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Showing posts with label Alfalfa. Show all posts
Showing posts with label Alfalfa. Show all posts
Monday, 13 July 2020
Insect Pest of the Week and the Entomologists that Study Them (July 13): Alfalfa Pests / Feature entomologist: Tyler Wist
Last week, the Prairie Pest Monitoring Network moved over to our NEW WEBSITE! Click here to read our big news! Same great information and a new format with larger storage capacity. Find the Insect of the Week Feature for Week 12 (Jul 13) over at our new home!
And remember to re-subscribe to the NEW Website to continue to receive all PPMN Updates in your Inbox!
Visit the INSECT OF THE WEEK and WEEKLY UPDATES webpages!
And remember to re-subscribe to the NEW Website to continue to receive all PPMN Updates in your Inbox!
Visit the INSECT OF THE WEEK and WEEKLY UPDATES webpages!
Friday, 19 June 2020
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.
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.
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.
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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 14, 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 14, 2020.
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| 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.
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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).
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.
Friday, 12 June 2020
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.
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.
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).
Thursday, 4 June 2020
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.
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.
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.
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| Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Winnipeg MB. Values are based on model simulations (April 1-May 31, 2020). |
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| 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).
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| Figure 3. Predicted development of populations of alfalfa weevil (Hypera postica) across
the Canadian prairies as of May 31, 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).
Monday, 1 June 2020
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.
Thursday, 28 May 2020
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).
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).
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.
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).
Friday, 22 May 2020
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.
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).
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.
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.
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| Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Saskatoon SK. Values are based on model simulations (April 1-May 18, 2020). |
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| Figure 2. Predicted development of populations of alfalfa weevil (Hypera postica) across
the Canadian prairies as of May 18, 2020.
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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).
Friday, 15 May 2020
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).
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.
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| Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Saskatoon SK. Values are based on model simulations (April 1-May 11, 2020). |
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| 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.
Friday, 8 May 2020
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).
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).
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).
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| Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Lethbridge AB. Values are based on model simulations (April 1-May 4, 2020). |
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| 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).
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.
Thursday, 20 June 2019
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.
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 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.
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| Figure 1. Predicted average instar stage of alfalfa weevil (Hypera postica) populations across
the Canadian prairies as of June 17, 2019.
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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.
Friday, 14 June 2019
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).
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.
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).
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| 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.
Friday, 7 June 2019
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).
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.
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.
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.
Monday, 3 June 2019
Insect of the Week (June 3, 2019) - Doppelgangers: Pea leaf weevil and other Sitona species
The case of the innocuous versus the evil
twin: When making pest management decisions, be sure that the suspect is a actually a pest. This can be
challenge since insects often mimic each other or look
very similar. An insect that looks, moves and acts like a pest may in fact be a
look-alike or doppelganger.
Doppelgangers may be related (e.g. same genus) or may not be related, as in the case monarch butterflies (Danaus plexippus) and viceroys (Limenitis achrippus). In some cases, doppelgangers are relatively harmless. In others, the doppelganger is a pest too yet behaviour, lifecycle and hosts may be different.
Correctly identifying a pest enables selection of the most accurate scouting or monitoring protocol. Identification and monitoring enables the application of economic thresholds. It also enables a producer to select and apply the most effective control option(s) including method and timing of application. For the rest of the growing season, the Insect of the Week will feature insect crop pests and their doppelgangers.
The case of the pea weevil and other Sitona species doppelgangers
Weevils of the genus Sitona are broad-nosed weevils that are pests of various legume crops, including field pea, faba bean, alfalfa and sweet clover. Sitona larvae attack the roots of the host plant and usually consume the root nodules and the enclosed symbiotic bacteria that fix nitrogen. Adult Sitona weevils consume plant leaves resulting in ‘U’-shaped feeding notches. Sitona species known to occur in Canada include:
• Sitona lineatus – pea leaf weevil (Fig. 1), has two primary hosts: field pea and faba bean.
• Sitona cylindricollis – clover root weevil or sweet clover weevil (Fig. 4).
• Sitona hispidulus – clover root curculio* (Fig. 3), a clover pest.
• Sitona lineellus – alfalfa curculio (Fig. 5), eats alfalfa, vetch and field pea.
• Sitona obsoletus (=S. flavescens = S. lepidus) – clover root curculio*, a clover pest (Fig. 6).
* Note that common names can be used to describe more than one species and can be confusing.
Doppelgangers may be related (e.g. same genus) or may not be related, as in the case monarch butterflies (Danaus plexippus) and viceroys (Limenitis achrippus). In some cases, doppelgangers are relatively harmless. In others, the doppelganger is a pest too yet behaviour, lifecycle and hosts may be different.
Correctly identifying a pest enables selection of the most accurate scouting or monitoring protocol. Identification and monitoring enables the application of economic thresholds. It also enables a producer to select and apply the most effective control option(s) including method and timing of application. For the rest of the growing season, the Insect of the Week will feature insect crop pests and their doppelgangers.
The case of the pea weevil and other Sitona species doppelgangers
Weevils of the genus Sitona are broad-nosed weevils that are pests of various legume crops, including field pea, faba bean, alfalfa and sweet clover. Sitona larvae attack the roots of the host plant and usually consume the root nodules and the enclosed symbiotic bacteria that fix nitrogen. Adult Sitona weevils consume plant leaves resulting in ‘U’-shaped feeding notches. Sitona species known to occur in Canada include:
• Sitona lineatus – pea leaf weevil (Fig. 1), has two primary hosts: field pea and faba bean.
• Sitona cylindricollis – clover root weevil or sweet clover weevil (Fig. 4).
• Sitona hispidulus – clover root curculio* (Fig. 3), a clover pest.
• Sitona lineellus – alfalfa curculio (Fig. 5), eats alfalfa, vetch and field pea.
• Sitona obsoletus (=S. flavescens = S. lepidus) – clover root curculio*, a clover pest (Fig. 6).
* Note that common names can be used to describe more than one species and can be confusing.
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| Figure 1. Pea leaf weevil (Sitona lineatus L.). Photo: AAFC-Sasktoon-Williams. |
The above five Sitona species found in Canada are doppelgangers of each other for several reasons:
1. Similar in size and appearance - Require a taxonomic key and microscope to accurately identify to species. Notable difference is Sitona hispidulus which has hairy elytra compared to the other four species which lack hair on their elytra (Fig. 2).
2. Sitona weevils share primary and secondary hosts - Pea leaf weevils must feed on primary hosts (i.e., field pea and faba bean) to attain sexual maturation AND the larvae must feed on primary hosts to successfully develop. However, early in the spring and again in the fall, pea leaf weevils feed on virtually any species of legume, including the primary host plants of the other four Sitona species.
3. Foliar feeding damage is similar - According to Weich and Clements (1992), “careful scrutiny” is required to differentiate the feeding damage caused by different Sitona species feeding on the same host plant. Therefore, it is important to collect adult weevils for identification to confirm which species is responsible for foliar damage.
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| Figure 2. Characteristics of four of the five Sitona species found in Canada, useful when scouting for pea leaf weevils. See also the pea leaf weevil monitoring protocol. Images © AAFC-Beaverlodge |
Species pages for all five species
available by searching the species names in the E.H. Strickland Entomology
Museum: http://www.entomology.museums.ualberta.ca/searching.php
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| Figure 3. Clover root curculio (Sitona hispicula Fabricious). Photo: © Donald Hobern |
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| Figure 4. Sweet clover weevil (Sitona cylindricollis Fahreaus). Photo: © Janet Graham. |
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| Figure 5. Alfalfa curculio (Sitona lineellus Bonsdorff). Photo: © by nc Chris Moody. |
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| Figure 6. Clover root curculio (Sitona obsoletus). Photo: by K. Walker |
More information about pea leaf weevil (Sitona lineatus), and sweetclover weevil (Sitona cylindricollis) can be accessed on the Insect of
the Week page. Information
related to crop pests and their natural enemies can be found in the newly
updated Field Guide and Cutworm
Guide. Both are available for free download on
our Insect
Field Guide and Cutworm
Field Guide pages.
Friday, 31 May 2019
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.
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.
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.
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| Figure 1. Projected predicted status of alfalfa weevil populations near Brooks AB to June 15, 2019,using long term average temperatures. |
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| 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.
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