Analysis of grasshopper (Orthoptera: Acrididae) population surveys in Saskatchewan: 1972–2004

Abstract

AbstractGrasshopper population forecasting and monitoring methods in western Canada have traditionally been linked to pest control decisions primarily by providing warnings of the likelihood of crop damage. Risk to crops is categorized as very light (1–4 grasshoppers/m2), light (>4–8 grasshoppers/m2), moderate (>8–12 grasshoppers/m2), severe (>12–24 grasshoppers/m2), or very severe (>24 grasshoppers/m2). A summary of grasshopper infestation by risk category indicated that in 29 of 33 years, infestations warranted ratings of severe or very severe, with the majority of these infestations occurring in the 1980s. Infestations involving the two categories severe and very severe encompassed about 84 900 and 85 600 km2 of agricultural land during the two largest infestations in 1985 and 2002, respectively. Keeping grasshopper populations below economic thresholds through preventative measures is the goal of integrated pest management. To determine when control measures are warranted, producers are asked to monitor grasshopper populations and estimate the number of grasshoppers per square metre. Economic thresholds provide guidance in making a decision as to whether control is warranted in different crops. Using economic thresholds as a guide, this study identified the eco-districts most at risk of crop damage within each of four major eco-regions of Saskatchewan. Overall, risk was highest in five eco-districts of the Mixed Grassland Eco-region. These findings provide guidance for the agriculture industry in relation to grasshopper management and for future survey programs in relation to targeting regions of the province most at risk from grasshoppers.