Thursday, 25 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 21, 2020, the grasshopper model estimates that hatch varies between 15.7 % at Lacombe to more than 95 % at Winnipeg and Regina (Table 1).  The prairie average is 71 % (34 % last week) and well above the long term average of 25 % (10 % last week) (Fig. 1).  Across the prairies, populations are predicted to be 22, 20, 29, 24 and 5 % in egg, first, second, third, and fourth instars, respectively (Table 1).  Warmer conditions across southern regions of the prairies should result in rapid development of first and second instar nymphs (Fig. 2).  This will result in most populations consisting of third instar nymphs within a relatively short period of time (Fig. 3).  

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 21, 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 21, 2020.
*LTN = long term climate normals, used for comparison of current year development (OBS)
Figure 2. Predicted grasshopper (Melanoplus sanguinipes) development across
the Canadian prairies (as of June 21, 2020). 

Figure 3. Predicted percent of grasshopper (Melanoplus sanguinipes) population at third instar stage across
the Canadian prairies (as of June 21, 2020). 

The two graphs below compare grasshopper development at Saskatoon and Winnipeg.  Though both locations are predicted to have first to fourth instar nymphs, grasshopper populations near Saskatoon are expected to be predominantly in the first instar and populations near Winnipeg may consist mostly of third instars. 

Figure 4. Predicted grasshopper (Melanuplus sanguinipes) phenology at Saskatoon SK.
Values are based on model simulations (April 1-June 21, 2020).

Figure 5. Predicted grasshopper (Melanuplus sanguinipes) phenology at Winnipeg MB.
Values are based on model simulations (April 1-June 21, 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.