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 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.
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.
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.
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.
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.
Figure 3. Developmental stages of the alfalfa weevil (Hypera postica). Composite image: J. Soroka (AAFC-Saskatoon).
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).
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).
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.
Figure 4. Developmental stages of the alfalfa weevil (Hypera postica). Composite image: J. Soroka (AAFC-Saskatoon).
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).
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.
Figure 3. Developmental stages of the alfalfa weevil (Hypera postica). Composite image: J. Soroka (AAFC-Saskatoon).
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).
The pea leaf weevil is a slender greyish-brown insect measuring approximately 5 mm in length (Fig. 1, Left image). Pea leaf weevil resembles the sweet clover weevil (Sitona cylindricollis) but the former is distinguished by three light-coloured stripes extending length-wise down thorax and sometimes the abdomen. All species of Sitona, including the pea leaf weevil, have a short snout.
Figure 1. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (AAFC-Otani).
Adults will feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas) and produce a characteristic, scalloped (notched) edge (Fig. 2). Females lay their eggs in the soil either near or on developing pea or faba bean plants from May to June.
Figure 2. Examples of adult pea leaf weevil damage on field pea seedlings, (A) seedling with notches on all nodes, (B) stereotypical crescent shaped notches on the leaf margin, (C) clam or terminal leaf of the pea seedling with arrows indicating the feeding notches. All photos courtesy of Dr. L. Dosdall.
Larvae develop under the soil and are “C” shaped and milky-white with a dark-brown head capsule ranging in length from 3.5-5.5 mm (Figure 3). Larvae develop through five instar stages. After hatching, larvae seek and enter the roots of a pea plant. Larvae will enter and consume the contents of the nodules of the legume host plant. It is the nodules that are responsible for nitrogen-fixation which affect yield plus the plant’s ability to input nitrogen into the soil. Consumption of or damage to the nodules (Figure 4) results in partial or complete inhibition of nitrogen fixation by the plant and results in poor plant growth and low seed yields.
Figure 3. Larva of pea leaf weevil in soil (Photo: L. Dosdall).Figure 4. Damaged pea nodules (Photo: L. Dosdall).
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).
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).
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.
Figure 3. Developmental stages of the alfalfa weevil (Hypera postica). Composite image: J. Soroka (AAFC-Saskatoon).
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 (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-enhancedor French-enhanced version.
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-enhancedor French-enhanced version.
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-enhancedor French-enhanced version.
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.
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.
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.
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-enhancedor French-enhanced version.
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 alfalfa weevil (Hypera postica) populations 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-enhancedor French-enhanced version.
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-enhancedor French-enhanced version.
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.
AAW model runs indicate that oviposition should have begun in the Brooks (Rosemary) AB (Fig. 1) and Regina SK regions (Fig. 2). Note that this week’s cool temperatures have reduced oviposition rates (based on model predictions).
Figure 1. Predicted status of alfalfa weevil populations near Swift Current SK as of May 7, 2019.
Figure 2. Predicted status of alfalfa weevil populations near Swift Current SK as of May 7, 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-enhancedor French-enhanced version.
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 (Hypera postica) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae.
The AAW model runs indicate that oviposition has begun in fields near Swift Current SK (Fig. 1). Compared to last week, oviposition rates are predicted to have increased.
Figure 1. Predicted AAW adults near Swift Current SK as of April 30, 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-enhancedor French-enhanced version.
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 (Hypera postica) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. Compare the following predicted development stages and degree-day values from Soroka (2015) to the map below (Fig. 1).
Alfalfa weevil (AAW) model runs indicate that oviposition may have begun in fields near Swift Current SK.
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-enhancedor French-enhanced version.
This week’s Insect of the Week is the twospotted spider mite. This tiny mite is 0.5 mm long and has eight legs. It has a greenish, yellowish to orange oval body with two dark spots on its abdomen. To the unaided eye, it looks like a small speck. they feed on corn, soybean, dry beans, alfalfa, vegetables and fruit.
These mites overwinter in protected sites as eggs, immatures or adults depending on food hosts and habitat. Immatures and adults move to emerging plant hosts in the spring. They create webbing on the underside of leaves where they puncture cells to feed on cell contents. This feeding causes stippling, yellowing or browning of the leaves. Leaves may dry and drop which can further reduce crop yields.
Infestations start at the field edge and move inwards. Extended hot, dry conditions favour rapid population build up and exacerbate feeding injury.
For more information on the twospotted spider mite, check out our Insect of the Week page!
Twospotted spider mite – adult closeup David Cappaert, Michigan State University, Bugwood.orgTwospotted spider mite – stippling damage on bean Whitney Cranshaw, Colorado State University, Bugwood.org
This week’s insect of the week is the pea aphid (Acyrthosiphon pisum). This long-legged, pear-shaped aphid is 3-4 mm long, light to dark green and each antennal segment is tipped by a black band. It feeds on field peas, alfalfa, broad beans, chickpeas, clover and lentils. Feeding damage can reduce yields due to lower seed formation and seed size. Leaves may turn yellow and overall plant growth can be delayed.
Pea aphids overwinter as eggs on the leaves and stems of perennial legumes (eg. clover or alfalfa crowns). They produce 2-3 generations asexually before winged females migrate to summer host crops where several more generations are produced. Winged sexual forms develop in late summer that mate and females return to winter host crops to lay eggs.
Alfalfa Weevil (Hypera postica) – Approximately 70% of the population should be in the third or fourth instar stages and pupae may be occurring as well. AAW populations near Winnipeg, Brandon, Regina, Saskatoon and regions in southern Alberta are predicted to be primarily in the fourth instar (Fig. 1).
Figure 1. Average predicted development stages of alfalfa weevil. Values are based on model simulations (April 1-June 11, 2018).
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-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – The AAW model runs for Swift Current SK indicate that oviposition is well underway in southern Saskatchewan (Fig. 1). Larvae should be primarily second and third instars. Fourth instar larvae may be occurring as well.
Figure 1. Average developmental alfalfa weevil stage. Values are based on model simulations, for April 1-June 4, 2018.
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.
Use the photo below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape of the abdomen and the dark head capsule.
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-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – The AAW model runs for Swift Current SK indicate that oviposition is well underway in southern Saskatchewan (Fig. 1). Larvae should be primarily second and third instars. Fourth instar larvae may be occurring as well.
Figure 1. Predicted alfalfa weevil phenology at Swift Current SK.
Values are based on model simulations (April 1-May 28, 2018 and projected to June 21, 2018).
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 (Hypera postica) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. Compare the following predicted development stages and degree-day values from Soroka (2015) to the map below (Fig. 2).
Figure 2. Predicted development of alfalfa weevil as of May 30, 2018.
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.
Use the photo below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape of the abdomen and the dark head capsule.
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-enhancedor French-enhanced version.
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 (Hypera postica) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. Compare the following predicted development stages and degree-day values from Soroka (2015) to the map below (Fig. 1).
The AAW model runs suggest thatoviposition should be well underway in southern Saskatchewan. Larvae should be in the first and second instars.
Figure 1. Predicted development of alfalfa weevil as of May 21, 2018.
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.
Use the photo below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape of the abdomen and the dark head capsule.
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-enhancedor French-enhanced version.
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 (Hypera postica) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. Compare the following predicted development stages and degree-day values from Soroka (2015) to the map below.
The alfalfa weevil model predicts that oviposition is well underway in southern Saskatchewan. Figure 1 shows model output for Swift Current where first instar larvae should appear early next week.
Figure 1. Predicted alfalfa weevil (Hypera postica) phenology at Swift Current SK.
Values are based on model simulations for April 1-May 6, 2018.
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.
Use the photo below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape of the abdomen and the dark head capsule.
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-enhancedor French-enhanced version.
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 (Hypera postica) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. Compare the following predicted development stages and degree-day values from Soroka (2015) to the map below.
The AAW model predicts that oviposition may have begun in southern areas of the prairies. Current oviposition rates are predicted to be higher than oviposition rates based on LTN climate data (Fig. 1).
Figure 1. Predicted AAW oviposition at four prairie locations. Values are based on
model simulations, for April 1 – May 6, 2018.
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.
Use the photo below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape of the abdomen and the dark head capsule.
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-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – Across the prairies, the model indicates that 95% of the population should be in the pupal stage. This week adults should be appearing at most locations. Output indicates that adult emergence is well underway at many southern locations (Brooks, Estevan) , while adult emergence at many central locations (Saskatoon) has begun over the last five days.
In terms of degree-day heat units, the map below reflects the predicted development of alfalfa weevil across the Canadian prairies.
Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon) and 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). That guide is available in both a free English-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – Across the prairies, the model indicates that 80% of the population should be in the pupal stage. Adults should be appearing near Saskatoon this week.
In terms of degree-day heat units, the map below reflects the predicted development of alfalfa weevil across the Canadian prairies.
Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon) and 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). That guide is available in both a free English-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – The model output for alfalfa weevil is not signficantly different that that posted last week for June 22nd (Week 7).
Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon) and 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). That guide is available in both a free English-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – Recent warm weather has resulted in rapid alfalfa weevil development. Model output indicates that 98% of the hatch is complete (less than 80% last week). Larval populations should be predominantly in the second (35%) and third (46%) instars.
Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon) and 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). That guide is available in both a free English-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – Reminder – Biological information and photos of all life stages of this insect can reviewed on the Week 4 post. The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer”. Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. Models predicting the development of Alfalfa weevil across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. Compare the following predicted development stages and degree-day values from Soroka (2015) to the map below.
As of June 4, 2017, the recent warm weather has resulted in rapid development, indicating that 80% of the hatch is probably complete (less than 20% last week). Larval populations should be predominantly in the first and second instars (less than 10% are predicted to be third instars).
Figure 1. Heat units accumulated necessary for the development of Alfalfa weevil (Hypera postica) across the Canadian prairies (April 1-June 4, 2017).
Remember – Use the photo below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape of the abdomen and the dark head capsule.
Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon) and 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). That guide is available in both a free English-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – Reminder – Biological information and photos of all life stages of this insect can reviewed on the Week 4 post. The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer”.
Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. Models predicting the development of Alfalfa weevil across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. Compare the following predicted development stages and degree-day values from Soroka (2015) to the map below.
As of May 29, 2017, embryological development (hatch) is predicted to be greatest across south and central regions of the prairies (Fig. 2).
Figure 1. Heat units accumulated necessary for the development of Alfalfa weevil (Hypera postica)
across the Canadian prairies (April 1-May 29, 2017).
The map below reflects the predicted stage of development of alfalfa weevil (as of May 29th) and suggests the percent of the population at first instar stage across the Canadian prairies (as of May 29th).
Figure 2. Predicted percent of H. postica population at first instar stage
across the Canadian prairies (as of May 29, 2017).
Use the photo below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape of the abdomen and the dark head capsule.
Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon) and 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). That guide is available in both a free English-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – 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).
Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. Models predicting the development of Alfalfa weevil (Hypera postica) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. Compare the following predicted development stages and degree-day values from Soroka (2015) to the map below.
This week, embryological development is greatest across south and central regions of Alberta and Saskatchewan and across southern Manitoba. Early hatch is predicted to occur in a region near Brooks AB and Regina SK and south to the USA border.
Use the figure below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape of the abdomen and the dark head capsule.
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-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – 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).
Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. Models predicting the development of Alfalfa weevil (Hypera postica) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae. Compare the following predicted development stages and degree-day values from Soroka (2015) to the map below.
This week, the predictive model output for Brooks AB suggests that oviposition is well underway (i.e., in areas of the map below highlighted chocolate-brown). The initial first instar larvae may occur by next week.
Use the figure below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape of the abdomen and the dark head capsule.
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-enhancedor French-enhanced version.
Alfalfa Weevil (Hypera postica) – 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). Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur. Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.
This week, alfalfa growers in southern Alberta and southern Saskatchewan (areas of the map highlighted tan) are on the verge of predicted egg hatch of the alfalfa weevil.
Use the figure below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape and the dark head capsule.
Alfalfa Weevil (Hypera postica) – Descriptions related to the biology, monitoring and management of this insect can be reviewed on Week 12’s Post.
For the week of July 27, 2016, the following map predicts that sufficient heat units have accumulated across the prairies for alfalfa weevils to be present.
Economic thresholds for Alfalfa weevil (adapted from Soroka 2015) vary by crop type (hay or seed), area fed upon and larval densities.
Reminder – 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. ● Also know that 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), parasitizes alfalfa weevil in Alberta and Saskatchewan, and is now found in Manitoba.
Alfalfa Weevil (Hypera postica) – Reminder – 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).
Updated – Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur. Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.
For the week of July 17, 2016, the following map predicts the developmental stages for alfalfa weevil and corresponding degree-days. Areas highlighted orange are predicted to find fourth instar larvae so scout for major leaf feeding then compare larval densities to the action threshold for alfalfa weevil!
Economic thresholds for Alfalfa weevil (adapted from Soroka 2015) vary by crop type (hay or seed), area fed upon and larval densities. 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. ● Also consider these two points: 1. Early cutting of the first growth of alfalfa or insecticide treatment will reduce alfalfa weevil populations. 2. 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. ● Also know that 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), parasitizes alfalfa weevil in Alberta and Saskatchewan, and is now found in Manitoba.
Alfalfa Weevil (Hypera postica) – Reminder – 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).
Updated – Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur. Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.
For the week of June 26, 2016, the following map predicts the developmental stages for alfalfa weevil and corresponding degree-days. Areas highlighted orange are predicted to find fourth instar larvae so scout for major leaf feeding then compare larval densities to the action threshold for alfalfa weevil!
Economic thresholds for Alfalfa weevil (adapted from Soroka 2015) vary by crop type (hay or seed), area fed upon and larval densities. 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. ● Also consider these two points: 1. Early cutting of the first growth of alfalfa or insecticide treatment will reduce alfalfa weevil populations. 2. 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. ● Also know that 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), parasitizes alfalfa weevil in Alberta and Saskatchewan, and is now found in Manitoba.
Alfalfa Weevil (Hypera postica) – Please refer to earlier posts to find information related to the appearance, damage and biology of this insect pest.
Updated – Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur. Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.
For the week of July 3, 2016, the following map predicts the developmental stages for alfalfa weevil and corresponding degree-days. Areas highlighted orange are predicted to find fourth instar larvae.
Economic thresholds for Alfalfa weevil (adapted from Soroka 2015) vary by crop type (hay or seed), area fed upon and larval densities. 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. ● Also consider these two points: 1. Early cutting of the first growth of alfalfa or insecticide treatment will reduce alfalfa weevil populations. 2. 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. ● Also know that 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), parasitizes alfalfa weevil in Alberta and Saskatchewan, and is now found in Manitoba.
Alfalfa Weevil (Hypera postica) – 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).
Updated – Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur. Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.
For the week of June 26, 2016, the following map predicts the developmental stages for alfalfa weevil and corresponding degree-days. Areas highlighted orange are predicted to find fourth instar larvae so scout for major leaf feeding then compare larval densities to the action threshold for alfalfa weevil!
Economic thresholds for Alfalfa weevil (adapted from Soroka 2015) vary by crop type (hay or seed), area fed upon and larval densities. 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. ● Also consider these two points: 1. Early cutting of the first growth of alfalfa or insecticide treatment will reduce alfalfa weevil populations. 2. 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. ● Also know that 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), parasitizes alfalfa weevil in Alberta and Saskatchewan, and is now found in Manitoba.
Alfalfa Weevil (Hypera postica)– Earlier predictive model outputs can be reviewed by searching the Blog for “Alfalfa weevil” or use the Label Index located to the right of the screen to sort and review all “Alfalfa weevil” posts for 2016.
Reminder – 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).
Economic thresholds for Alfalfa weevil (adapted from Soroka 2015) vary by crop type (hay or seed), area fed upon and larval densities. 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. ● Also consider these two points: 1. Early cutting of the first growth of alfalfa or insecticide treatment will reduce alfalfa weevil populations. 2. 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. ● Also know that 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), parasitizes alfalfa weevil in Alberta and Saskatchewan, and is now found in Manitoba.
Alfalfa Weevil (Hypera postica) – 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).
Updated – Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur. Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.
For the week of June 12, 2016, thanks to D. Giffen for updating the following map to match the above predicted developmental stages and corresponding degree-days. Areas highlighted yellow are predicted to find second instar larvae the week of June 12th. Areas highlighted gold are predicted to encounter third instar larvae while areas highlighted orange should observe fourth instar larvae so scout for major leaf feeding then compare larval densities to the action threshold for alfalfa weevil!
Economic thresholds for Alfalfa weevil (adapted from Soroka 2015) vary by crop type (hay or seed), area fed upon and larval densities.
In hay fields, forage losses can be economic if one or more of the following syptoms 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. ● Also consider these two points: 1. Early cutting of the first growth of alfalfa or insecticide treatment will reduce alfalfa weevil populations. 2. 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. ● Also know that 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), parasitizes alfalfa weevil in Alberta and Saskatchewan, and is now found in Manitoba.
Alfalfa Weevil (Hypera postica) – 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). Updated – Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur. Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.
For the week of June 5, 2016, second instar larvae are predicted to be present in fields falling within areas of the map highlighted ANY shade of purple. Third and fourth instar larvae are predicted to be present in fields falling within areas highlighted ANY shade of blue in the map below. Scout field and compare larval densities to the action threshold for alfalfa weevil which varies according to end use and crop stage.
Blister Beetles (predator) Last year, the focus of the Insect of the Week was crop pests. This year, we’re changing things up and highlighting the many natural enemies that help you out, silently and efficiently killing off crop pests. [note: featured Insects of the Week in 2015 are available on the Insect of the Week page] This week’s Insect of the Week is the blister beetle (Lytta nuttalli and Epicauta spp.). This is a good news/bad news story. The good news is that the Epicauta spp. larvae feed on grasshopper eggs. But the bad news is that the Nuttall blister beetle larvae feed on ground-dwelling leaf-cutter and bumble bees. The bad news continues: adult blister beetles contain a toxin, cantharidin. When beetles get baled in with alfalfa hay, the toxin can cause severe distress in livestock, especially horses.
See more information in the new Field Crop and Forage Pests and their Natural Enemies in Western Canada – Identification and Management Field Guide for identification, life cycle and conservation options (download links for field guide available on the Insect of the Week page).
Alfalfa Weevil (Hypera postica) – 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). Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur. Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.
This week, alfalfa growers situated within ANY shade of purple should prioritize scouting for second instar larvae and compare it to the action threshold for alfalfa weevil which varies according to end use and crop stage.
Use the figure below as a visual reference to identify alfalfa weevil larvae. Note the white dorsal line, the tapered shape and the dark head capsule.
Pea leaf weevil (Sitona lineatus) – Be aware that higher densities of pea leaf weevil and higher levels of feeding damage have been observed in 2016 compared to 2015. The 2015 pea leaf weevil risk map, based on damage observed on peas, is below as reference.
Review the updates provided by Carcamo for southern Alberta and Hartley related to southwest Saskatchewan posted last week.
Reminder – Pea leaf weevils emerge in the spring primarily by flying (at temperatures above 17ºC) or they may walk short distances. Pea leaf weevil movement into peas and faba beans is achieved primarily through flight. Adults are slender, greyish-brown measuring approximately 5 mm in length (Figure 1).
Figure 1. The pea leaf weevil, Sitona lineatus, measures ~5mm long (Photo: H. Goulet).
The pea leaf weevil resembles the sweet clover weevil (Sitona cylindricollis) yet the former is distinguished by three light-coloured stripes extending length-wise down thorax and sometimes the abdomen (Link here for the Pea leaf weevil monitoring protocol with photos of related weevils). All species of Sitona, including the pea leaf weevil, have a short snout. Adults will feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas) and produce a characteristic, scalloped (notched) edge (Figure 2). Females lay 1000 to 1500 eggs in the soil either near or on developing pea or faba bean plants from May to June.
Figure 2. Feeding notches on clam leaf of pea plant resulting from pea leaf weevil (Photo: L. Dosdall).
Alfalfa Weevil (Hypera postica) – 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).
Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models. The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur. Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.
This week, alfalfa growers situated within ANY shade of purple should prioritize scouting for second instar larvae and compare it to the action threshold for alfalfa weevil which varies according to end use and crop stage.
Pea leaf weevil (Sitona lineatus) – Pea leaf weevils emerge in the spring primarily by flying (at temperatures above 17ºC) or they may walk short distances. Pea leaf weevil movement into peas and faba beans is achieved primarily through flight. Adults are slender, greyish-brown measuring approximately 5 mm in length (Figure 1).
Figure 1. The pea leaf weevil, Sitona lineatus, measures ~5mm long (Photo: H. Goulet).
The pea leaf weevil resembles the sweet clover weevil (Sitona cylindricollis) yet the former is distinguished by three light-coloured stripes extending length-wise down thorax and sometimes the abdomen (Link here for the Pea leaf weevil monitoring protocol with photos of related weevils). All species of Sitona, including the pea leaf weevil, have a short snout.
Adults will feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas) and produce a characteristic, scalloped (notched) edge (Figure 2). Females lay 1000 to 1500 eggs in the soil either near or on developing pea or faba bean plants from May to June.
Figure 2. Feeding notches on clam leaf of pea plant resulting from pea leaf weevil (Photo: L. Dosdall).
More information about Wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”. View ONLY the Lygus bug pages, or Alfalfa plant bug, or Superb plant bug pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.
Reminder – Pea Leaf Weevil (Sitona lineatus) – Pea leaf weevils emerge in the spring primarily by flying (at temperatures above 17ºC) or they may walk short distances. Pea leaf weevil movement into peas and faba beans is achieved primarily through flight. Adults are slender, greyish-brown measuring approximately 5 mm in length. The pea leaf weevil resembles the sweet clover weevil (Sitona cylindricollis) yet the former is distinguished by three light-coloured stripes extending length-wise down thorax and sometimes the abdomen (Access the Pea leaf weevil monitoring protocol). All species of Sitona, including the pea leaf weevil, have a short snout.
Adults will feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas) and produce a characteristic, scalloped (notched) edge. Females lay 1000 to 1500 eggs in the soil either near or on developing pea or faba bean plants from May to June.
Information related to Pea leaf weevil in Alberta and the forecast for 2016 is posted here.
