The Responses of Grasshoppers to Ecological Changes Produced by Agricultural Development in Southwestern Manitoba

Abstract

AbstractSouthwestern Manitoba, a semiarid area subject to periodic droughts, was originally covered by a mixed prairie on light sandy soil. Settlement commenced on the completion of the land survey in 1890. By 1913 all the land was taken up and a cereal grain economy had developed. Soil drifting became a problem and was particularly severe during the drought years of 1929 to 1934. Local species of grasshoppers, Melanoplus sanguinipes (Fabricius), Melanoplus bivittatus (Say) and Camnula pellucida (Scudder) first became pests during a minor drought in 1901 and occurred in a severe outbreak in the major drought period. Recently abandoned fields suffered severe wind erosion and drift ridges of soil provided the most favorable egg laying sites for M. sanguinipes and to a lesser extent for M. bivittatus. The effect of slope of ground on egg deposition and grasshopper behavior in relation to temperature and moisture are recorded. Succulent, introduced weeds and cereal crops supplied abundant food. C. pellucida, a grass feeder, was favored by the planting of cereal crops adjacent to egg bed sites among Carex stenophylla Wahl., and Agropyron smithii Rydb. on the roadsides. Methods of farming designed to prevent wind erosion, the use of herbicides and the grading of roadsides have shown the possibilities of ecological management to reduce grasshopper increase.