Grasshoppers In South Dakota Crops

 

 

 

 

Grasshoppers are insect pests that tend to flourish during dry conditions. Large grasshopper populations are being observed in field crops, particularly in areas of South Dakota that have experienced abnormally dry conditions this season (Figure 1). These large populations are partially caused by the warm, dry fall in 2015, which promoted increased grasshopper egg laying. In addition, the limited rainfall during spring and summer 2016 increased survival of grasshopper nymphs and adults. Although large populations of grasshoppers may be observed, scouting is still necessary to determine if the grasshopper population or the level of defoliation warrants insecticide management. 

 

 

There are several species of grasshoppers in South Dakota, and the species observed can vary depending on the region. The most commonly observed grasshoppers in corn and soybean fields are the differential grasshopper, redlegged grasshopper, and twostriped grasshopper. These three species can be identified from one another based on some key characteristics.

 

 

Differential grasshopper adults are large and yellow with black markings (chevrons) on their hind legs (Figure 2). Nymphs of differential grasshoppers vary greatly depending on their present growth stage (instar). As nymphs develop, they will have a black line present on their hind legs that eventually begins to resemble the black chevrons present on the adults.

 

 

 

Redlegged grasshopper adults are smaller in size than the differential grasshopper. Redlegged grasshoppers can be identified by their yellow underside and bright red legs (Figure 3). Redlegged grasshopper nymphs have distinct yellow and black markings during development.

 

 

 

The twostriped grasshopper adults are similar in size to the differential grasshopper and can be identified by the distinctive light yellow stripes that start at the head and come together on the top of the leathery front wings (Figure 4). Two-striped grasshopper nymphs generally have black spots present on their head and thorax. Nymphs also have a dark band present on their hind legs.