Stink Bug

Halyomorpha halys / Nezara viridula

Stink bugs (family Pentatomidae) are shield-shaped insects that feed by piercing plant tissue and injecting digestive saliva that causes localised necrosis. Halyomorpha halys (brown marmorated stink bug) is an invasive species from Asia that has spread worldwide. Nezara viridula (green stink bug) is a common agricultural pest. Both emit a pungent defensive odour when threatened, giving the group their common name. They are primarily outdoor pests but can move indoors when houseplants are kept on patios or balconies.

MonsteraFiddle Leaf FigPhilodendronCalatheaPeace Lily

How to Identify

Shield-shaped insects 14–17 mm long. Halyomorpha halys is mottled brown. Nezara viridula is bright green. Adults and nymphs pierce plant tissue leaving sunken, discoloured spots (light green, yellow, or brown) surrounded by a water-soaked halo. Green shield bugs (Palomena prasina) are similar and cause comparable damage. The distinctive odour when disturbed is a reliable identifier.

Life Cycle

Females lay barrel-shaped eggs in neat clusters of 20–30 on leaf undersides. Nymphs pass through 5 instars over 4–6 weeks. Adults overwinter and re-emerge in spring. One to two generations per year depending on climate. Adults aggregate in sheltered sites for winter, sometimes entering buildings in large numbers.

Visual Identification

Brown Stink Bug

Green Stink Bug

Egg Mass Hatching

Treatment Steps

1
Hand-pick adults and nymphs into soapy water — wear gloves to avoid the odour
2
Apply pyrethrin spray to affected foliage for quick knockdown
3
Remove and dispose of egg masses found on leaf undersides
4
For outdoor plants, kaolin clay spray creates a physical barrier that deters feeding
5
Introduce Trissolcus japonicus parasitic wasps where available — specific to Halyomorpha halys eggs

Prevention

Inspect plants brought in from outdoors for egg masses on leaf undersides
Fine insect netting on outdoor plants prevents adult access
Seal cracks and gaps in window frames to prevent overwinter entry into buildings
Yellow sticky traps can capture nymphs and monitor population levels

Frequently Asked Questions

How do I know if I have stink bugs on my plants?

Look for sunken, discoloured spots on leaves and fruit surrounded by a water-soaked halo. Shield-shaped insects (brown or green, 14–17 mm) on stems and leaves, and a pungent smell when they are disturbed, are definitive identifiers.

Are stink bugs harmful to houseplants?

Stink bugs cause necrotic feeding damage where they pierce tissue, resulting in discoloured spots and distorted growth. They rarely cause severe damage to established houseplants but can be significant on fruits and vegetables.