Grasshoppers in S.D. Rangelands
There are several species of grasshoppers that can negatively affect rangeland conditions in South Dakota. Grasshoppers tend to be more serious than other rangeland insect pests, and they occur most frequently. Each summer, the United States Department of Agriculture’s (USDA) Animal Plant Health Inspection Service (APHIS) conducts surveys throughout the Western counties to monitor grasshopper population densities. These surveys focus on collecting adult grasshoppers, and the data can be used as a prediction of areas where grasshoppers may be an issue during the following year.
When compared to data from previous years, it appears that the 2016 grasshopper populations are as severe as those observed in 2015. However, it is important to note that some of the areas with abundant grasshopper populations in 2015 were not surveyed in 2016. For 2016, the largest populations of grasshoppers were observed in Gregory, Dewey, Ziebach, Jackson, Bennett and Oglala Lakota counties (Figure 1). Although grasshopper populations appear to be lower in 2016 when compared to 2015, there were numerous reports of grasshopper populations that required insecticide management (Figure 1, Figure 2). In 2014, grasshopper populations were at a 25-year low (Figure 3).
Figure 1. 2016 Survey: S.D. adult grasshopper densities.
Courtesy: USDA APHIS
Fig 2. 2015 Survey: S.D. adult grasshopper densities.
Courtesy: USDA APHIS
Fig 3. 2014 Survey: S.D. adult grasshopper densities.
Courtesy: USDA APHIS.
Some of the factors that contribute to increased grasshopper populations include rainfall, ground cover, and variation in seasonal temperatures. Populations of grasshoppers are typically more of an issue during years when grass is stressed by drought. Long, warm falls similar to what was observed in 2016 allow for a longer period of activity for the adult grasshoppers, which can lead to an increased amount of laid eggs (Figure 4). Although the data is only collected for Western South Dakota, similar populations may be also be expected in eastern South Dakota rangeland.
Figure 4. Departure from normal temperature from Sept. 1 to Nov. 30, 2016.
- APHIS. Grasshoppers and Mormon Crickets. 2010. USDA APHIS Factsheet.
- Mesmen, A. 2015. 2015 Rangeland Grasshopper Survey. USDA APHIS.