Bathycoelia distincta (previously known as B. natalicola)
Common names: Sting bugs
Family: Pentatomidae
The two-spotted stink bug is an indigenous African species, well known from macadamia orchards in East and southern Africa. In South Africa, it was first detected in 1984 in the Levubu valley in the north-eastern part of the country, and it remains a major, well-established pest of macadamia in Mpumalanga, Limpopo, and KwaZulu-Natal, with activity occurring throughout the growing season rather than in a single defined outbreak period.
Egg: Eggs are pale greenish, turning white before hatching, and are laid in clusters on leaves or stems.
Nymph: Development passes through five nymphal stages. Early instars are creamy-white to light orange with dark blue and reddish markings on the abdomen and thorax, gradually becoming predominantly light green as they mature, with the final instar showing more developed wing pads.
Adult: Adults are green shield-shaped bugs, closely resembling the related yellow-spotted stink bug (B. rohaini), which is occasionally found on the same crops. The two species can be told apart by the colour of the spot at each front corner of the scutellum: yellow in the yellow-spotted stink bug, white in the two-spotted stink bug.
Freshly hatched first-instar nymphs of the two-spotted stink bug, aggregated around an egg mass on a tree branch. Early instars remain clustered near the eggs before dispersing to feed. – Natasha Bouwer
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Late-instar nymph of the two-spotted stink bug, showing the characteristic green coloration and developing wing pads typical of immature stages. – Natasha Bouwer
Macadamia is the primary economic host, though the bug is also recorded on avocado and pecan, as well as on wild hosts such as tassel berry and kei apple.
Feeding damage differs depending on the developmental stage of the nut at the time of attack. Feeding during early kernel development, while cell division and enlargement are still active, produces deep necrotic lesions within the kernel. Feeding after this stage tends to leave nuts with an oily, glazed, semi-transparent appearance instead. Because the bug feeds by piercing the developing nut with needle-like mouthparts, damage is often invisible from the outside and only becomes obvious once the shell is cracked or the kernel is processed, making this an economically costly pest to detect and manage. In South Africa, stink bug damage in macadamia has been estimated to cost the industry tens of millions of rand annually.
Because feeding damage is internal and easy to miss, management has traditionally relied on scheduled, calendar-based insecticide applications timed to periods of highest population pressure, guided by regular scouting of orchards for nymphs and adults. Because reliance on fixed spray calendars can lead to unnecessary applications, growers are increasingly encouraged to combine scouting data with weather and phenology information to refine timing.
No commercially available species-specific pheromone lure currently exists for the two-spotted stink bug, so management continues to rely mainly on regular field scouting combined with well-timed insecticide applications; growers should consult Insect Science directly, as semiochemical-based monitoring tools for pentatomid stink bugs are an active area of research and development.
