Stink bugs
Pentatomidae — chiefly Halyomorpha halys
also called Brown marmorated stink bug, Shield bugs
Shield-shaped bugs that stab fruit and pods, leaving corky dimples and cloudy spots. Exclude them with mesh while fruit is sizing and seal the house against the autumn invasion.
How to know it
A shield outline 14–17 mm long, mottled gray-brown, with alternating pale and dark bands along the abdominal margin and two white bands on each antenna — that last detail separates the invasive brown marmorated bug from the harmless natives. Green stink bugs are the same shape in plain apple green. Nymphs are rounder and boldly marked in orange and black.
What you'll see
- Corky, sunken dimples in tomato and pepper shoulders, pale and hard under the skin.
- Cloudy white spots just beneath the tomato skin, invisible until you slice it.
- Bean and okra pods pitted and puckered, with flat, shrivelled seeds inside.
- Cat-faced, misshapen apples and peaches with a corky pocket at each feeding point.
- Bugs congregating on warm south walls in October, then indoors at the windows.
Where it comes from
Adults overwinter in shelter — under bark, in wall cavities, indoors — and emerge in spring to lay barrel-shaped eggs in rafts of about 28 on leaf undersides. One to two generations a year depending on the summer, with the second peaking exactly when tomatoes and tree fruit are ripening.
A landscape pest before it is a garden pest: numbers build in woodland edges, hedgerows and field crops, then move into the garden when those dry off in late summer. Warm autumns and mild winters lift the following year sharply.
Dealing with it
- Net or bag ripening fruit clusters — exclusion is the only thing that reliably works.
- Hand-pick into soapy water at dawn; they drop rather than fly when the air is cold.
- Do not squash them indoors, and vacuum with a bag you can throw away outside.
- Skip broad-spectrum sprays: they kill the parasitic wasps that are slowly catching up with this insect and rarely reach the bug itself.
- Harvest tomatoes at first blush and ripen them on a windowsill during the worst weeks.
Keeping it out
- Seal gaps around window frames, soffits and vents in September, before the aggregation begins.
- Grow a sacrificial row of sunflowers or sorghum at the garden edge and clear the bugs off it.
- Cut back long grass and brush at the boundary in late summer, which is where the migration stages.
- Leave the native predatory stink bugs and the tiny samurai wasp alone — they are the long answer.
- Pick fruit promptly; a garden of over-ripe tomatoes is what pulls the second generation in.
What it goes for
Tomatoes, peppers, beans, okra and sweetcorn; apples, peaches and raspberries among the fruit.
Who hunts it for you
- Garden birdsPasseriformes Both things are true: birds strip your currants and a brood of blue tits takes several thousand caterpillars out of one fruit tree in a fortnight. Net what you must and welcome them everywhere else — a nest box near the apples is worth more than a spray. Grow to recruit it: Echinacea,Elderberry,English holly,Goldenrod,Rudbeckia,Sunflower
- Parasitic waspsBraconidae & Trichogramma Tiny, stingless wasps that lay eggs in or on caterpillars, aphids, and moth eggs — the white cocoons riding a hornworm are their calling card, so leave that caterpillar be. Umbel flowers with shallow nectar keep the adults fuelled. Grow to recruit it: Cilantro,Dill,Fennel,Lovage,Parsley,Sweet alyssum
- Praying mantisMantidae A sit-and-wait ambusher that snatches caterpillars, beetles, and anything else that wanders close — friend and foe alike, so count it a mixed blessing. Tall, structured plantings give it perches and egg-case anchors. Grow to recruit it: Cosmos,Fennel,Sunflower
- Tachinid flyTachinidae Bristly, house-fly-lookalike parasitoids that lay eggs on caterpillars, beetle grubs, and earwigs — the maggot consumes the host from within. Adults sip nectar from shallow umbels and daisies. Grow to recruit it: Cilantro,Dill,Feverfew,Parsley,Sweet alyssum
See also
The Cottage Garden Companion — the gardener's bestiary at cottagegardencompanion.com