Megacopta cribraria

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Taxonomy
Kingdom: Animalia
Phylum: Arthropoda
Class: Hexapoda (including Insecta)
Order: Hemiptera
Family: Plataspidae
Genus: Megacopta
Species: cribraria
Scientific Name
Megacopta cribraria
(Fabricius)
Common Names

kudzu bug, bean plataspid, lablab bug, globular stink bug, kudzubug


Overview

Kudzu bug was found in the United States in October of 2009. Since then, it has spread through out the southeast. Where it has spread, it has become a nuisance pest as adults look to overwinter in buildings and a new pest of soybean.

Identification

Adults

Adults are 3.5 to 6 mm long, oblong, olive-green colored with brown speckles, and produce a mildly offensive odor when disturbed. In the United States, characteristics of the adult kudzu bug useful in distinguishing it from other stink bugs (Pentatomoidea) include: the plate in the center of its back (the scutellum) is broader along the bottom than it is along the top, and much wider than it is long. There also appears to be a seam (pseudosuture) running lengthwise down the center of the plate. The tips of the legs furthest from the body (tarsi) are 2-segmented. The kudzu bug has a round body shape rather than the triangular to semi-elliptical body shape of other stink bugs as well as a distinctive head shape. The size of the kudzu bug ranges from a sixth to a quarter inch (3.5 to 6 mm long). Finally, the second antennal segment is shorter than that of most other stink bugs.

Dorsal view of Megacopta cribraria adult
Ventral view of male adult

Eggs and Nymphs

Adult females deposit small brownish particles on the underside of their egg mass. These unique structures are symbiont capsules which contain specific symbiotic bacteria inside. Newborn nymphs ingest content of the symbiont capsules, and the symbiont is thus transmitted from the adult females to their progeny immediately before and after birth.

Nymphs are the immature forms of the kudzu bug which hatch from the eggs. Unlike a larva, the overall body form of a nymph resembles that of an adult, but sexual maturity is not reached until it has shed its exoskeleton several times and gone through several developmental stages known as instars. Differences between instars can often be seen in altered body proportions, colors, patterns, or changes in the number of body segments.

Megacopta cribraria eggs; symbiont capsules are indicated by red arrows
Underside of Megacopta cribraria eggs
Newly hatched first instar nymphs
Third instar nymph
Fourth instar nymph
Fifth instar nymph

Look-alikes

Megacopta and Symphylus

The difference between the shields of these two different genera can prove useful for identification. Symphylus species are referred to as shield-backed bugs because the area where the wings and legs attach (thorax) is enlarged and forms a continuous shield over the abdomen and wings. This distinguishes the shield-backed bugs from most other “true bugs” (Heteroptera), but the kudzu bug has a shield as well. To distinguish between the two genera, note that the end opposite the head (posterior) of a Symphylus species is rounded, but that of the kudzu bug (Megacopta species) is cut short, or truncated.

Megacopta cribraria is truncate posteriorly as indicated by the red arrow
Symphylus species are rounded posteriorly as indicated by the red arrow

Megacopta and Diolcus

There are two ways to distinguish the kudzu bug from Diolcus species (shield-backed bugs). The head's lateral lobes (left and right sides) of Diolcus are separated, but in species of Megacopta, these lobes are contiguous and touch along a boundary at the nose end. The second difference is the longer antennal second segment of Diolcus species.

Megacopta cribraria; red arrows on left and right indicate contiguous juga and a shorter antennal second segment, respectively
Diolcus species; red arrows on left and right indicate longer antennal second segment and separate juga, respectively

Kudzu Bug and Other Shield Bugs

The kudzu bug differs from other shield bugs (Plataspidae) by the following:

  • Relatively uniform coloration on its back.
Megacopta cribraria, the kudzu bug, belongs to the family Plataspidae
A shield bug of the family Plataspidae
A shield bug of the family Plataspidae
A shield bug of the family Plataspidae
  • The upper surface of the tibiae has grooves for the entire length.
  • Distinctive coloration on its underside. The underside of the female kudzu bug has broad pale areas running down the length of its sides. The underside of the male kudzu bug also has broad pales areas on its sides, but they are restricted to two subunits of the exoskeleton below the bottom legs.
Ventral view of female kudzu bug; red arrows indicate characteristic broad lateral pale areas
Ventral view of male kudzu bug; red arrows indicate characteristic broad lateral pale area restricted to visible abdominal sternites 2 and 3

Hosts

Kudzu, soybean, wisteria, and several other legumes have been reported as hosts.

Distribution and spread

This insect is native to Asia. It was first reporteed in the United States in October of 2009, Beginning in Georgia, this pest as spread quickly throughout the southeast. All counties of South Carolina, as well as many counties of North Carolina and Georgia have reported finds. Only a few counties in Virginia and Alabama have reported infestations. Any new reports whould be sent to Dr. Wayne Gardner.

Data provided by: Megacopta Working Group.

Behavior[1]

Overwintering adults become active in the springtime. They will feed and reproduce primarily in kudzu, starting a new generation or cycle of the insect. Unfortunately, many of the adults produced in this new generation move over onto soybeans in June and July where they become an economic problem.

In most of Georgia, these insects develop a second generation during the summer growing season. This results in a larger fall population and nuisance activity for homeowners and outdoor activities. Based on what we know about other insects, scientists currently believe that a combination of day length, change in plant (kudzu) physiology, dying host plants, and perhaps declining temperatures trigger kudzu bugs to leave their kudzu host in search of protected sites where they will spend the winter. Overwintering sites are any crack or crevice where a group of bugs can aggregate. For example, this can be, but is not limited to, the gaps under the bark of trees or under the siding of a home. They seem to like high places as well, such as the edges of homes (fascia boards, gutters). At any rate, during each of the past several years, this fall flight began in mid-October and did not subside until late November or early December.

Kudzu bugs are attracted to light-colored surfaces, especially white (e.g., siding of homes, white shirts, white cars, etc.). When large numbers of bugs are present, it is not uncommon to find them on most types of vegetation, including oak and pine trees, tomato plants, azaleas, etc. They are not reproducing on these plants. Kudzu bugs only reproduce on plants known as legumes. In the fall, kudzu bugs fly to homes and are a general nuisance due to their large numbers. On homes they aggregate in large numbers. During cool, fall mornings they are not very active, but when temperatures warm into the afternoon their flying and nuisance activity increases dramatically. Those planning outdoor activities should take this observation into account and, if needed, plan outdoor activities for the morning.

Management

Exclusion

Sealing all cracks and crevices around homes, installing or repaining window screens, and making sure that door sweeps function properly can help keep the adults from entering buildings. It is bes to do this in late summer before the fall flight of the adults.

Physical Removal

The bugs can be picked up with a vacuum if they enter a building. It is best to avoid crushing them or using a vacuum that will push them through the motor since they can produce foul smells, the resulting 'bug goo' can leave stains, and some people may have an alergic reaction if they come in contact with the ground bug parts. A stocking or pantyhose placed in the vacuum tube and secured to the end of the tube with a rubber band can help by catching the insects before they reach the motor of the vacuum.

Host Removal

Removal of kudzu or other host material from around the house can limit the number of bugs that may try to enter the building.

Chemical Control

When outdoors, bugs on the building may be sprayed directly with a pyrethroid insecticide. Do not spray indoors or anywhere close to a body of water. Prior to the use of any pesticide, first read and follow the pesticide label’s directions for use on the product’s label.

Recent news

  • Dr. Tracie Jenkins says the bug most likely invaded Georgia from Japan. Prior to its discovery in Atlanta in October 2009 it was not known from this hemisphere. It made its way to the U.S. from a single introduction.
  • Dr. Jim Hanula reported that the bug is impacting Georgia kudzu by reducing growth by perhaps 30-50%.
  • Dr. Phillip Roberts reports that the bug is having an impact on Georgia soybean by reducing yield by around 20%.
  • Dr. John Ruberson reports that here in Georgia there does not appear to be very many native natural enemies of kudzu bugs. As a result, he and scientists at the USDA-ARS have searched for and identified a parasitoid in Japan. Plans are to import and release, in Georgia, this minute wasp for biological control purposes. The wasp parasitizes kudzu bug eggs.

Who to Notify

  • In Georgia
Control of Nuisance Kudzu Bugs in the Urban and Suburban Home Environment
Contact Dr. Dan Suiter in Griffin
Control of Kudzu Bugs in Soybean
Contact Dr. Phillip Roberts in Tifton.
Control in Kudzu Bugs in Backyard Vegetable Gardens (including organically-grown beans)
Contact Dr. Stormy Sparks in Tifton.

Images




Resources

References

  1. Kudzu Bug Update: March 2012. Dan Suiter and the UGA CAES Megacopta Working Group
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