As of May 25, 2020, the model output indicates that oviposition is well underway and initial hatch has begun in some locations. The following graphs compare development for Winnipeg (Fig. 1) and Lethbridge (Fig. 2). At Winnipeg, first instar larvae are expected to occur already (Fig. 1) while first instar larvae should begin to appear later this week in southern AB (Fig. 2).
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| Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Winnipeg MB. Values are based on model simulations (April 1-May 25, 2020). |
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| Figure 2. Predicted alfalfa weevil (Hypera postica) phenology at Lethbridge AB. Values are based on model simulations (April 1-May 25, 2020). |
Based on the alfalfa weevil degree day model (Soroka et al. 2020), AAW development is most advanced across southern SK (Fig. 3). The second map (Fig. 4) presents occurrence of first instar larvae (% of total population).
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| Figure 3. Predicted development of populations of alfalfa weevil (Hypera postica) across
the Canadian prairies as of May 25, 2020.
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| Figure 4. Predicted percent of alfalfa weevil (Hypera postica) at first instar stage across
the Canadian prairies as of May 25, 2020.
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Monitoring
The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer” (Fig. 3, lower left). The green larva featuring a dorsal, white line down the length of its body has a dark brown head capsule and will grow to 9 mm long (Fig. 3, upper right).
