Friday, 12 June 2020

Predicted grasshopper development

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). 

As of June 7, 2020, predicted embryonic development was 82% (78% last week) and is 6% greater than long term average values. The simulation estimates that hatch is well underway and development of nymphs was greater than average for all 8 locations that are listed in Table 1. The prairie average for nymph development is currently estimated at 20% and is well above the long term average of 4.5% (Fig. 1). Average nymph development last week was estimated to be 7%. 

Table 1.  Predictive model output estimates for Melanoplus sanguinipes development (% of total population for each location) at selected sites across the Canadian prairie as of June 7, 2020.

Figure 1. Grasshopper hatch (%) based on model simulations using current environmental conditions (blue bars) compared to long-term normal (red bars) as of June 7, 2020.
*LTN = long term climate normals, used for comparison of current year development (OBS)

Grasshopper hatch is predicted to be greatest across the southern prairies at this time (Fig. 2). Areas bound within the black line in the map illustrating hatch of the migratory grasshopper (M. sanguinipes) are areas where the predicted hatch is 35% or greater (Fig. 2).  This region includes most of south and central Saskatchewan (Fig. 2). 
Figure 2. Predicted percent of grasshopper (Melanoplus sanguinipes) population at hatching stage across
the Canadian prairies (as of June 7, 2020). 

The two graphs compare development of grasshoppers in Regina (Fig. 3) and Saskatoon (Fig. 4).  Model output indicates that 2nd instar nymphs may be present at Brandon, Lethbridge, Regina, Saskatoon and Winnipeg (Table 1). Third instar grasshoppers are predicted for Brandon, Regina and Winnipeg (Table 1).

Figure 3. Predicted grasshopper (Melanuplus sanguinipes) phenology at Regina SK.
Values are based on model simulations (April 1-June 7, 2020).

Figure 4. Predicted grasshopper (Melanuplus sanguinipes) phenology at Saskatoon SK.
Values are based on model simulations (April 1-June 7, 2020).

Biological and monitoring information related to grasshoppers in field crops is posted by Manitoba AgricultureSaskatchewan AgricultureAlberta 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" (Philip et al. 2018) as an English-enhanced or French-enhanced version.