Nezara viridula, commonly known as the Southern green stink bug, is a widespread insect. This species belongs to the family Pentatomidae, often recognized by the strong odor they release when disturbed. Originating in regions of Africa or the Mediterranean, it has become one of the most successful insect species across various climates. This bug is known for its broad diet and its impact on agricultural systems worldwide.
Identification and Life Cycle
The adult Southern green stink bug has a shield-shaped body, typically 15 millimeters long and 8 millimeters wide. Its coloration is usually apple-green, though some individuals may display reddish-brown variations. These color morphs are a natural part of the species’ appearance.
The life cycle begins with barrel-shaped eggs, approximately 1 millimeter high, laid in hexagonal clusters. These clusters, containing 30 to 130 eggs, are typically found on the undersides of leaves or on fruits. Initially pale yellow, eggs gradually change to a clear orange before nymphs hatch by pushing off a disc-shaped cap.
After hatching, the insect progresses through five nymphal instars, each with distinct appearances. First instar nymphs are largely black and aggregate around empty eggshells. As they develop, their coloration changes, incorporating more green. Wing pads become visible on fifth instar nymphs, indicating their nearing adult form.
Geographic Distribution and Diet
The Southern green stink bug is found globally in tropical and subtropical regions. While its precise origin is debated, it likely spread from Ethiopia or the Mediterranean basin. It is now established across the Americas, Pacific Islands, Japan, Australia, New Zealand, Africa, and increasingly found in temperate zones, particularly in greenhouses.
This insect is highly polyphagous, meaning it feeds on a vast array of plant species. Its diet includes many economically important crops, such as legumes (soybeans, beans), cotton, corn, and various fruits and vegetables. Specific examples include citrus, macadamia nuts, mangoes, peppers, tomatoes, and raspberries, demonstrating its adaptability to diverse agricultural environments.
Agricultural Impact and Damage
The Southern green stink bug damages plants using piercing-sucking mouthparts, which are needle-like stylets. These stylets penetrate plant tissues to extract sap, causing various injuries. Feeding punctures are not immediately visible but result in delayed symptoms.
Damage to fruits appears as hard, brownish or black spots, or leads to deformation, sometimes called “cat-facing.” Feeding on young shoots can cause them to wither or die, retard fruit growth, and lead to premature fruit drop. In leguminous pods, feeding can damage seeds and distort pod development. The feeding activity also creates entry points for fungal and bacterial infections, further compromising plant health.
Management and Natural Enemies
Controlling Southern green stink bug populations often involves natural enemies. A primary biological control agent is the parasitoid wasp, Trissolcus basalis, which targets the bug’s eggs. Female wasps deposit eggs inside stink bug eggs; wasp larvae develop internally, preventing the stink bug from hatching. This wasp is efficient, often parasitizing nearly all eggs within a cluster, with reported parasitization rates averaging 95 percent.
Other natural enemies include parasitic flies that lay eggs on adult stink bugs; the resulting maggots develop inside the host, causing its demise. Beyond biological control, other strategies include trap cropping, where preferred host plants like Crotalaria (rattlepod) are planted to attract the bugs away from main crops. This concentrates the pest population, making them more susceptible to natural enemies or targeted interventions, reducing their overall impact on agricultural yields.