THE DISTRIBUTION AND ABUNDANCE OF ADULT GRASSHOPPERS (ACRIDIDAE) IN CROPS IN ALBERTA, 1918–1975

Abstract

AbstractAnnual surveys of the adults show that outbreaks of grasshoppers in cultivated crops in Alberta have occurred in 32 of 58 years. Five outbreaks have occurred, lasting from 3 to 14 years, interspersed by periods of low infestation lasting from 3 to 9 years. Some control measures, however, were required every year even during periods of low infestation. The highest recorded adult populations occurred in 1933, 1936, and 1962, and the lowest in 1952 and 1969.During most periods with low populations, infestation were confined mainly to the area south of the Bow and South Saskatchewan rivers. When high populations occurred, the infested areas increased in size and extended north to the Battle River. The largest infested area covered 48,600 sq. miles and the smallest was 300 sq. miles.Two species of grasshoppers, Camnula pellucida (Scudder) and Melanoplus sanguinipes (Fabr.), generally predominated in separate regions. Melanoplus bivittatus (Say) predominated only during periods of low grasshopper infestation. Melanoplus packardii Scudder was restricted in its range and became noticeable when the grasshopper outbreaks were declining.