Alfalfa weevil (May 30, 2019; Wk 08)

Alfalfa Weevil (Hypera postica) – Degree-day maps of base 9°C are produced using the Harcourt/North Dakota models (Soroka et al. 2015).  Models predicting the development of Alfalfa weevil (AAW) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. 


Model runs for Brooks AB and Swift Current SK were projected to June 15, 2019.  The model runs indicate that second instar AAW should begin to appear over the next few days.  Third instar larvae are predicted to occur one week later. The warm weather over the next few days may speed up development.

Figure 1. Projected predicted status of alfalfa weevil populations near Brooks AB to June 15, 2019,using long term average temperatures.

Figure 2. Projected predicted status of alfalfa weevil populations near Swift Current SK to June 15, 2019,using long term average temperatures.

The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer”.  The green larva featuring a dorsal, white line down the length of its body has a dark brown head capsule and will grow to 9mm long.  

Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon).  Additional information can be accessed by reviewing the Alfalfa Weevil Page extracted from the "Field crop and forage pests and their natural enemies in western Canada - Identification and management field guide" (Philip et al. 2015). The guide is available in both a free English-enhanced or French-enhanced version.