Figure 1. Redheaded flea beetle adult. Courtesy: Adam Varenhorst
This week we noticed large populations of redheaded flea beetles in soybean. These beetles get their name due to the distinct red-brown colored head, which is contrasted by their otherwise shiny black bodies (Figure 1). Furthermore, 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.
In general, flea beetles are defoliators that produce small holes in the 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 defoliating threshold of 20% to determine if treatment is necessary (Figure 3).
Figure 2. Small holes from redheaded flea beetle feeding. Courtesy: Adam Varenhorst.
Figure 3. Soybean defoliation chart. Developed by Marlin E. Rice.