Not Every Stink Bug in Your Garden Is the Invasive One

How to know it’s brown marmorated stink bug

Check the antennae. Two white bands settle this question faster than size, color or shape, all of which the native look-alikes share.

Adult:

A typically shaped stink bug about five-eighths of an inch long and marbled brown, with two white bands on the antennae, a blunt front edge to the head, a smooth shoulder margin, and legs marbled brown with faint white banding.

The abdomen edge:

A banded edge visible along the side of the folded wings, and dark bands at the tips of the membranous parts of the forewings.

Egg:

Barrel-shaped, white to pale green, laid in clusters on leaves.

Nymphs:

Five stages, from about 2.4 mm to 12 mm. Newly hatched nymphs have an orange abdomen with dark plates and cluster around the egg mass; later stages are marbled brown with white bands on the antennae and legs and spines in front of red eyes.

The year it runs on

Generations: One or two generations a year in the mid-Atlantic, with more in warmer regions.

Where it spends the winter: As an adult, in a resting state, in protected places — which for this insect very often means inside a building.

1. Fall: Adults aggregate in large numbers on the sides of buildings and on trees, then move into protected places to overwinter.
2. Winter: Adults do not reproduce and barely feed. They hide in narrow spaces indoors — behind baseboards, around window and door trim, around ceiling fixtures — preferring high, cool spots.
3. Spring: Adults become active and move from overwintering sites out to host plants. After roughly two weeks of feeding, they mate.
4. Through the season: Females lay eggs in clusters of 20 to 28, and between 212 and 486 eggs over a lifetime.

The one-or-two generation figure is UC IPM’s for the mid-Atlantic; UC IPM states plainly that the number of generations across much of California is unknown, noting only that warmer regions generally see more. That honest gap is worth carrying: the count where you live may simply not be established.

What the damage actually costs you

This is a fruit pest above all. Adults and nymphs inject tissue-destroying enzymes and suck the juices out of fruit and seeds.

• •Pockmarks and distortions on fruit that make it unmarketable, with the flesh underneath turning hard and pithy.
• •Damage concentrated on apple, pear, peach, nectarine, lima bean, snap pea, pepper, sweet corn, tomato and soybean — the mid-Atlantic crops UC IPM lists as most affected.
• •Feeding on buds, flowers, leaves and stems, including through the bark of young trees.
• •Indoors, an offensive odor when the insects are disturbed or crushed.

How much the plant can take: Low on fruit, because one insect feeds on many fruits and losses compound quickly. Indoors, though, the honest answer is that the nuisance is the whole problem: UC IPM is explicit that these bugs are not harmful to people, houses or pets, do not bite or sting, do not spread disease, do not eat or bore into wood, and will not reproduce or cause damage inside a structure.

The move

Identify first, then exclude and remove by hand — the sprays mostly do not earn their place. From the UC IPM Pest Notes and University of Maryland Extension:

1. 1

   Check the antennae before you act

   Two white bands on each antenna means the invasive one. No antennal bands with a rough, two-pointed head edge is the native rough stink bug; plain antennae with dark-spotted legs and a banded abdomen edge is the native consperse stink bug. A short, thick beak means a predator — leave it be.

2. 2

   Hand-pick, and destroy the egg clusters

   They are large enough to knock into soapy water, though they hide in dense foliage and drop when startled, so a dedicated hand-held vacuum used regularly works better on a real infestation. Look for the barrel-shaped egg clusters on leaf undersides and destroy those too.

3. 3

   Row-cover, but not while it is flowering

   A row cover prevents stink-bug feeding outright — but it also keeps pollinators off the flowers, which may be exactly when protection is wanted. Cover selectively, and expect it to be impractical on a full-size fruit tree.

4. 4

   Keep any pheromone trap away from the rows

   Traps are useful for telling you the bugs have arrived, but probably not for preventing damage. In a 2013 Maryland home-garden study, a single pheromone trap set a meter from the garden rows produced more stink bugs and more damage on the nearby plants — a spillover effect worth avoiding in a small yard.

5. 5

   Seal the house instead of spraying it

   In fall the adults move indoors to overwinter, where they do not reproduce, feed, bite, or damage the building. Caulk the gaps around windows, doors, utility pipes and vents, repair screens and fit door sweeps: exterior sprays break down within days, and sealing is both more effective and more environmentally sound.

Sources: University of California Cooperative Extension (UC IPM). Pest Notes: Brown Marmorated Stink Bug (UC ANR Publication 74169); University of Maryland Extension (2021). Predatory Stink Bugs; NC State Extension (2018). Spined Soldier Bug Look-a-Likes

The plants in this playbook