Thursday, 21 July 2016

Weekly Update (July 20, 2016; Wk 12) - Grasshoppers

Grasshoppers (Acrididae) – In central Saskatchewan, grasshopper development is currently more than 1-2 weeks ahead of average development. 

The following graph shows predicted grasshopper development at Saskatoon for July 17, 2016. The model indicates that fourth and fifth instar numbers have peaked and that adult grasshopper numbers are increasing. 

The second graph illustrates grasshopper development (for Saskatoon) based on Long Term Normal (LTN) data. Based on average weather, the population should be primarily in the fourth instar with increasing numbers of fifth instars and adults. 

Sentinel site results in Saskatchewan (July 13, 2016) indicated that the mean melanopline instar was 3.4. Melanoplus dawsoni was the dominant species (40.4%), followed by M. bivittatus (21.6%). Melanopline adults have been collected for M. dawsoni, M. bivittatus and M. sanguinipes.


The following image showing various stages of Camnulla pellucida is provided below - note that adults have wings extending the length of the abdomen whereas nymphs lack wings but develop wing buds that will eventually mature to wings.  

Figure 1. Life stages of Camnulla pellucida which including eggs, first-fifth instar nymphs and adult (L-R).

- Generally, the economic threshold for grasshoppers in cereals is 8-12 per square metre but will vary by crop and growing conditions.

Biological and monitoring information related to grasshoppers in field crops is posted by the provinces of ManitobaSaskatchewanAlbertaBritish Columbia and the Prairie Pest Monitoring Network.  Also refer to the grasshopper pages within the new "Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide" - both English-enhanced or French-enhanced versions are available.