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).
Compared to long-term averages, bertha armyworm (BAW) development has been delayed thus far in the 2022 growing season. Pupal BAW development is progressing across the prairies. This week, pupal development is predicted to complete and adult emergence is expected to occur across most of the prairies (Fig. 1). Adult emergence should have already begun across a region extending from Lethbridge to Regina and north to Saskatoon. Adult emergence near Regina, Saskatchewan (Fig. 2) is predicted to be one week ahead of central Alberta (Fig. 3). Oviposition should begin over the next 7-10 days.
Figure 1. Predicted bertha armyworm (Mamestra configurata) pupal development (%) across the Canadian prairies as of June 19, 2022.Figure 2. Predicted bertha armyworm (Mamestra configurata) populations near Regina, Saskatchewan as of June 19, 2022(projected to June 30, 2022, based on long-term average conditions). Figure 3. Predicted bertha armyworm (Mamestra configurata) populations near Lacombe, Alberta as of June 19, 2022(projected to June 30, 2022, based on long-term average conditions).
Use the images below (Fig. 4) to help identify moths from the by-catch that will be retained in the green phermone-baited unitraps.
Figure 4. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada)
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also, refer to the bertha armyworm pages within 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 to June 6, 2021, indicate that bertha armyworm (BAW) (Mamestra configurata) pupal development ranges from 60-90 % across the prairies (Fig. 1). BAW traps should be placed in fields when pupal development exceeds 80 %. Table 1 provides guidelines to determine when traps should be deployed. Based on weather data up to June 6, 2021, BAW adults should begin to emerge by mid to late June.
Figure 1. Predicted bertha armyworm (Mamestra configurata) pupal development across the Canadian prairies as of June 6, 2021.
Model projections to June 30 predict that development near Winnipeg will be more advanced than at Lacombe (Figs. 2 and 3, respectively). The model predicts that egg hatch will begin in mid-June near Winnipeg.
Figure 2. Predicted development of bertha armyworm (Mamestra configurata) populations near Winnipeg, Manitoba as of June 6, 2021 (projected to June 30, 2021).Figure 3. Predicted development of bertha armyworm (Mamestra configurata) populations near Lacombe, Alberta as of June 6, 2021 (projected to June 30, 2021).
Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also, refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
This week’s “Insect of the Week” is the Pea Leaf Weevil. Larval hosts are field peas and faba beans. Adults can spread to other cultivated and wild legumes, such as alfalfa, beans and lentils. Each adult female lays up to 300 eggs in one summer! The eggs hatch in the soil near developing plants and larvae move to feed on nitrogen-fixing nodules. This results in partial or complete inhibition of nitrogen fixation by the plant, causing poor plant growth. Adults feed on leaves and growing points of seedlings, causing notches in leaf margins.
Adult pea leaf weevil damage, showing crescent shaped notches on the leaf margin (AAFC)
The pea leaf weevil is a slender greyish-brown insect measuring approximately 5 mm in length. These insects can be distinguished by three light-coloured stripes extending length-wise down the thorax and sometimes the abdomen. All species of Sitona, including the pea leaf weevil, have a short snout. Mature larva grow up to 3.5-5.5 mm long, and are legless and c-shaped with a brown head.
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).
Early in the growing season many of the native and introduced species of ladybird beetles become active and are easily observed (Fig. 1). These adults give rise to a whole new legion of voracious larvae and adults so preserve and protect them in fields – it could pay off!
Figure 1. Ladybird beetle (Coleoptera: Coccinellidae) hunting on wheat head (photo: AAFC-Otani).
Coccinellids are recognized as general predators with a real taste for aphids. Many species exist in North America but introduced species (either released or adventively establishing on this continent) have displaced many native species. With such a fantastic array of colours, sizes, shapes, and spots, we’re providing a few resources to help you recognize the amazing diversity in fields: ● Access “Bug Guide” and their entries falling within the Family Coccinellidae. ● “Key to the lady beetles of Saskatchewan“, released by D.J. Larson in 2013 – a technical key that includes colour photos of ladybird beetle adults. Species included in this key will most closely resemble what’s present across the Canadian prairies. ● “Ladybugs of South Dakota” is a PDF visual example of several species of coccinellids, some of which will also occur on the Canadian prairies. The poster was produced in conjunction with the “Lost Ladybug Project” and other supporting institutions. ● Consider participating in citizen-science – the Lost Ladybug Project has been in place for many years but the group welcomes reports of coccinellids from anywhere in North America and helps identify from submitted photos. The goal is to keep track of native species in comparison to the helpful but fairly competitive introduced species like Coccinella semptempunctata or Harmonia axyridis (Pallas). ● The Canadian portal of iNaturalist.ca was launched in 2015 and is connected to iNaturalist.org but the premise is the same: By signing up and submitting photos with relevant brief observations (e.g., date, location, e-contact info), users can communicate online with creditable and knowledgeable resources that help identify flora and fauna. Watch their YouTube video to learn more. Download the App (Android Google Play OR iOS App Store).
As of August 17, 2020, the Pea leaf weevil (PLW) model indicates that pupation is complete and adults are beginning to emerge from pea fields. The PLW model predicts that warm, dry conditions in June and early July may reduce larval survival. Wetter conditions during June and July were more favourable for PLW population development in Alberta than in eastern Saskatchewan and Manitoba. These factors resulted in lower overwintering adult index values for the eastern prairie region than for western regions (Fig. 1). Figure 2 represents the expected overwintering index values for PLW using climate normal data. Note that, to our knowledge, populations of pea leaf weevil remain low in Manitoba and are confined to the Swan River Valley region at this time.
Figure 1. The predicted overwintering adult index of pea leaf weevil (Sitona lineatus) across the Canadian prairies as of August 17, 2020.Figure 2. The predicted overwintering adult index of pea leaf weevil (Sitona lineatus) across the Canadian prairies as of August 17, 2020, using climate normal data.
The pea leaf weevil is a slender greyish-brown insect measuring approximately 5 mm in length (Fig. 3, 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
Review a more complete description of this insect posted back on Week 11 of the 2020 growing season. Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Ladybird beetle larvae (Fig. 1), pupae (Fig. 2), and adults (Fig. 3) can all be found in fields at this time of year. Take a look at the various stages and the many patterns of native and introduced species to recognize these as Field Heroes! Ladybird beetles are categorized as general predators and will feed on several species of arthropods but are partial to aphids.
Figure 4. An aphid “mummy” adhered to a wheat awn. A “mummy” is the aphid host transformed to enclose a soon-to-emerge parasitoid wasp (photo credit: AAFC-Beaverlodge).
Models runs predicting spring adult activity, oviposition and larval development for this pest are completed as of Week 9 (June 21, 2020). Use the following information to aid in-field scouting for larvae.
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 (Left).
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.
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 2). 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 3) results in partial or complete inhibition of nitrogen fixation by the plant and results in poor plant growth and low seed yields.
Figure 2. Larva of pea leaf weevil in soil (Photo: L. Dosdall).Figure 3. Damaged pea nodules (Photo: L. Dosdall).
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – Model runs for Red Deer and Saskatoon were projected to June 30, 2019. Results indicated that oviposition is well underway at both locations.
Figure 1. Predicted status of pea leaf weevil populations near Red Deer AB projected to June 30, 2019, using long term average temperatures. Figure 2. Predicted status of pea leaf weevil populations near Saskatoon SK projected to June 30, 2019, using long term average temperatures.
This week, pea leaf weevil and its doppelgangers were featured as part of the INSECT OF THE WEEK.
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.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
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.
Pea Leaf Weevil (Sitona lineatus) – Model runs for Red Deer AB (Fig. 1) and Swift Current SK (Fig. 2) were projected to June 15, 2019. Results indicated that oviposition should begin early next week. Model predictions, based on long term normal weather data predict that initial hatch near Saskatoon should occur on May 29th.
Figure 1. Projected predicted status of pea leaf weevil populations near Red Deer AB to June 15, 2019 using long term average temperatures. Figure 2. Projected predicted status of pea leaf weevil populations near Swift Current SK to June 15, 2019 using long term average temperatures.
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 (Fig. 3, Left).
The 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – Model runs for Red Deer AB (Fig. 1) and Swift Current SK (Fig. 2) were projected to June 15, 2019. Results indicated that oviposition should begin at the end of May. Model predictions, based on long term normal weather data, predict that initial hatch near Saskatoon should occur on May 29th.
Figure 1. Projected predicted status of pea leaf weevil populations near Red Deer AB to June 15, 2019 using long term average temperatures. Figure 2. Projected predicted status of pea leaf weevil populations near Swift Current SK to June 15, 2019 using long term average temperatures.
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 (Fig. 3, Left).
The 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – Model runs for Red Deer AB (Fig. 1) and Swift Current SK (Fig. 2) were projected to June 15, 2019. Results indicated that oviposition should begin at the end of May. Model predictions, based on long term normal weather data, predict that initial hatch near Saskatoon should occur on May 29th.
Figure 1. Projected predicted status of pea leaf weevil populations near Red Deer AB to June 15, 2019 using long term average temperatures. Figure 2. Projected predicted status of pea leaf weevil populations near Swift Current SK to June 15, 2019 using long term average temperatures.
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 (Fig. 3, Left).
The 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – The PLW model was run for Red Deer AB (Fig. 1) and Saskatoon SK (Fig. 2). The predictive model outputs suggest that PLW adults are active but oviposition has not begun.
Figure 1. Predicted status of pea leaf weevil populations near Red Deer as of May 7, 2019. Figure 2. Predicted status of pea leaf weevil populations near Saskatoon SK as of May 7, 2019.
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 (Fig. 3, Left).
The 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – The PLW model was run for Red Deer AB (Fig. 1) and Saskatoon SK (Fig. 2). The output suggests that PLW are beginning to become active and will begin to fly on warmer days (Figs. 1 and 2).
Figure 1. Predicted overwintered PLW adults near Red Deer AB as of April 30, 2019. Figure 2. Predicted overwintered PLW adults near Saskatoon SK as of April 30, 2019.
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 (Fig. 3, Left).
The 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – The PLW model was run for Lethbridge AB (Fig. 1) and Saskatoon SK (Fig. 2). Output suggests that PLW are beginning to become active.
Figure 1. Predicted PLW phenology at Lethbridge AB based on long term climate data. Values are based on model simulations (April 1 – April 23, 2019).Figure 2. Predicted PLW phenology at Saskatoon SK based on long term climate data. Values are based on model simulations (April 1 – April 23, 2019).
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 (Fig. 3, Left).
The 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 3 Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Reminder – The risk map for pea leaf weevils was released in March 2019. The map is based on the number of feeding notches observed in peas (Fig. 4).
Figure 4. Estimates of pea leaf weevil (S. lineatus) densities based on feeding notches observed in peas grown in Alberta and Saskatchewan in 2018.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Reminder – While scouting, you may encounter these fascinating organisms…..
Figure 1. Ladybird beetle larva (photo credit: AAFC-Beaverlodge)Figure 2. Ladybird beetle pupa (Left) and larva (Right) (photo credit: AAFC-Beaverlodge)Figure 3. Ladybird beetle pupa (photo credit: AAFC-Beaverlodge)Figure 4. Ladybird beetle (Coccinella septempunctata) (photo credit: AAFC-Beaverlodge)Figure 5. Aphids nestled on wheat head (photo credit: AAFC-Beaverlodge)Figure 6. An aphid “mummy” adhered to a wheat awn. Mummy is the aphid host converted to enclose a soon-to-emerge parasitoid wasp (photo credit: AAFC-Beaverlodge)
Ladybird beetle larvae (Fig. 1-2), pupae (Fig. 2-3), and adults (Fig. 4) can all be found in fields at this time of year. Take a look at the various stages and the many patterns of native and introduced species to recognize these as Field Heroes! Ladybird beetles are categorized as general predators and will feed on several species of arthropods but are partial to aphids (Fig. 5).
While scouting, you may encounter these fascinating organisms…..
Figure 1. Ladybird beetle larva (photo credit: AAFC-Beaverlodge)Figure 2. Ladybird beetle pupa (Left) and larva (Right) (photo credit: AAFC-Beaverlodge)Figure 3. Ladybird beetle pupa (photo credit: AAFC-Beaverlodge)Figure 4. Ladybird beetle (Coccinella septempunctata) (photo credit: AAFC-Beaverlodge)Figure 5. Aphids nestled on wheat head (photo credit: AAFC-Beaverlodge)Figure 6. An aphid “mummy” adhered to a wheat awn. Mummy is the aphid host converted to enclose a soon-to-emerge parasitoid wasp (photo credit: AAFC-Beaverlodge)
Ladybird beetle larvae (Fig. 1-2), pupae (Fig. 2-3), and adults (Fig. 4) can all be found in fields at this time of year. Take a look at the various stages and the many patterns of native and introduced species to recognize these as Field Heroes! Ladybird beetles are categorized as general predators and will feed on several species of arthropods but are partial to aphids (Fig. 5).
Pea Leaf Weevil (Sitona lineatus) – Over the past ten days newly emerged adult pea leaf weevils are predicted to be emerging from pea crops (Fig. 1).
Figure 1. Predicted pea leaf weevil phenology at Saskatoon (A) and Lethbridge (B). Values are based on model simulations for the current growing season (April 1 – July 30, 2018).
Pea leaf weevil larvae develop under the soil over a period of 30 to 60 days. They are “C” shaped with a dark brown head capsule. The rest of the body is a milky-white color (Fig. 2 A). Larvae develop through five instar stages. In the 5th instar, larvae range in length from 3.5 – 5.5 mm. First instar larvae bury into the soil after hatching, and search out root nodules on field pea and faba bean plants. Larvae enter and consume the microbial contents of the root nodules (Fig. 2 B). These root nodules are responsible for nitrogen-fixation, thus pea leaf weevil larval feeding can affect plant yield and the plant’s ability to input nitrogen into the soil.
Figure 2. Pea leaf weevil larva in soil (A) and field pea root nodules damaged by larval feeding (B). Photos: L. Dosdall).
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
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.
Pea Leaf Weevil (Sitona lineatus) – As of June 24, 2018, the PLW model predicted that hatch is nearly complete and the population is primarily in the larval stage in the Saskatoon area (Fig. 1). Development in 2018 is faster than long term average (Fig. 2).
Figure 1. Predicted pea leaf weevil phenology at Saskatoon SK. Values are based on model simulations for April 1 – June 24, 2018.Figure 2. Predicted pea leaf weevil phenology at Saskatoon SK. Values are based on model simulations for Long Term Climate Normals (LTCN).
Pea leaf weevil larvae develop under the soil over a period of 30 to 60 days. They are “C” shaped with a dark brown head capsule. The rest of the body is a milky-white color (Fig. 3 A). Larvae develop through five instar stages. In the 5th instar, larvae range in length from 3.5 – 5.5 mm. First instar larvae bury into the soil after hatching, and search out root nodules on field pea and faba bean plants. Larvae enter and consume the microbial contents of the root nodules (Fig. 3 B). These root nodules are responsible for nitrogen-fixation, thus pea leaf weevil larval feeding can affect plant yield and the plant’s ability to input nitrogen into the soil.
Figure 3. Pea leaf weevil larva in soil (A) and field pea root nodules damaged by larval feeding (B). Photos: L. Dosdall).
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – The PLW model predicted that larvae should be appearing in fields near Saskatoon (Fig. 1). Development in 2018 is faster than that predicted using long term averages (LTCN presented in Fig. 2).
Figure 1. Predicted pea leaf weevil phenology at Saskatoon SK. Values are based on model simulations for April 1 – June 18, 2018.Figure 2. Predicted pea leaf weevil phenology at Saskatoon SK. Values are based on model simulations for April 1 – June 18, 2018. using Long Term Climate Normals.
Larvae develop under the soil over a period of 30 to 60 days. They are “C” shaped with a dark brown head capsule. The rest of the body is a milky-white color (Fig. 3 A). Larvae develop through five instar stages. In the 5th instar, larvae range in length from 3.5 – 5.5 mm. First instar larvae bury into the soil after hatching, and search out root nodules on field pea and faba bean plants. Larvae enter and consume the microbial contents of the root nodules (Fig. 3 B). These root nodules are responsible for nitrogen-fixation, thus pea leaf weevil larval feeding can affect plant yield and the plant’s ability to input nitrogen into the soil.
Figure 3. Pea leaf weevil larva in soil (A) and field pea root nodules damaged by larval feeding (B). Photos: L. Dosdall).
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – The PLW model predicts that oviposition is nearly complete and PLW are primarily in the adult and egg stages (Fig. 1). Larvae should begin to appear later this week.
Figure 1. Predicted pea leaf weevil phenology at Red Deer AB. Values are based on model simulations, for April 1-May 28, 2018 (projected to July 15, 2018).
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 (view weevil adult photos here).
Adults 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. 4). Females lay 1000 to 1500 eggs in the soil either near or on developing pea or faba bean plants from May to June.
Figure 4. Scalloped notching along leaf margins of pea plant (Photo: L. Dosdall).
Larvae develop under the soil over a period of 30 to 60 days. They are “C” shaped with a dark brown head capsule. The rest of the body is a milky-white color (Fig. 5 A). Larvae develop through five instar stages. In the 5th instar, larvae range in length from 3.5 – 5.5 mm. First instar larvae bury into the soil after hatching, and search out root nodules on field pea and faba bean plants. Larvae enter and consume the microbial contents of the root nodules (Fig. 5 B). These root nodules are responsible for nitrogen-fixation, thus pea leaf weevil larval feeding can affect plant yield and the plant’s ability to input nitrogen into the soil.
Figure 5. Pea leaf weevil larva in soil (A) and field pea root nodules damaged by larval feeding (B). Photos: L. Dosdall).
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – The PLW model predicts that oviposition is occurring across southern and central regions of the prairies (example Red Deer (Fig. 9).
Figure 1. Predicted pea leaf weevil phenology at Red Deer AB. Values are based on model simulations, for April 1-May 28, 2018 (projected to July 15, 2018).
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 (Fig. 2, Left).
The 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 2. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Reminder – The 2017 risk map for pea leaf weevils was released in March 2018. The map is based on the number of feeding notches observed in peas (Fig. 3).
Figure 3. Estimates of pea leaf weevil (S. lineatus) densities based on feeding notches observed in peas grown in Alberta and Saskatchewan in 2017.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – The PLW model predicts that oviposition is occurring across southern and central regions of the prairies (example Swift Current – Fig. 1).
Figure 1. Predicted pea leaf weevil phenology at Swift Current SK.
Values are based on model simulations (April 1-May 28, 2018 and projected to July 1, 2018).
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 (Fig. 2, Left). The 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 2. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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. Reminder – The 2017 risk map for pea leaf weevils was released in March 2018. The map is based on the number of feeding notches observed in peas (Fig. 3).
Figure 3. Estimates of pea leaf weevil (S. lineatus) densities based on feeding notches observed in
peas grown in Alberta and Saskatchewan in 2017.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – The PLW model predicts that adult weevils should be out and that oviposition may be occurring in fields with emerging peas. An example of PLW predicted phenology for Swift Current SK is presented in Figure 1.
Figure 1. Predicted PLW phenology at Swift Current, SK. Values are based on model simulations,
for April 1 – May 21, 2018 (projected to July 1, 2018).
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 (Fig. 2, Left). The 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 2. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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. Reminder – The 2017 risk map for pea leaf weevils was released in March 2018. The map is based on the number of feeding notches observed in peas (Fig. 3).
Figure 3. Estimates of pea leaf weevil (S. lineatus) densities based on feeding notches observed in
peas grown in Alberta and Saskatchewan in 2017.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – The PLW model predicts that adults are beginning to fly. This is similar to model output based on long term (climate) data. Model output estimates that oviposition should begin in late May or early June (Fig. 1).
Figure 1. Predicted PLW phenology at Swift Current based on long term climate data.
Values are based on model simulations (April 1 – May 6).
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 (Fig. 2, Left). The 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 2. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Reminder – The 2017 risk map for pea leaf weevils was released in March 2018. The map is based on the number of feeding notches observed in peas (Fig. 3).
Figure 3. Estimates of pea leaf weevil (S. lineatus) densities based on feeding notches observed in
peas grown in Alberta and Saskatchewan in 2017.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
Pea Leaf Weevil (Sitona lineatus) – The PLW model predicts that adults are emerging from overwintering sites and beginning to fly. This is similar to model output based on long term (climate) data. Looking forward, based on long term average climate data, oviposition should occur in late May or early June (Fig. 1).
Figure 1. Predicted PLW phenology at Swift Current based on long term climate data. Values are
based on model simulations (April 1 – May 6).
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 (Fig. 1, Left). The 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 (Left).
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.
Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.
This week’s Insect of the Week is the brown marmorated stink bug (Halyomorpha halys). Stink bugs get their name from the foul odour they release when threatened. Nymphs and adults prefer field corn and soybean, but infestations have been reported on rape, pea, sunflower and cereals in the USA. They have also been known to attack tree fruits, berries, vegetables and many ornamental trees and shrubs. They are not known to be established in the Prairies, but have been found in the BC Southern Interior, Ontario and Quebec. Feeding causes damage to seeds and seed pods, reducing yield.
Brown marmorated stink bug – adult (CC-BY 2.0 Katja Schulz)
Pea Leaf Weevil (Sitona lineatus) – Oviposition is predicted to have peaked across central and southern regions of Alberta and Saskatchewan. Hatch should be underway in pea fields near Lethbridge while hatching is predicted to occur this week near Saskatoon.
Pea Leaf Weevil (Sitona lineatus) – This week, weevil oviposition is predicted to be occurring across central and southern regions of Alberta and Saskatchewan.
The PLW Blitz continues this week and features: – The Insect of the Week from June 1st, – ANEWLY UPDATED Monitoring Protocol (Vankosky et al. 2017), AND – The current Insect of the Week features a group of beetles recognized as general predators but one species is an egg predator associated with Pea leaf weevil.
Remember – 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 (Fig. 3, Left). The 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
Adults 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. 4). Females lay 1000 to 1500 eggs in the soil either near or on developing pea or faba bean plants from May to June.
Figure 4. Scalloped notching along leaf margins of pea plant (Photo: L. Dosdall).
This week’s “Insect of the Week” is the Pea Leaf Weevil. Larval hosts are field peas and faba beans. Adults can spread to other cultivated and wild legumes, such as alfalfa, beans and lentils. Each adult female lays up to 300 eggs in one summer! The eggs hatch in the soil near developing plants and larvae move to feed on nitrogen-fixing nodules. This results in partial or complete inhibition of nitrogen fixation by the plant, causing poor plant growth. Adults feed on leaves and growing points of seedlings, causing notches in leaf margins.
Adult, larval and egg stages overlap and all three can be present over most of the growing season. For more information about Pea Leaf Weevil risk in your area, see the 2017 Insect Risk Maps page. Also, we have posted a NEW Pea Leaf Weevil monitoring protocol.
For more information on the pea leaf weevil, see the Insect of the Week page.
Pea leaf weevil – adult, eggs (Mike Dolinski, MikeDolinsky@hotmail.com)
Pea Leaf Weevil (Sitona lineatus) – This week is our PLW Blitz featuring this pest with: -The Insect of the Week, -Updated model outputs and phenological predictions for 2017 (as of May 29, 2017), and – A NEWLY UPDATED Monitoring Protocol (Vankosky et al. 2017)!
The PLW model was run for Lethbridge AB and Saskatoon SK.Current weather data was used then extended by Long Term Normal climate data (May 30-Jun 30) in order to predict pea leaf weevil phenology. Compared to last week, model output indicated that oviposition has been delayed by ~5-7 days. As of May 29th, phenologies for eggs and larvae were predicted to be similar for both locations (Fig. 1-2).
Figure 1. Pea leaf weevil model predicting phenology for 2017 near Saskatoon SK.
Figure 2. Pea leaf weevil model predicting phenology for 2017 near Lethbridge AB.
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 (Fig. 3, Left). The 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Pea Leaf Weevil (Sitona lineatus) – The pea leaf weevil simulation model will be used to monitor weevil development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of weevil development stages based on biological parameters for Sitona lineatus.
The PLW model was run for Lethbridge AB and Saskatoon SK. Meteorological data (April 1 – May 15, 2017) and climate data (May 16- June 30) were used to predict PLW phenology. Output indicates that PLW oviposition in Lethbridge is approximately one week earlier than Saskatoon.Reminder – Access last week’s PLW model output predictions here.
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 (Fig. 1, Left). The 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Pea Leaf Weevil (Sitona lineatus) – The pea leaf weevil simulation model will be used to monitor weevil development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of weevil development stages based on biological parameters for Sitona lineatus.
Model output predicted that flight of pea leaf weevil adults was significantly earlier in Lethbridge than Saskatoon in 2017. In the figure below, note the red line predicting adults emerging from overwintering then the yellow line predicting overwintered adults taking flight this spring for Lethbridge AB (Fig. 1, Upper) and Saskatoon SK (Fig. 1, Lower).
Figure 1. Model output predicting development of pea leaf weevil in Lethbridge AB (Upper) and Saskaton SK (Lower) in the spring of 2017.
Reminder – In 2016, the distribution of pea leaf weevil increased dramatically based on both damage assessments AND collection of adults in 2016 (Fig. 2).
Figure 2. Distribution of pea leaf weevil (Sitona lineatus) based on surveying conducted in 2016 (Olfert et al. 2017).
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 (Fig. 3, Left). The 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
Pea Leaf Weevil (Sitona lineatus) – This species was one of the “big” insects of 2016’s field crop growing season. The distribution of pea leaf weevil increased dramatically based on both damage assessments AND collection of adults in 2016 (Fig. 1) compared to previous years (Fig. 2).
Figure 1. Distribution of pea leaf weevil (Sitona lineatus) based on surveying conducted in 2016 (Olfert et al. 2017).
Figure 2. Distributions of pea leaf weevil based on surveying conducted between 2012-2015 (Olfert et al. 2017).
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 (Fig. 3, Left). The 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 3. Comparison images and descriptions of four Sitona species adults including pea leaf weevil (Left).
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.
The 2017 Prairie-Wide Risk and Forecast Maps can be viewed and downloaded here. Maps are generated for bertha armyworm, grasshoppers, wheat midge, cabbage seedpod weevil, pea leaf weevil, wheat stem sawfly, diamondback moth as well as average temperature, average precipitation, and modeled soil moisture for the Canadian prairies.
Thank you to the many people who monitor each growing season! An astonishing 6414 survey stops were involved in the insect monitoring performed across the Canadian prairies in 2016!
Small scarab beetle (Coleoptera: Aphodius distinctus) – This is the time of summer that farmers will be seeing larvae of a small scarab beetle (Aphodius distinctus) in their fields. There have been scattered reports each June of large numbers of beetle grubs in crops associated with crop damage (e.g., canola, corn, dry bean, onion, pea).
Please help researchers compile information related to this species so they might confirm its pest status! Information is posted about the beetle and the survey. Here’s how you can help:
1. Please send reports of high white grub densities and associated crop damage to Kevin.Floate@agr.gc.ca (403-317-2242).
2. Live larvae accompanied by the following field information would be extremely helpful please – contact Dr. Kevin Floate if you have a sample!
3. Include answers to the following so the pest status for this species can be ascertained: – Previous crop? –Legal land location or latitude+longitude? –Irrigated or not? –Was composted manure added this spring? –Surface residue in spring?
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).
Pea leaf weevil monitoring is underway in Alberta and Saskatchewan. Despite the common name, Sitona lineolatus, will feed on several species of legumes including faba beans, seedling alfalfa, dry beans and of course peas!
Thanks to Dr. Hector Carcamo (AAFC-Lethbridge) for the following update (24May2016): A mild winter and a very warm and early spring have contributed to what looks like the worst outbreak of pea leaf weevil in southern Alberta. Weevil densities appear to be high enough to be threatening stand establishment of peas this year.
Normally, adult feeding damage has little consequence whereas the main concern is related to larval feeding damage to nitrogen fixing nodules. That’s NOT the case this year – several growers are spraying for PLW in peas because small seedlings are suffering very high defoliation resulting in stand reductions – something seen previously only in seedling alfalfa stands. Additionally, this year some stands treated with a registered neonicotinoid insecticide have required foliar spraying; the insecticide seed treatment may not provide sufficient protection when weevil densities are extremely high. Growers hoping to prevent yield losses may consider supplementing with nitrogen during the seedling stage but be cautious – the economic returns should be carefully considered, given input prices. Finally, be mindful that PLW adults emerge from overwintering over several weeks so sprayed fields may be repeatedly invaded – continued monitoring is a necessity!
Weevils have natural enemies such as ground dwelling beetles that feed on their eggs. The best way to protect natural enemies is to avoid foliar applications of insecticide unless damage reaches the economic threshold of 30% of seedlings with damage on the clam leaf (i.e., assess using 10 transects of 10 seedlings, half near the edge and half inside the field).
Thanks to Scott Hartley (Sask Ag) who noted (25May2016) that PLW surveying is underway in the southwestern Saskatchewan (i.e., as far north as Kindersley / Outlook and east to mid-way between Swift Current and Moose Jaw). Preliminary reports include high levels of feeding in several areas in the southwest. Crops were generally seeded earlier this year than in the past few years. Seed treatments are considered the best control for the pea leaf weevil but, if 30% of plants are showing damage, a foliar insecticide could be required but this strategy is not as consistently effective as a seed treatment. Foliar insecticide may be necessary if plants are very young and therefore more vulnerable to heavy feeding pressure. Remember plants can outgrow PLW damage once they are past the 6th node 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).
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.
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.
