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Brown marmorated stink bug - Halyomorpha halys (Stål, 1855)

(NOT present in New Zealand)

NYMPH: Main diagnostic characters

Immature stink bugs or nymphs moult through five stages (instars) before becoming adults; the fifth stage or last instar nymph is shown below.

BODY LENGTH: About 12 mm. COLOUR: Marbled brownish black with metallic lustre; legs dark with broad pale middle band, not hairy; antennae with broad pale band across tip of segment 4 and base of segment 5. THORAX: Sides with spines. SHAPE: Broad, somewhat square.

Distribution and pest status

The Brown Marmorated Stink Bug (BMSB; Halyomorpha halys) is native to China, Japan, Korea and Taiwan. It has been accidentally introduced in the United States where it has aggressively spread and established as an agricultural pest since the mid-1990s. Populations also exist in parts of Europe and Canada. The New Zealand horticulture industry presently considers the BMSB as one of the top pests of concern.

This insect is tree-loving although it has hundreds of host plants, primarily fruit trees and woody ornamentals but also field crops. Almost any crop can be at risk, including: citrus; pipfruit; stonefruit; berries; grapes; asparagus; soybeans; maize; honeysuckle; maple; butterfly bush; cypress, hibiscus; and roses. BMSB damage to woody ornamentals and forest trees has been reported as cosmetic only.

BMSB adults generally feed on mature and immature fruits, while nymphs feed on leaves and stems as well as fruits. They feed by inserting their elongated, tube-like sucking mouthparts (rostrum or beak) into plant tissue from which they suck fluids containing sugars and nutrients. This disfigures fruit and renders them unmarketable, which results in control costs and production losses.

In North America BMSB spends winter in the adult stage and becomes active during the warmer sunny days of spring when adults mate and females lay their eggs (up to 400 eggs in a female’s lifetime). The nymphs go through five stages of development during the summer before becoming adults. The optimal temperature for BMSB development is 25˚C; eggs and nymphs require a temperature of 12-15˚C to develop. Development from egg to fully mature adults takes nearly two months. BMSB can have more than one generation per year under optimal climate conditions (e.g., in its native environment of southern China).

Photos of all life stages can be found on the Stop BMSB website or on the CABI website .

BMSB is not a risk to human health but it is a public nuisance, especially when it aggregates in large numbers. When disturbed or crushed this bug emits a characteristic, unpleasant and long-lasting odour that is not health threatening. 

(See also linked resources below.)

Pathways for incursion into New Zealand

BMSB adults show strong dispersal abilities; they are able to fly over the landscape, are active at night, and can be attracted to artificial light. Many pathways for incursions are linked to BMSB’s need to seek sheltered overwintering sites; adults hide in cracks/crevices in the winter months and may find their way into a range of pathway vectors, e.g., passengers/luggage, bulk freight/cargo.

BMSB can spread by getting into loaded containers for export, the most likely method of entry into New Zealand. BMSB may also disperse through the transport of personal effects and housewares, and may also find its way into luggage, wooden boxes or containers, and mail. Eggs, nymphs, and adults can be associated with a very wide range of plant material but are less likely to be associated with commercial fruit or nursery stock imports.

MPI has a number of measures in place to reduce the risk of exotic pests being introduced including requirements for importers and screening at the border. However there is no such thing as zero risk and it is possible the insect could hitch-hike its way into the country undetected.

(See also linked resources below.)

What people can do

Keep an eye out for this bug. Report findings of any suspects to MPI on 0800 80 99 66. If possible take a photograph and/or collect samples.

Further information is available from the MPI link below.