Pay Extra Attention to Grasshopper Populations Back »

Figure 1. Map of South Dakota indicating where grasshopper populations were at or above thresholds. Orange shaded counties indicate that 1 out of 9 samples had threshold populations. Dark red shaded counties had at least 2 out of 9 samples that had threshold populations.

Written collaboratively by Adam Varenhorst, Amanda Bachmann, Philip Rozeboom, Patrick Wagner, and Erica Anderson.

The 2018 Eastern South Dakota grasshopper survey has indicated that there a few counties that are at an increased risk for grasshopper populations that could cause severe defoliation to current crops as well as fall emerging winter wheat. Although many areas of the eastern side of the state actually have lower grasshopper abundance than 2017, there are still hotspots. The counties where increased grasshopper abundance was observed in at least one of the nine locations sampled include Aurora, Charles Mix, Clark, Day, Edmunds, Hand, Hughes, Hyde, McPherson, Potter, Roberts, Sanborn and Sully (Figure 1, orange counties). Counties where two or more samples were observed with increased grasshopper abundance include Brule, Buffalo and Marshall (Figure 1, dark red counties).

These results indicate that even within counties there are hotspot locations. If you have crops within the indicated counties monitor them for defoliation as well as for pod feeding in soybean. Many of the increased grasshopper populations were near alfalfa fields, which may be a source. For winter wheat that is planted into the indicated counties, scouting should begin at emergence to ensure that stand reduction does not occur this fall.

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