As of June 7, 2020, model output indicates that hatch of alfalfa weevil eggs is almost complete, as only 20% of the population is expected to currently be in the egg stage (prairie average). Prairie populations are predominantly in the first (29%) or second (36%) instar larval stages (Fig. 1) and approximately 15% are predicted to be third instar larvae (Table 1; Fig. 2). Developmental rates should be greatest across southern Manitoba and southeastern Saskatchewan.
Table 1. Predictive model output estimates for Hypera postica development (% of total population for each location) at selected sites across the Canadian prairie as of June 7, 2020.
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| Figure 1. Predicted percent of populations of alfalfa weevil (Hypera postica) in the second instar stage across
the Canadian prairies as of June 7, 2020.
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| Figure 2 Predicted percent of populations of alfalfa weevil (Hypera postica) in the third instar stage across
the Canadian prairies as of June 7, 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).
