Alfalfa weevil

Alfalfa Weevil (Hypera postica) – Model output indicates that hatch is almost complete with less than 5% of the population predicted to still be in the egg stage (prairie average; Table 1). Across the prairies, populations are predicted to be 12, 45, 29 and 10% in first, second, third and fourth instars, respectively.  

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 14, 2020.

Larval populations in the Peace River region are expected to be mostly in the second instar (Fig. 1).  Last week, the presence of third instar larvae was limited to areas southeast of Saskatchewan and extended into Manitoba (Fig. 2).  This week third instar larvae should be occurring across southern and central regions of the prairies (Fig. 3).  Fourth instar larvae should be abundant across southern Manitoba and southeastern Saskatchewan.

Figure 1. Predicted percent of populations of alfalfa weevil (Hypera postica) in the second instar stage across

the Canadian prairies as of June 14, 2020. 

Figure 2. Predicted percent of populations of alfalfa weevil (Hypera postica) in the third instar stage across

the Canadian prairies as of June 14, 2020. 

Figure 3. Predicted percent of populations of alfalfa weevil (Hypera postica) in the fourth instar stage across

the Canadian prairies as of June 14, 2020. 

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).  

Figure 3.  Developmental stages of the alfalfa weevil (Hypera postica); overwintered adult (upper row L-R), eggs, larvae, larva feeding or "skeletonizing" alfalfa leaf (lower row L-R), pupa within lacey cocoon, pupa, and newly emerged adult.

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. 2018). The guide is available as an English-enhanced or French-enhanced version.

Alfalfa weevil

Alfalfa Weevil (Hypera postica) – Degree-day maps of base 9 °C are produced to predict the development of Alfalfa weevil (AAW) across the prairies.  The model is updated weekly to help growers time their in-field scouting for second-instar larvae. 

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.

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. 

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. 

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).  

Figure 3.  Developmental stages of the alfalfa weevil (Hypera postica); overwintered adult (upper row L-R), eggs, larvae, larva feeding or "skeletonizing" alfalfa leaf (lower row L-R), pupa within lacey cocoon, pupa, and newly emerged adult.

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. 2018). The guide is available as an English-enhanced or French-enhanced version.

Alfalfa weevil

Alfalfa Weevil (Hypera postica) – Degree-day maps of base 9 °C are produced to predict the development of Alfalfa weevil (AAW) across the prairies.  The model is updated weekly to help growers time their in-field scouting for second-instar larvae. 

As of May 31, 2020, model output indicates that hatch is well underway and both first and second instar larvae may be occurring in alfalfa fields across southern Manitoba and Saskatchewan (Table 1). The following graphs compare development for Winnipeg (Fig. 1) and Swift Current (Fig. 2). At Winnipeg (Fig. 1), AAW populations are predicted to be primarily in the second instar. Weevil populations near Swift Current (Fig. 2) are expected to consist mostly of first instar larvae. If present, the model predicts that populations in the southern Peace River region would primarily still be in the egg stage (Table 1).  

Table 1.  Predictive model output estimates for Hypera postica populations at selected sites across the Canadian prairie as of May 31, 2020.

Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Winnipeg MB.
Values are based on model simulations (April 1-May 31, 2020).

Figure 2. Predicted alfalfa weevil (Hypera postica) phenology at Swift Current SK.
Values are based on model simulations (April 1-May 31, 2020).

The map below (Fig. 3) indicates areas where populations should have second instar larvae (% of total population).

Figure 3. Predicted development of populations of alfalfa weevil (Hypera postica) across

the Canadian prairies as of May 31, 2020. 

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).  

Figure 3.  Developmental stages of the alfalfa weevil (Hypera postica); overwintered adult (upper row L-R), eggs, larvae, larva feeding or "skeletonizing" alfalfa leaf (lower row L-R), pupa within lacey cocoon, pupa, and newly emerged adult.

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. 2018). The guide is available as an English-enhanced or French-enhanced version.

Pest Alert

Important for scouting this week - Click to access two updates related to in-field scouting released June 2!

• The predicted emergence of the first Bertha armyworm of 2020 across the Canadian prairies  (which helps time the deployment of pheromone traps).
• Predicted development of alfalfa weevil to help time in-field scouting for damaging larval stages of Alfalfa weevil.

Alfalfa weevil

Alfalfa Weevil (Hypera postica) – Degree-day maps of base 9 °C are produced to predict the development of Alfalfa weevil (AAW) across the prairies.  The model is updated weekly to help growers time their in-field scouting for second-instar larvae. 

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). 

Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Winnipeg MB.
Values are based on model simulations (April 1-May 25, 2020).

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). 

Figure 3. Predicted development of populations of alfalfa weevil (Hypera postica) across

the Canadian prairies as of May 25, 2020. 

Figure 4. Predicted percent of alfalfa weevil (Hypera postica) at first instar stage across

the Canadian prairies as of May 25, 2020. 

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).  

Figure 3.  Developmental stages of the alfalfa weevil (Hypera postica); overwintered adult (upper row L-R), eggs, larvae, larva feeding or "skeletonizing" alfalfa leaf (lower row L-R), pupa within lacey cocoon, pupa, and newly emerged adult.

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. 2018). The guide is available as an English-enhanced or French-enhanced version.

Alfalfa weevil

Alfalfa Weevil (Hypera postica) – Degree-day maps of base 9 °C are produced to predict the development of Alfalfa weevil (AAW) across the prairies.  The model is updated weekly to help growers time their in-field scouting for second-instar larvae. 

Model output indicates that oviposition is well underway and initial hatch should occur over the next 7-10 days  (Fig. 1). Compared with long term normal weather data, egg development is 1 – 2 days later than average.  Based on the alfalfa weevil degree day model (Soroka et al. 2020), AAW development is most advanced across southern AB.

Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Saskatoon SK.
Values are based on model simulations (April 1-May 18, 2020).

Figure 2. Predicted development of populations of alfalfa weevil (Hypera postica) across

the Canadian prairies as of May 18, 2020. 

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. 33, upper right).  

Figure 3.  Developmental stages of the alfalfa weevil (Hypera postica); overwintered adult (upper row L-R), eggs, larvae, larva feeding or "skeletonizing" alfalfa leaf (lower row L-R), pupa within lacey cocoon, pupa, and newly emerged adult.

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. 2018). The guide is available as an English-enhanced or French-enhanced version.

Alfalfa weevil

Alfalfa Weevil (Hypera postica) – As a result of warmer temperatures in Saskatchewan (compared to Manitoba), AAW development is predicted to be greater in Saskatchewan.  The following graphs indicate, based on potential number of eggs (red line), that development is more advanced near Saskatoon (Fig. 1) than Brandon (Fig. 2).

Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Saskatoon SK.
Values are based on model simulations (April 1-May 11, 2020).

Figure 2. Predicted alfalfa weevil (Hypera postica) phenology at Brandon MB.
Values are based on model simulations (April 1-May 11, 2020).

 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. 2018). The guide is available as an English-enhanced or French-enhanced version.

Alfalfa weevil

Alfalfa Weevil (Hypera postica) – Degree-day maps of base 9 °C are produced to predict the development of Alfalfa weevil (AAW) across the prairies.  The model is updated weekly to help growers time their in-field scouting for second-instar larvae. 

As of May 4, 2020, AAW model simulations indicate that oviposition should have begun across central and western areas of the prairies.  The following graphs indicate, based on potential number of eggs, that development is more advanced near Lethbridge (Fig. 1) than Brandon (Fig. 2).

Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Lethbridge AB.
Values are based on model simulations (April 1-May 4, 2020).

Figure 2. Predicted alfalfa weevil (Hypera postica) phenology at Brandon MB.
Values are based on model simulations (April 1-May 4, 2020).

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).  

Figure 3.  Developmental stages of the alfalfa weevil (Hypera postica); overwintered adult (upper row L-R), eggs, larvae, larva feeding or "skeletonizing" alfalfa leaf (lower row L-R), pupa within lacey cocoon, pupa, and newly emerged adult.

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. 2018). The guide is available as an English-enhanced or French-enhanced version.

Alfalfa weevil (June 20, 2019; Wk 11)

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. 

Alfalfa weevil larval populations are developing into later instars (Fig. 1). Second instar development is nearing completion and this week there larvae should be in the third instar stage. This week larvae are mostly second (26%, 52% last week) and third instars (52%, 22% last week; Fig. 1). Model output indicates that fourth instar larvae are beginning to occur in southern SK and isolated areas in southern AB and MB.

Figure 1. Predicted average instar stage of alfalfa weevil (Hypera postica)  populations across

the Canadian prairies as of June 17, 2019. 

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.

Alfalfa weevil (June 13, 2019; Wk 10)

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. 

This past week warmer temperatures in southern MB advanced alfalfa weevil development. Weevils are predicted to be primarily in the second (53%) and third instars (22%) across most of southern areas in MB and SK (Fig. 1).

Figure 1. Predicted average instar stage of alfalfa weevil (Hypera postica)  acrossthe Canadian prairies as of June 11, 2019.

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.

Alfalfa weevil (June 6, 2019; Wk 09)

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. 

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). 

Figure 1. Percent of populations of alfalfa weevil (Hypera postica)  in the first instar stage across
the Canadian prairies as of June 3, 2019. 

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.

Figure 3. Predicted status of alfalfa weevil populations near Brooks AB projected to June 21, 2019, using
long term average temperatures.

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.

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.

Alfalfa weevil (May 23, 2019; Wk 07)

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 output indicates that alfalfa weevil hatch has begun and first instar alfalfa weevils should be present across most of AB (Fig. 1). Model runs for Brooks AB (Fig. 2) and Swift Current SK (Fig. 3) were projected to June 15, 2019.  Second instar larvae will begin to occur late next week in fields near Brooks and 3-5 days later in the Swift Current region. 

Figure 1.  Predicted percent of grasshopper (Melanoplus sanguinipes) population at first instar stage across
the Canadian prairies (as of May 21, 2019). 

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

Figure 3.  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.

Alfalfa weevil (May 16, 2019; Wk 06)

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 (Fig. 1) and Swift Current SK (Fig. 2) were projected to June 15, 2019.  Model output indicates that initial hatch should occur late next week in fields near Brooks. Hatch should be 5-7 days later in the Swift Current region. Compared to last year’s runs for Swift Current, development is predicted to be 10 days later than 2018. Compared with long term normal weather data, egg development is 1 – 2 days later than average. 

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.