Beware the Black Bean Bug! Florida Growers on Alert

Invasive plant pests can be discovered in a variety of ways. Awareness and a sharp eye — no matter where you’re looking — are vital. That’s especially the case in what triggered the latest Pest Alert from the Florida Department of Agriculture and Consumer Services’ Division of Plant Industry (FDACS-DPI) for the black bean bug (Brachyplatys subaeneus Westwood).

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According to the Pest Alert, UF/IFAS scientist Amanda Hodges and graduate student Adam Pitcher noticed an unusual post on iNaturalist recently and suspected a new plataspid bug in Florida. The bugs were on seagrape near the North Miami Beach boardwalk. Follow-up by FDACS-DPI Cooperative Agricultural Pest Survey Inspector Phellicia Perez revealed black bean bug.

Check out some key specs on the pest as provided by the FDACS-DPI Pest Alert.

Origin

This species is reported from much of Asia, from India in the west, to Japan and Southeast Asia in the east. It is known to be a minor pest, particularly in legume crops, but infests a wide range of plant species. Black bean bugs were found for the first time in the Western Hemisphere in Panama in 2012; however, the bug was misidentified. There are verified reports now from Panama, Costa Rica, Dominican Republic, and Ecuador.

Crops Affected

Black bean bugs can be damaging to crops and ornamental plants, especially legumes. Corn, hemp, sweet potato, potato, sugarcane, and rice (all crops grown in Florida) are reported hosts.

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Black bean bugs show a clear preference for Fabaceae, but they also are reported to damage plants in several other plant families. Important legume crop species known to be infested include common beans, cowpeas, soybean, and gandules (aka, pigeon peas).

Identification

Black bean bugs are almost entirely shiny black, with yellow markings on the face and pronotum. They have a wavy yellow line that forms a broad letter ‘W’ on the anterior part of the pronotum. The patterns on the ventral (under) side of the bug are diagnostic but differ between males and females. Adult bugs are about 5 mm long. Typically, they feed in groups on petioles or stems, similar to the kudzu bug, Florida’s only other plataspid. Kudzu bugs are mottled brown, not black, so the two plataspids will not be confused.

Black bean bugs might be confused with bugs in the family Thyreocoridae, which also are shiny black. Thyreocorids never have the diagnostic yellow W on the pronotum that is always present on black bean bugs; however, thyreocorids may have white, yellow or orange lateral markings. The head of a black bean bug is at least twice as wide as it is long and has some yellow markings. Thyreocorids never have a head that wide and usually do not have yellow markings on the head. Black bean bugs also resemble some beetles; however, black bean bugs have sucking mouth parts, and beetles never do.

If you suspect you have this bug, submit a sample to DPI for identification.

Survival and Spread

Black bean bugs suck nutrients from plants. Females produce 300 to 400 eggs, laid over a period of several months, deposited in cryptic places on or near the plants. Nymphs and adults tend to aggregate on stems or on petioles under leaves.

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