Gesundheit für Mensch, Tier & Pflanze

Southern green stink bug

Nezara viridula

Profile

The green rice bug is a bug that mainly attacks legumes, but also numerous vegetable, fruit and arable crops, as well as ornamental shrubs and plants. It causes sucking damage to fruits, resulting in mottling, corking and deformation.

Appearance

The green rice bug belongs to the family of tree bugs and is about 14-16 mm long, 8 mm wide and mostly green in color, although other color forms (including red, orange) exist.

It looks very similar to the green stink bug(Palomena prasina), but the green rice bug can be easily distinguished from the green stink bug by the white row of dots on the lower end of the neck shield and the brightly colored transparent part of the wings.

Biology

The females of the green rice bug lay their first yellowish and later red colored eggs in clutches on the underside of the leaf. The larvae that hatch from these eggs pass through five, very variably colored stages. They usually stay in groups on the plants, where they suck mainly on fruits, but also on leaves, just like the adults.

In autumn they leave their host plants to look for overwintering quarters (e.g. ground litter, buildings). In Europe, only one to a maximum of four (in warmer areas) generations are formed. In regions with an average temperature below 5 °C in January and an average lowest annual temperature below -3 °C, the green rice bug cannot survive the winter.

Damage symptoms

The green rice bug causes sucking damage to fruits of a wide variety of plants. As a plant sucker, it is able to pierce plant tissue of fruits, seeds, leaves and shoots with its proboscis to feed on the plant sap. This sucking action causes staining, corking and deformation. Fruits become unsightly, may drop prematurely and are no longer marketable.

In addition, taste impairments are caused by the secretion of an unpleasant-smelling secretion. The puncture sites can serve as entry ports for other pests.

Host plants

The green rice bug can feed on a wide variety of plant species from all cultivated areas. Its main host plants are legumes (including soybean), but it also likes to visit vegetable, fruit and arable crops as well as ornamental shrubs and plants. Annual, herbaceous crops in particular are attacked especially at the time of fruit and seed formation.

Distribution

In Europe, the green rice bug was initially distributed only in the Mediterranean region. However, due to climate warming, it is increasingly spreading towards the north. Until 2015, only individual animals could be detected in Austria. Since then, however, numerous larvae and adults have been detected in home gardens and glass houses, especially in urban regions (Vienna and Graz), indicating temporary reproduction of the bugs.

So far, no economically relevant damage to outdoor crops has been recorded in Austria, but the green rice bug has appeared more frequently in urban allotments and community gardens in recent years (late summer). The green rice bug has also caused damage to vegetables in protected cultivation.

The mortality rate of the animals in winter has so far prevented a permanent existence of the bug populations in Austria, however, due to the increasingly milder winters, the further development of the species must be observed. Furthermore, successful overwintering in protected areas (for example, construction parts in heated glass houses) cannot be ruled out.

Strong reproduction can be observed in years with dry-hot summer conditions.

Prevention and control

  • Regular plant inspections to detect affected individual plants as early as possible and to remove eggs or larvae by collecting them.
  • To prevent the bugs from flying into the greenhouse, close-meshed (1-1.5 mm) insect screens can be attached to the vents.
  • Egg parasitoids (ichneumon wasp Trissolcus basalis) and endoparasites (caterpillar fly Trichopoda pennipes) are described as natural antagonists. However, these are not commercially available in Austria.
  • Direct control with approved insecticides against sucking insects is possible, but difficult because usually no sufficient effect can be achieved against the adult bugs.

Links

Informationen des CABI invasive species compendium: Datasheet Nezara viridula

Informationen des LTZ Augustenberg

Last updated: 23.11.2021

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