Grasshopper Destruction of Rangeland Grasses

Utilization of leaf material from cool and warm season grasses by grasshoppers was determined in 1987 and 1988. The study was conducted on a Mixed Grass Prairie site in western South Dakota near the town of Belle Fourche. The principal cool season grass was western wheatgrass and the warm season grasses were blue grama and buffalograss. Utilization of these grasses was evaluated for two grasshopper species, Melanoplus sanguinipes in 1987 and Aulocara elliotti in 1988. Grasshoppers were stocked in 0.25 m2 caged plots at a rate of 20/m2 (5 per cage) for the grazing treatments. Caged plots with no grasshopper grazing were the controls. Melanoplus destroyed (consumed + waste) 24% of its body weight daily and Aulocara destroyed approximately 18%. Forage losses on rangelands having a grasshopper density of 20/m2 would be approximately 134.6 Ib/ac/month for Melanoplus and 1 17.3 Ib/ac/month for Aulocara. When calculated based on the Soil Conservation Service recommended livestock stocking rate of approximately 2.7 ac/AUM (0.37 AUM/ac), Melanoplus consumed (at a grasshopper density of 20/m2) 47% (363.6 ibl2.7 ac/month) and Aulocara 41 % (316.7 lb12.7 ac/month) of the forage required for one animal unit on 2.7 ac for 1 month