Say Stink Bugs

When I say ‘stink bug’, you probably think of a green or brown shield-shaped bug, and you’d be right.

But Say stink bugs (Chlorochroa sayi) can be such a dark green that they look nearly black with orange edging in winter. Then they switch to bluish-green with white edging in summer.

This pest is native to western North America, but its range is expanding.

Winter phase Say stink bug (Frank Peairs, Colorado State University, Bugwood.org) CC BY 3.0

Say stink bug identification and lifecycle

These are large bugs, averaging ¾” in length. While in their green phase, adult Say stink bugs also have three light spots near where their shoulders would be, if they had shoulders. You may also see a white or pink spot just above where the wings emerge on nearly mature nymphs.

Females lay clusters of 30 or so white, barrel-shaped eggs on plant material. Those eggs hatch into nymphs. At first, those nymphs stay clustered together for a few days before dispersing in search of tender flowers and germinating seeds. They also eat young leaves. Nymphs are smaller and softer than adults and do not have wings. They go through several developmental stages, or instars, before reaching adulthood. There can be up to three generations each year, depending on the length of the growing season.

Say stink bug in summer phase (Kati Fleming) CC BY-SA 3.0

Say stink bug damage

Despite their fascinating wardrobe changes, Say stink bugs are much like other stink bugs. They emerge from leaf litter and ground cover in early spring, feeding on mallow, mustards, Russian thistle, and other favored weeds until your garden starts happening. They then move in, feeding on all those seeds you just planted. They especially like members of the grass family, which means alfalfa, barley, corn, millet, oats, rye, and wheat are all at risk, as well as your lawn. Then they go after your beets and tomatoes. Especially tomatoes.

Using piercing mouthparts to suck the juices from your plants, Say stink bugs may also introduce yeasts that cause fruits to rot.

​Say stink bug management

Removing weeds is one way to make your garden less inviting to Say stink bugs. Avoiding the use of broad-spectrum pesticides will encourage beneficial parasitic wasps and tachinid flies. And, as much as I dislike pill bugs, they do eat stink bugs eggs. At the end of autumn, remove over-wintering sites by composting leaf litter and other dead plant material, rather than leaving them in place.

Have you seen Say stink bugs in your garden? Let us know in the comments!