Alfalfa Plant Bugs Showing Up in Abundance

Figure 1. Alfalfa plant bug adults and nymphs captured with a sweep net. (Credit: Adam Varenhorst, SDSU Extension)

Written collaboratively by Patrick Wagner, Adam Varenhorst, Philip Rozeboom, and Bradley McManus.

There have been several insect pests showing up in alfalfa this season, including the alfalfa plant bug. We consider the above-average spring temperatures and drought-stressed plants in eastern South Dakota to be the primary drivers of these issues. Although they typically don’t surpass economic threshold, alfalfa plant bugs have appeared in large numbers this past week while scouting alfalfa fields (Figure 1).

Profile

Alfalfa plant bug adults are approximately 3/8 of an inch long and pale green to brown in color (Figure 2). They are nearly twice the size of Lygus bugs (Figure 3), although the two can sometimes be confused. Alfalfa plant bug nymphs are small, bright green in color, and do not have fully developed wings. Alfalfa plant bugs feed on the leaves, buds, and flowers of alfalfa plants. This feeding injury can lead to stunting and reduced forage quality of the affected crop.