Model simulations for alfalfa weevil (AAW) (Hypera postica) predict, as of June 13, that alfalfa weevil populations should be in the third larval instar (Fig. 1). Fourth instar larvae are predicted to occur across southeastern Saskatchewan and southern Manitoba.
The following graphs indicate that development is more advanced near Brandon (Fig. 2) than Swift Current (Fig. 3). Simulation runs indicate that by June 29, southern Manitoba populations will be in pupal stage whereas Swift Current populations are predicted to be in the fourth instar and pupal stages.
The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer” (Fig. 4). The green larva features a dorsal white line down the length of its body, has a dark brown head capsule, and will grow to 9 mm 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” (2018; accessible in either English-enhanced or French-enhanced versions).