Nezara viridula

Scientific Name Nezara viridula (Linnaeus)
Common Names English: Southern green stink bug; German: Grüne Reiswanze; French: Punaise verte du sud; Spanish: Chinche verde de las hortalizas
Description Adults have the typical, shield-shaped body of „true bugs“. They are 12-14 mm (0.47 - 0.55 inch) in length and about 7-8 mm (0.75 - 0.31 inch) wide. Most specimens are dull green, but other color forms exist, e.g. red-brown. The eyes are dark red or black.
The nymphs show a characteristic pattern of spots on the abdomen: the coloration of the spots changes considerably during development.
The status of the taxon N. viridula is controversial. It includes several „cryptic“ species, which might explain the contradictory evidence regarding host plants. Striking differences in host-plant relationships between its populations could be based on genetical differences, or they might just reflect varying availability of hosts.

Biology

Damage

Like all bugs, N. viridula has piercing-sucking mouthparts with which it penetrates plant tissues (preferably those of young, developing plant organs), injects saliva, and ingests the resulting liquid. The main causes of damage are the saliva, which contains toxic substances, and the direct destruction of tissues.
This damage is of two types:
if young seeds, kernels or fruits are injured, the cessation of growth around the feeding punctures leads to malformations. Fruits show „cat-facing“, and become mostly unmarketable. Seeds and kernels may stay empty, or may later fail to germinate. Blossoms fail to open and/or fall off. In rice and small grain hosts, plants become stunted because of damage to the growing points. If older fruits are attacked, the necrotic tissue will appear as a dark, hard mass that reduces quality and spoils the taste of the produce. For example, hazelnuts taste bitter when they have been punctured, even if they are otherwise intact.
The wounds left by the bug facilitate infections by fungal and bacterial pathogens, some of which may produce toxins that are harmful for humans and animals: the bug is also a vector for some of these.

Lifecycle

The overwintering adults of N. viridula emerge in the spring. After some feeding activity, mostly at night, they mate and start oviposition. Eggs are laid on the surface of the undersides of leaves in firmly glued-together clusters of about 30-130. The time until hatching may vary from 4 days to 3 weeks, depending on temperature. First-instar nymphs do not feed, but stay tightly aggregated. This behavior becomes less and less pronounced from one instar to the next. The last (fifth) instar nymphs disperse over the plant as the adults do.
The whole development cycle lasts 35-70 days. Adult females take about 3 weeks to mature, after which they are able to lay up to 250 eggs. Under favorable conditions, five generations a year are possible. Oviposition continues until early winter, when the insects hide under loose bark, in leaf litter and other places suitable for hibernation.
The adults can live for several months. When disturbed, they emit a foul-smelling liquid that consists mainly of hydroquinones. These bugs use substrate-borne vibrations for communication towards finding a mating partner.

Occurrence

Additional Crop Information

The Southern green stink bug is highly polyphagous, attacking a wide range of plants from various families, with a preference for leguminous crops.

Agricultural Importance

N. viridula is an economically-important pest in most of the areas in which it occurs, i.e. throughout the tropical and subtropical regions of all continents except Antarctica. It is a strong flier, with an ability to cover distances of many kilometres, and is still spreading to new areas.
Given its polyphagy and worldwide distribution, N. viridula is generally considered to be a very important insect pest.

Control

Integrated Crop Management

Trap crops (i.e. attractive host plants grown around fields of the actual crop) can help to intercept migrating stink bugs.

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