Predicted grasshopper development (July 5, 2019; Wk 13)

Grasshopper Simulation Model Output – The grasshopper simulation model will be used to monitor grasshopper development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of grasshopper development stages based on biological parameters for Melanoplus sanguinipes (Migratory grasshopper).

Recent cool conditions have resulted in reduced grasshopper development rates. Based on model runs, approximately 22% (33% last week) of the population is in the first instar, 29% (26% last week) is predicted to be in the second instar, and 27% (11% last week) in the third instar, 8.2% (1.5% last week) are predicted to be in the fourth instar and less than 1% may be in the fifth instar (Fig. 1).  Grasshopper development this season has been similar to long term average development. The following map indicates that grasshopper populations across the southern prairie are mostly in the second instar with some areas having populations that are mostly third instars.

Figure 1. Predicted development stages of grasshopper (Melanoplus sanguinipes) populations across

the Canadian prairies (as of July 1, 2019). 

Biological and monitoring information related to grasshoppers in field crops is posted by Manitoba Agriculture, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture and the Prairie Pest Monitoring Network.  Also refer to the grasshopper pages within the "Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide" which is available as a free downloadable document in either an English-enhanced or French-enhanced version.