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Kudzu Bug (Bean Plataspid)

Author: Scott D. Stewart

Classification and Description: The kudzu bug (Megacopta cribraria) is a hemipteran insect in the family Plataspididae. Other common names include bean plataspid, lablab bug, or globular stink bug. Both immatures (nymphs) and adults have piercing-sucking mouthparts. Adults are olive green to brown in color, somewhat round, almost square in shape, and less than ¼-inch long (4 – 6 mm). Nymphs are roughly the same shape as adults but vary in color, color patterns, and number of body segments. Unlike the adults, nymphs also have hairs (setae) on their bodies. Both nymphs and adults produce an offensive odor similar to that of many stink bugs when they are disturbed. Eggs are laid in a mass of two rows, typically with 10-40 eggs per cluster. Females deposit particles containing symbiotic bacteria on the underside of eggs masses. Freshly hatched nymphs ingest these symbiotic bacteria which aid in the digestive process.

Hosts, Life History, and Distribution: Kudzu bugs are an invasive pest originating from Asia. They were first discovered in Georgia in 2009, and its distribution has rapidly grown to include most of the Southeast and parts of the Mid South. As the name implies, kudzu is an important host of this insect. Soybean and wisteria are also preferred hosts. Other members of the legume family are also hosts, but kudzu and soybean are the primary reproductive hosts for this pest. This insect is expected to spread across much of the southern one-half of the United States, particularly in areas where kudzu or soybean are common.

Kudzu bugs have two generations per year in the South. The first generation often occurs on kudzu, but may occur on soybean. The second generation begins in midsummer and may occur on kudzu or soybean or other alternate hosts. They are strong fliers with peaks in migration in the spring when emerging from hibernation, in midsummer as the second generation begins, and during the fall when seeking overwintering habitats. They are excellent hitchhikers and are often transported in vehicles, trailers, or railroad cars.

Pest Status and Injury: Kudzu bugs primarily feed on the stems of plants, removing plant juices (phloem). Thus, they can reduce the vigor of both kudzu and soybean, particularly when plants are already under stress. Infestations in soybean, at least initially, are often concentrated on field edges. It takes many kudzu bugs to cause economic damage to soybean. However, populations can reach several dozens or hundreds of insects per plant. Even though they are indirect pests, not feeding on the seeds of soybean, reported yield losses from unmanaged infestations have reached 70%.

Kudzu bugs are also a nuisance pest, invading homes during the fall for overwintering. They are particularly attracted to white or light-colored structures. Compounding this problem, the invading adults give off an offensive odor and may stain surfaces when disturbed. Other overwintering sites may include any protected cracks or crevices where the adults can aggregate such as behind tree bark.

Management Considerations: It is unclear how quickly and to what extent kudzu bugs will become an economic pest of soybean in the primary production areas of Tennessee. It is likely that many fields will require treatment annually once this pest becomes widely established. Fortunately, kudzu bugs are not difficult to control with insecticides, and research in the Southeast indicates that one well-timed application is typically sufficient to prevent yield loss. Unfortunately, infestations may occur before other pests are present in treatable numbers. Thus, additional insecticide applications may be needed and could disrupt populations of beneficial insects. This may create secondary pest problems with pests such as corn earworm or loopers.

Experience in the Southeast also indicates that many growers apply insecticides too quickly as adults are still migrating into soybean fields, resulting in an unnecessary second spray. Sampling is based on visual examination of plants or by using a sweep net. Thresholds are evolving as we gain experience with this invasive insect. Current recommendations are to treat before bloom (R1) when 5 or more kudzu bugs are present per plant. From R1 to beginning maturity (R7), treatment is recommended when an average of 1 or more immature kudzu bugs are found per sweep (i.e., 25 or more nymphs per 25 sweeps). Edge sprays may only be needed if infestations are mostly confined to field borders. Insecticide recommendations are listed in the Tennessee Insect Control Recommendations for Field Crops (PB 1768)

Reference: KudzuBug.org (www.kudzubug.org). Developed by the University of Georgia, Center for Invasive Species and Ecosystem Health.

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