Types of Stink Bugs: Which Are Pests and Which Help

Shield-shaped, slow, and quick to smell. But some of the ones in your garden are eating the pests, and the invasive one is told apart by two white bands on the antennae.

Telling them apart

The invasive one

The brown marmorated stink bug arrived in Pennsylvania in the 1990s and has spread across most of the United States and into Europe.

What makes it different from the natives:

• An enormous host range — fruit trees, vegetables, ornamentals, field crops, over a hundred species
• No effective native predators, so populations build unchecked
• It overwinters indoors in large numbers, which the natives mostly do not
• Real commercial damage, particularly to apples, peaches and soybeans

In a garden it is a nuisance rather than a catastrophe. In an orchard it is a genuine problem.

The damage

Plant feeders pierce fruit and pods with a needle-like mouthpart and suck sap. The plant walls off the wound, which is what you see later:

• Tomatoes — pale, hard, corky patches under the skin, called cloudy spot
• Peaches and apples — sunken dimples and distortion, called cat-facing
• Beans, okra, peppers — dimpled, distorted, sometimes aborted pods
• Sweetcorn — shrivelled or discoloured kernels

It is cosmetic at garden scale. The fruit is edible — cut out the corky patch. Nothing is poisoned, nothing spreads.

Outdoors, in the garden

Honest order of usefulness:

1. Hand-pick into soapy water. They are slow and obvious in the morning. On a garden’s worth of plants this is genuinely the most effective control
2. Row cover over vulnerable crops before the bugs arrive
3. Clear weedy edges and debris where they shelter, though not at the cost of habitat for predators
4. Leave the predators alone — soldier bugs, assassin bugs, parasitic wasps and birds all take stink bugs
5. Sprays last, and reluctantly. Broad-spectrum insecticides kill the predatory stink bugs along with the pests, and stink bugs re-invade from outside the treated area within days

Indoors, in autumn

The brown marmorated stink bug overwinters as an adult, and a heated house is the best cavity it will ever find.

What works — before they arrive:

• Seal in late summer. Gaps around windows and doors, vents, soffits, utility entries, chimney and siding gaps
• Repair screens and fit door sweeps
• Reduce outdoor lighting on the walls in early autumn, or switch to warmer colour temperatures

Once they are in:

• Vacuum them up. Empty the bag or canister outdoors immediately — the smell survives in a vacuum for weeks otherwise
• A dedicated shop-vac, or a stocking-over-the-hose trick, keeps the machine clean
• Do not squash them. The fluid stains fabric and the smell lingers
• Do not spray inside walls. It cannot reach most of them, and hundreds of dead bugs in a wall void attract carpet beetles, which are a worse problem than the stink bugs were

They do not bite, breed, feed or damage anything indoors. They are waiting for spring, and on warm winter days they wake up and appear at windows. That is the whole of it.

The smell

Released from glands on the thorax when the bug is crushed or alarmed — the compounds are aldehydes, and people describe them as coriander, burnt rubber or old socks.

It is a defence, not an attack, and it does not attract more stink bugs to the spot despite the common belief. Handle them gently and most never release it at all.