Green vegetable stink bug

Nezara viridula (L.)

Heteroptera: Pentatomidae

The green vegetable stink bug (Australia, New Zealand) or Southern green stink bug (USA) is probably native to the Ethiopian region, but now dispread widely throughout the tropics and subtropics. Its omnivorous feeding habit makes it an important pest on many vegetable crops in Asia, Africa, North- and South America as well as Australia and Europe

Host plants and damage

Green vegetable stink bug is polyphagous and attacks many species of Leguminouse, Cruciferae, and Solanaceae. However, the species does not reproduce on all hosts. Favorite host plant is soybean. Green vegetable stink bug attack affects pod development, increases pod fall, and reduces the number of seed per pod in soybean.

Green vegetable stink bug feeds primarily on fruiting structures and growing shoots. They pierce plant tissues and insert saliva to liquefy plant tissue. The liquefied food is sucked up. Piercing forms after a while brown or black spots on the plant.

Feeding punctures provide access for infection by bacteria and fungus. This species is known to transmit Nematospora ssp., which cause rotting in cotton and beans. It also transmits tomato bacterial spot.

Morphology & biology

Stink bugs can be distinguished by most other bugs through there triangular scutellum which is longer than half the length of the abdomen. The green vegetable stink bug should not be confused with the green stink bug, Nezara hilaris Say, which has a more northern distribution.

Species in the genus Nezara vary in color, but green is predominant. Adults lay batches of eggs, ranging from 30-130 eggs, under leaves or fruiting structures of host plants. Eggs are white to light yellow in color and barrel shaped with a flat top. They are glued together and to the substrate. Eggs hatch after 4-9 days. Newly hatched species are red in color and stay for two days or longer on the egg mass. First instar nymphs do not feed. The first three instars form clusters, but individuals disperse when disturbed. Fourth and fifth instar nymphs do not aggregate. Last instar nymphs are sensitive to day length, which along with temperature determines entry into adult diapause.

Adults are large, shied shaped, green bugs, 8 x 15 mm in size. Small black spots can be found at the sides of the abdomen. The wings completely cover the abdomen. Adult green vegetable stink bugs can fly strongly. The life-cycle duration depends on temperature and nutrition.

N-tridecane plays a role in aggregation of early instar nymphs, whereas in adults it serves as an alarm pheromone against predators.

Monitoring

Because early nymphal stages are clustered, appropriate sampling patterns must be used to monitor presence and abundance. Simple methods like net sweeping within grids remain the most reliable methods. Searching for eggs and damage is labor intensive and unreliable because they are not readily detected.

Pest management

Over 80 parasitoids of the green vegetable stink bug are known. There have been a number of successes with biological control of the green vegetable bug, particularly with the egg parasitoid Trissolcus basalis. In Hawaii, the introduced parasites T. basalis, Trichopoda pilipes, and Trichopoda pennipes have become established. T. basalis contributes in Australia to the control of green vegetable stink bugs.

T. pennipes and T. pilipes are flies parasitizing adult green stink bugs. T. basalis is also reported as important antagonist in Brazil and Argentinia.

Other parasitoids are more sporadic and/or less abundant. Various parasitoids of eggs such as Ooencyrtus johnsoni, O. californicus, and T. urichi have been reported in several countries.

Parasites of stages other than the eggs have been used in biological control. Foremost of these are species in the family Tachinidae. For example, rates of infection by Trichopoda giacomellii as high as 53 % have been reported in soybeans from Brazil.

Cultural control

Experiments with early-maturing soybean varieties as trap crops have been reported. Insecticides should be applied to these early maturing crops before the main crop reaches pod set.

Some soybean cultivars are less damaged than others and strains that appear to have a high level of resistance are available.

Chemical Control

Carbamates and organophosphates have proven to be effective, but insecticidal plant extracts such as azadirachtin were ineffective.