Tag: Hypera postica

Alfalfa weevil

The alfalfa weevil, Hypera postica, overwinters as an adult that typically flies to alfalfa fields in April and May. Adult females start to lay eggs in May. Adults consume alfalfa foliage, but typically do not cause economic levels of damage. However, larval feeding peaks in June and, if high densities are present, can cause yield losses. Thus, field scouting to assess larval stages and densities should begin in May through to June. Review the alfalfa weevil life cycle and the damage it causes.

Reminder – The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer” (Fig. 1). 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. Alfalfa growers are encouraged to check the Alfalfa Weevil Monitoring Protocol prepared by Dr. Julie Soroka (AAFC-Saskatoon).

**Figure 1.** Alfalfa weevil injury to alfalfa; (a, b) leaf notching and skeletonizing and (c) injury to stem tips. Photos: AAFC-Soroka.

Economic Thresholds and Control:
Economic thresholds for alfalfa weevil vary with the alfalfa crop type (whether hay or seed) the advising body, and the measurable unit. In hay fields, forage losses can be economic if one or more of the following symptoms are noted:
• if 25-50 % of the leaves on the upper one-third of the stem show damage, or
• if 50-70% of the terminals are injured, or
• if 1 to 3 third or fourth instar larvae occur per stem (with shorter stems having lower economic thresholds and 3 or more larvae requiring treatment no matter what the alfalfa height), or
• 20-30 larvae per sweep occur when 12 % leaf loss is acceptable.
Early cutting of the first growth of alfalfa or insecticide treatment will reduce alfalfa weevil populations. If the hay crop value is high and weevil injury is seen or 2 or more larvae per stem reappear in regrowth after cutting, insecticide may be necessary if a second cut is anticipated. In alfalfa seed fields, economic thresholds are 20-25 third to fourth instar larvae per sweep or 35-50 % of the foliage tips showing damage. Thresholds increase with the height of the alfalfa, and decrease in drought conditions. Several small wasps parasitize alfalfa weevil larvae and adults, and in the past these natural control agents kept the weevil in check in most years. One of these wasps, Bathyplectes curculionis (Thomson), (Fig. 3a-c), parasitizes alfalfa weevil in Alberta and Saskatchewan, and is now found in Manitoba.

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 as a free downloadable PDF in either English or French on our new Field Guides page.

Alfalfa weevil

Predicted alfalfa weevil development

The alfalfa weevil (AAW) (Curculionidae: Hypera postica) model predicts development using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Review lifecycle and damage information for this pest.

Model simulations for alfalfa weevil (AAW) indicate third instar larvae should now be appearing across the prairies. Development is similar to long-term average values. AAW development in central Saskatchewan (Fig. 1) is slower than AAW development in southern Alberta (Fig. 2).

Figure 1. Predicted status of alfalfa weevil (*Hypera postica*) populations near Saskatoon SK as of June 12, 2022.

Figure 2. Predicted status of alfalfa weevil (*Hypera postica*) populations near Medicine Hat AB as of June 12, **2022**.

Predicted alfalfa weevil development

Model simulations for alfalfa weevil (AAW) indicate the appearance of first and second instar larvae should be occurring across the prairies. Development in southern Manitoba (Fig. 1) is slower than development in southern Alberta (Fig. 2). Development is similar to long-term average values.

Figure 1. Predicted status of alfalfa weevil (*Hypera postica*) populations near Winnipeg MB as of June 5, 2022.

Figure 2. Predicted status of alfalfa weevil (*Hypera postica*) populations near Medicine Hat AB as of June 5, **2022**.

Predicted alfalfa weevil development

Model simulations for alfalfa weevil (AAW) indicate initial hatch should be occurring across southern and central regions of Alberta and Saskatchewan. First and second instar larvae are predicted to appear in alfalfa fields near Medicine Hat.

The following graphs indicate, based on potential number of eggs, that development is marginally faster near Vauxhall, Alberta (Fig. 1), compared to Saskatoon, Saskatchewan (Fig. 2). Development is similar to long-term average values. The model predicts that first and second instar larval populations may peak over the next 10 days near these two locations.

Figure 1. Predicted status of alfalfa weevil (*Hypera postica*) populations near Vauxhall AB as of May 29, 2022.

Figure 2. Predicted status of alfalfa weevil (*Hypera postica*) populations near Saskatoon SK as of **May 29, 2022**.

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 as a free downloadable PDF in either English or French on our new Field Guides page.

Predicted alfalfa weevil development

Model simulations for alfalfa weevil (AAW) indicate that oviposition should be well underway across the prairies. The following graphs indicate, based on potential number of eggs, that development is marginally slower near Lethbridge, Alberta (Fig. 1) than Saskatoon, Saskatchewan (Fig. 2). The model predicts that hatch should begin next week.

Figure 1. Predicted status of alfalfa weevil (*Hypera postica*) populations near Lethbridge AB as of May 22, 2022.

Figure 2. Predicted status of alfalfa weevil (*Hypera postica*) populations near Saskatoon SK as of **May 22, 2022**.

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 as a free downloadable PDF in either English or French on our new Field Guides page.

Predicted alfalfa weevil development

Model simulations for alfalfa weevil (AAW) indicate that oviposition should be well underway across the prairies as of May 15, 2022. The following graphs indicate, based on potential number of eggs, that development is slower near Lethbridge (Fig. 1) than Saskatoon (Fig. 2).

Development for both locations is ahead of average. The model predicts that eggs may begin hatching next week.

Figure 1. Predicted status of alfalfa weevil (*Hypera postica*) populations near Lethbridge AB as of May 15, 2022.

Figure 2. Predicted status of alfalfa weevil (*Hypera postica*) populations near Saskatoon SK as of **May 15, 2022**.

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 as a free downloadable PDF in either English or French on our new Field Guides page.

Predicted alfalfa weevil development

As of May 8, model simulations for alfalfa weevil (AAW) predict that oviposition is well underway across the prairies. The following graphs indicate, based on the potential number of eggs, that development is slower near Lethbridge (Fig. 1) than Saskatoon (Fig. 2). Development for both locations is ahead of that expected based on long-term averages. The model predicts that hatch may occur during the last week of May.

Figure 1. Predicted status of alfalfa weevil (*Hypera postica*) populations near Lethbridge AB as of May 8, 2022.

Figure 2. Predicted status of alfalfa weevil (*Hypera postica*) populations near Saskatoon SK as of **May 8, 2022.**

Predicted alfalfa weevil development

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.

Figure 1. Predicted percent of *Hypera postica* (alfalfa weevil) population in the third instar stage **as of June 13, 2021**.

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.

Figure 2. Predicted status of alfalfa weevil (*Hypera postica*) development for populations near Brandon, Manitoba as of June 13, 2021 (projected to June 29, 2021).

Figure 3. Predicted status of alfalfa weevil (*Hypera postica*) development for populations **near Swift Current, Saskatchewan as of June 13, 2021 (projected to June 29, 2021)**.

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).

Predicted alfalfa weevil development

Model simulations for alfalfa weevil (AAW) (Hypera postica) predict, as of June 6, that alfalfa weevil populations should be primarily in the second larval instar (Fig. 1). The following graph indicates the predicted development near Brandon (Fig. 2). This week, larval populations in southern Manitoba should be primarily in the second instar. Simulation runs indicate that by June 22, southern Manitoba populations will be in the fourth instar with initial appearance of pupae.

Figure 1. Predicted development of *Hypera postica* (alfalfa weevil) populations across the prairies as of June 6, 2021.

Figure 2. Predicted status of alfalfa weevil *(Hypera postica*) development for populations near Brandon, Manitoba **as of June 6, 2021 (projected to June 22, 2021).**

The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer” (Fig. 3). 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).

Predicted alfalfa weevil development

Model simulations for alfalfa weevil (AAW) predict, as of May 30, that egg hatch should be nearly complete across Manitoba and Saskatchewan. First instar larvae should be appearing across most of Manitoba (Fig. 1). The following graphs indicate that development is more advanced near Winnipeg (Fig. 2) than near Lethbridge (Fig. 3). This week, larval populations in southern Manitoba should be primarily in the second instar while populations in southern Alberta may consist of first instar larvae. Results suggest that by June 15, populations will be in the second and third larval instars across southern Alberta and that Manitoba populations will be in third and fourth instar stages.

Figure 1. Predicted development of Hypera postica (alfalfa weevil) populations across the prairies as of May 30, 2021.

Figure 2. Predicted status of alfalfa weevil (Hypera postica) development for populations near Winnipeg, Manitoba as of May 30, 2021 (projected to June 15, 2021).

Figure 3. Predicted status of alfalfa weevil (Hypera postica) development for populations near Lethbridge, Alberta as of May 30, 2021 (projected to June 15, 2021).

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).

Alfalfa weevil predicted development

Model simulations for alfalfa weevil (AAW) predict that oviposition should be well underway across the prairies. The following graphs indicate that development is similar near Swift Current SK (Fig. 1) and Brandon MB (Fig. 2). The model predicts that that hatch may occur during the last week of May and that second instar larvae could be present during the first week of June.

Figure 1. Projected predicted status of alfalfa weevil (Hypera postica) populations near
Swift Current SK as of May 23, 2021 (projected to June 7, 2021).

Figure 2. Projected predicted status of alfalfa weevil (*Hypera postica*) populations near
Brandon MB **as of May 23, 2021 (projected to June 7, 2021).**

The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer” (Fig. 3). 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.

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).

Alfalfa weevil predicted development

Model simulations for alfalfa weevil (AAW) predict that oviposition should be well underway across the prairies. The following graphs indicate that development is similar near Swift Current (Fig. 1) and Brandon (Fig. 2). The model predicts that that hatch may occur during the last week of May.

Figure 1. Projected predicted status of alfalfa weevil populations near Swift Current SK as of May 16, 2021 (projected to May 31, 2021).

Figure 2. Projected predicted status of alfalfa weevil populations near Brandon MB as of May 16, 2021 (projected to May 31, 2021).

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).

Alfalfa weevil predicted development

Model simulations for alfalfa weevil (AAW) indicate that oviposition should be well underway across 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). The model predicts that hatch may occur during the last week of May.

**Figure 1**. Projected predicted status of alfalfa weevil populations near Lethbridge AB as of May 9, 2021.

**Figure 2**. Projected predicted status of alfalfa weevil populations near Brandon MB as of May 9, 2021.

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).

Alfalfa weevil predicted development

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 simulations for alfalfa weevil (AAW) 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 Regina SK (Fig. 1) than Winnipeg MB (Fig. 2).

Figure 1. Projected predicted status of alfalfa weevil populations near Regina SK as of May 2, 2021.

Figure 2. Projected predicted status of alfalfa weevil populations near Winnipeg MB as of May 2, 2021.

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 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).