Written collaboratively by Adam Varenhorst, Amanda Bachmann, Philip Rozeboom, Patrick Wagner, and Brad McManus.
Originally Submitted: July 24, 2023
While scouting soybean this week, we noticed an uptick in redheaded flea beetle activity. In soybean, redheaded flea beetles defoliate leaves but rarely cause enough defoliation that insecticidal management is necessary. In the fields that we scouted, defoliation levels were still very low at less than 5%.
Identification
Redheaded flea beetles get their name due to the distinct red-brown colored head, which stands out on their otherwise shiny black bodies (Figure 1). Flea beetles have specialized hind legs that enable them to jump long distances, similar to fleas. The redheaded flea beetle is one of the larger flea beetles that may be observed in South Dakota crops.
Scouting in Soybean
In general, flea beetles are defoliators that eat small holes into soybean leaves (Figure 2). Although these beetles are typically not a serious soybean pest, large populations can result in considerable defoliation. Since there are also other defoliating insect pests present in soybean at this time of the season, we recommend scouting and using the cumulative defoliation threshold of 20% defoliation after flowering to determine if treatment is necessary (Figure 3).
Feeding Holes
Defoliation Chart
Management
In soybean, if defoliation is greater than 20% after flowering, determine all of the defoliating species that are present and review the South Dakota Pest Management Guide: Soybean for an insecticide option that will manage all observed pests.
