Thursday, 23 June 2016

Weekly Update (June 22, 2016; Wk 08) - Grasshoppers

Grasshoppers (Acrididae) – Previous model predictions related to hatch and nymphal instar development can be reviewed here.  

For the week of June 19, 2016, warm conditions in southeastern Saskatchewan and southern Manitoba were predicted to result in enhanced grasshopper development. Across the prairies, grasshoppers should be between the first and fifth instars. The model predicted that approximately 15% of the population was predicted to be in the first instar, 35% second, 28% third, 13% fourth instar and just under one percent fifth instar.  Development is well ahead of average rates (22% first instar, 14% second instar and 10% third instar). 

In central Saskatchewan, grasshopper development is currently more than two weeks ahead of average development. The following graph shows grasshopper development at Saskatoon based on 2016 data. The model indicates that fifth instar grasshoppers should be present.

Now compare the above with the following graph which illustrates grasshopper development (for Saskatoon) based on long term normal (LTN) data.  The model indicates that  primarily first instars are predicted to be present with only the initial appearance of third instar nymphs. 

The following image showing various stages of the clearwinged grasshopper 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).

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.