Weather conditions continue to be favourable for development of alfalfa weevil, if alfalfa weevil are present in your area. First instar development is nearing completion (Fig. 1) and the more individuals in the population should be in the second instar stage (Fig. 2).
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| Figure 1. Percent of populations of alfalfa weevil (Hypera postica) in the first instar stage across the Canadian prairies as of June 3, 2019. |
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| Figure 2. Percent of populations of alfalfa weevil (Hypera postica) in the second instar stage across the Canadian prairies as of June 3, 2019. |
Model runs for Brooks AB (Fig. 3) and Swift Current SK (Fig. 4) were projected to June 21, 2019. In alfalfa fields near Brooks AB larvae should start to reach the third instar stage late this week. At Swift Current SK third instar larvae will begin to appear approximately 5-7 days later.
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| Figure 3. Predicted status of alfalfa weevil populations near Brooks AB projected to June 21, 2019, using long term average temperatures. |
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| Figure 4. Predicted status of alfalfa weevil populations near Swift Current SK projected to June 21, 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.