dark holes surrounded by bumps, pits, or white-yellowish spots. The lighter spots do not ripen to the same color as the rest of the fruit. Fruits may also dimple or grow in strange shapes.
The tips below are designed to help you control stink bug damage in your garden. Sustainable pest management strategies usually work best when used together. Think about your garden, your resources, and your time, and put several of these tips together into a plan that works for you.
Identifying Harlequin Bugs and Stink Bugs
Adult stink bugs are about half an inch long and shield-shaped. Their colors range from dark brown, tan, to green. The Harlequin bug is black with orange, yellow and red markings (see picture above).
Nymphs are similar to adults but smaller and with a more rounded shape. Eggs are barrel-shaped. They are laid in groups on stems and the undersides of leaves, and may be yellow, green, pink, gray, or striped. (see picture above)
Stink bug eggs
It is important to note that not all stink bugs are pests. Some predatory stink bugs, such as the spined soldier bug, actually attack other garden pests. They should be encouraged in the garden. The spined soldier bug looks similar to the brown stink bug, but has spikes standing out on its shoulders.
Stink bug adults spend the winter in old plants and other garden litter. They come out in the early spring to begin laying eggs. In early spring eggs take up to 20 days to hatch, but as the weather warms they may hatch in as few as 5 days. Nymphs mature into adults in 5 – 8 weeks. Populations tend to grow through the season, getting heaviest during early to mid fall.
1) Grow healthy organic plants. Strong plants can handle some damage from stink bugs better than weak, struggling plants. Make sure that your crops are getting enough sunlight and water. Ensure that the soil is well-drained, and rich in nutrients and organic matter.
2) Grow resistant varieties. Some types of brassica plants are naturally resistant to Harlequin bugs. NC Cooperative Extension recommends the following varieties: Cabbage: Copenhagen Market 86, Headstart, Savoy Perfect Drumhead, Stein’s Flat Dutch, Early Jersey Wakefield. Collards: Green Glaze. Cauliflower: Early Snowball X, Snowball Y. Radishes: Red Devil, White Icicle, Globemaster, Cherry Belle, Champion, Red Prince.
3) Till in late fall. Tilling crop leftovers into the soil once cold weather has arrived can reduce the number of adult stink bugs who survive the winter. Then fewer come back out the following spring.
4) Control weeds in the garden area. Stink bugs are attracted by weedy areas in or near the garden. Weeds should not be allowed to spread in the garden. Weedy areas around the garden should be mowed before spring planting and regularly after that to keep stink bugs from hanging around.
5) Use row covers. Keep stink bugs from finding your crop by covering your brassica plants with a lightweight “floating” row cover such as Reemay. These materials (as opposed to plastic or heavier fabrics) let water and air through and do not block very much sunlight. They can be found at garden supply stores or ordered from seed catalogs. The covers can lie directly on the plants (the plants will lift the cover as they grow), or you can support the covers with wire hoops. The trick is to keep the edges of the covers tightly buried or weighted so that the stink bugs cannot get in.
Getting Rid of Harlequin Bugs and Stink Bugs Without Toxic Chemicals
6) Scout and hand pick. Hand picking stink bug adults, nymphs and eggs early in the season can really help you control them later in the year. Likewise, hand picking in the fall can cut down the number of adult stink bugs that come back the following season. Scout the garden often throughout the year. When you find stink bug adults, nymphs, or egg clusters, crush them with your fingers. Or, since stink bugs really do stink when you squish them, it might be less smelly to drop them into a pail of soapy water.