Planting and maintaining a garden can be a practical and rewarding undertaking. Gardening also includes some amount of effort, so it can be especially frustrating when unwelcome pests appear. There are multiple species of black and orange insects that are commonly found in gardens. Some of these can be damaging and warrant control, while others are actually beneficial insects that control the populations of damaging pests.
Adults and nymphal harlequin bugs (Murgantia histrionica) are orange and black. The adult bug is a gaudy, shield-shaped stink bug three-eighths inch long. This pest sucks on plant juices, causing the plant to wilt, brown and die. Its preferred hosts are crucifers like cabbage, cauliflower, mustard, radish and others but it will feed on a number of additional plants. Hand-picking can control small numbers of this pest. Another method is to use a trap crop like turnip before or after the growing season to attract, then destroy the gathered masses of harlequin bugs.
Juvenile Green Stink Bugs
The nymph of the green stink bug is predominantly black when young but it matures to become green with orange and black. Like the green adult, the nymph is shield-shaped and feeds on a number of different plant species using needle-like mouth parts, causing varying types of damage depending on the plant and plant part. Weed control near the garden may help to limit stink bug numbers but insecticide use is the most reliable control method.
The spotted asparagus beetle (Crioceris duodecimpunctata) is one-fourth inch long and reddish-orange with 12 black spots. This pest feeds on asparagus, causing spears to bend, turn brown or develop scars and reduces the plant's ability to stockpile nutrients. Control the asparagus beetle by handpicking, remove plant residue from around the asparagus and, if necessary, apply an insecticide.
Colorado Potato Beetle
The Colorado potato beetle (Leptinotarsa decemlineata), also known as the potato bug, is a major pest on cultivated potatoes. The adult beetle is less than one-half inch long, oval and has a yellow-orange body and wing cover with 10 narrow black stripes. Both adult beetles and the red to salmon-colored larvae feed on the leaves of potato as well as eggplant, pepper and tomato and can cause severe defoliation, which affects tuber development. Control this pest by removing weeds like nightshade and ground cherry from around the garden, choose an early-maturing potato variety and handpick adults, larvae and eggs off of leaves. Insecticides are generally ineffective against the potato bug.
Striped Cucumber Beetle
The striped cucumber beetle is pale yellow or orange with black stripes on its wings. This pest feeds on all parts of cucumbers and related plants and can transmit bacterial wilt. Protect plants using netting or screens or apply an insecticide.
Beneficial Black and Orange Insects
A number of black and orange insects that are often found in gardens do not harm garden crops and instead are beneficial, eating pests that do. Ladybug adults, widely-recognized orange insects with black spots, as well as their similarly-colored larvae, feed on aphids, chinch bugs, mealybugs, thrips, whiteflies and spider mites. Syrphid flies resemble bees or wasps and often hoer around flowers. The syrphid fly larvae feeds on damaging insects. Soldier beetles, assassin bugs and predacious stink bugs are also black and orange beneficial insects.