Weekly Update (July 23, 2020; Wk 13)

Going, going, gone - we are over on the NEW WEBSITE and this is the last Post on this Blog!

Re-subscribe to the new website to continue to receive all the Prairie Pest Monitoring Network's information in your Inbox!

Going forward, www.prairiepest.ca has all the same great information in a new format:

• WEEKLY UPDATE
• INSECT OF THE WEEK
• ANNUAL RISK AND FORECAST MAPS
• INSECT MONITORING PROTOCOLS
• and more......

A big 'Thank You' to all the folks who have enabled the PPMN Blog to metamorphose to Website status!  NO new information will be posted to this Blog after July 10, 2020.

Weekly Update (July 16, 2020; Wk 12)

A big 'Thank You' to all the moving parts and many people that have enabled the PPMN Blog to metamorphose to Website status!  NO new information will be posted to the Blog after July 10, 2020.

Until the end of July, we will provide a link to access the WEEKLY UPDATE so please go Re-subscribe at the new website to keep receiving in August!

Learn more about the new Prairie Pest Monitoring Network website AND how to re-subscribe to continue to receive the Weekly Update in your Inbox!

Stay Safe and come join us at https://prairiepest.ca/ !!

Questions or problems accessing the contents of this Weekly Update?  Please e-mail Meghan.Vankosky@canada.ca or Jennifer.Otani@canada.ca.  Past “Weekly Updates” can be accessed on our Weekly Update page.

Insect Pest of the Week and the Entomologists that Study Them (July 13): Alfalfa Pests / Feature entomologist: Tyler Wist

Last week, the Prairie Pest Monitoring Network moved over to our NEW WEBSITE!  Click here to read our big news! Same great information and a new format with larger storage capacity.  Find the Insect of the Week Feature for Week 12 (Jul 13) over at our new home!

And remember to re-subscribe to the NEW Website to continue to receive all PPMN Updates in your Inbox!



Visit the INSECT OF THE WEEK and WEEKLY UPDATES webpages!

Weekly Update (July 9, 2020; Wk 11) Otani, Weiss, Trudel, Rounce, Giffen, Svendsen, Olivier, Turkington, Olfert, Vankosky

A VERY EXCITING WEEK - We are taking our new logo and MOVING!

Learn more about new Prairie Pest Monitoring Network website AND how to re-subscribe!

Please access the same WEEKLY UPDATE supporting your in-field insect monitoring efforts by clicking the "JULY 9 (WEEK 11)" on our new Weekly Update webpage.

Alternatively, and only for this week, access a list of hyperlinks to each segment of Week 11 at the new website (to ease the transition)!

A big 'Thank You' to all the moving parts and many people that have enabled the PPMN Blog to metamorphose to Website status!  NO new information will be posted to the Blog after this week (July 10, 2020).

Stay Safe and come join us at https://prairiepest.ca/ !!

Questions or problems accessing the contents of this Weekly Update?  Please e-mail Meghan.Vankosky@canada.ca or Jennifer.Otani@canada.ca.  Past “Weekly Updates” can be accessed on our Weekly Update page.

We're moving!

The Prairie Pest Monitoring Network is excited to announce we have moved to our fresh new website (with a lot of help from our friends)! www.prairiepest.ca 

Important - Re-Subscribe to receive our Weekly Updates
Visit our new site and signup to receive the timely insect pest information you’ve come to expect from us, as well as the Insect of the Week, delivered to your inbox. [Due to Canada's Anti-Spam Legislation and just plain good manners, we cannot copy your subscription to the Blog over to our new website.]

Same great information
The new website is organized like the Blog to keep information including monitoring protocols and risk maps easy to find. But, the website is a work in progress so some information might not be available there yet. Rest assured, the PPMN Blog will stick around so you can look through our past posts and find other information; however, no new information will be posted there after this week (July 10, 2020).

You made us a success
Thank you for using the Blog since it was launched in 2015! We are able to transition to a website now because the Blog is so popular. The new website overcomes some of the Blog shortcomings (e.g., data storage limits). In the future, we hope to introduce new tools to improve insect pest monitoring and insect pest management. Over the coming months, we will work to add information, pictures and links.

Weekly Update links to the NEW website

Click each topic below to access the entire WEEKLY UPDATE (June 9, 2020 for Week 11) over at the NEW WEBSITE!

• Welcome to our new website!
• Weather synopsis
• Predicted wheat midge development
• Predicted grasshopper development
• Bertha armyworm monitoring
• Diamondback moth
• Pea leaf weevil
• Cereal aphid manager
• West nile virus risk
• Scouting charts for canola and flax
• Field heroes
• Provincial insect pest reports
• Crop reports
• Previous posts
• Insect of the Week: Forage grass pests / Dr. Chrystel Olivier
• AND CONGRATULATIONS to the Prairie Crop Disease Monitoring Network on their new Blog!

Insect Pest of the Week and the Entomologists that Study Them (July 6): Forage Grass Pests / Feature entomologist: Chrystel Olivier

This week’s Insect of the Week feature crop is forage grasses: common Prairie plants know to be robust, adaptive, and tolerant to grazing. Our feature entomologist this week is Chrystel Olivier.

Crested wheatgrass cc by 2.0 Matt Lavin

Note: 

This year, we're doing things a bit differently for our Insect of the Week. Instead of focussing on a single insect (pest or natural enemy), we're looking at it from a crop perspective. Each week, we'll pick a crop and list the insects that attack it along with additional helpful information. The insect list is based on the information found in the Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management field guide. The field guide offers information describing lifecycle, damage description, monitoring/scouting strategies, economic thresholds (where available) and control options) for each economic pest.

 

In addition to an Insect of the Week, we'll also feature one of the entomologists that helps support the PPMN, either directly or indirectly.

Weekly Update (July 2, 2020; Wk 10) Otani, Weiss, Rounce, Trudel, Svendsen, Tansey, Turkington, Olfert, Vankosky

Happy Birthday Canada!

Warmer temperatures last week continue to move our growing season forward and there are more insects to prioritize on scouting lists again this week. Bertha armyworm pheromone monitoring numbers are coming in as cooperators work with their provincial networks to help assess risk levels in the form of cumulative moth counts.  We are also poised for wheat midge emergence across the prairies and we dedicate this Weekly Update and remember Dr. John Doane, an entomologist whose research on this pest and many other species contributed significantly to insect pest management on the Canadian prairies.

Access information to support your in-field insect monitoring efforts in the complete Weekly Update either as a series of Posts for Week 10 OR a downloadable PDF.

Stay Safe!

Questions or problems accessing the contents of this Weekly Update?  Please e-mail Meghan.Vankosky@canada.ca or Jennifer.Otani@canada.ca.  Past “Weekly Updates” can be accessed on our Weekly Update page.

John Frederick Doane (14 April 1930 – 21 May 2020)

In memory 

John Frederick Doane quietly passed away on May 21, 2020, in his home in Saskatoon, at the age of 90 years.  Having grown up on a farm north of Toronto, John developed an interest in entomology at a young age, and began collecting insect specimens common to southern Ontario.  John received his B.S.A. in 1954 from the Ontario Agricultural College, now the University of Guelph; specializing in entomology.  Pursuing these interests, John immediately enrolled in graduate studies at the University of Wisconsin, completing both his M.Sc. (1956) and his Ph.D. (1958).  Shortly after graduating, he began a research career in agricultural entomology, receiving an Research Scientist position at the Agriculture Canada Research Station in Saskatoon that same year.  Interestingly, this cadre of  Research Scientists at the Centre still had a significant number of first generation entomologists appointed to the Dominion Entomological Laboratory at Saskatoon.

John Frederick Doane (14 April 1930 - 21 May 2020)
Photo taken July 2019

John adapted very quickly to the agricultural industry on the prairies, and his research over the years has significantly contributed to insect population monitoring.  His first research assignment was to assess and describe the ecology and behaviour of wireworms, a major pest of field crops at the time.  John began by investigating the ovipositional behaviour and fecundity of adults, as well as the effects of soil moisture and temperature on wireworm egg survival.  His studies, related to the response of wireworm larvae to carbon dioxide levels, contributed to the development of trapping and monitoring tools for larval populations.  In the early 1980s, Saskatchewan experienced an unexpected outbreak of wheat midge (Sitodiplosis mosellana).  John was asked to assemble a multidisciplinary research team with the objectives to determine the biology and ecology of this new threat to wheat production in the prairies.  His research promptly yielded important contributions: (i) the discovery of a significant biological control insect (Macroglenes penetrans), and (ii) the development of a sound wheat midge population monitoring protocol.  Through the successful implementation of conservation techniques, M. penetrans now controls an average of >30% of the wheat midge across Saskatchewan annually.  A study in the 1990s, showed that the dollar value of the parasitoid to the agriculture industry over the 10 years, was in excess of $248.3 million (equivalent of $422.5 million today).  The second highlight, a soil extraction protocol for wheat midge larval cocoons, provided a unique population density and distribution monitoring tool for both the pest wheat midge and it’s biological control agent.  This tool is still utilized today to forecast the risk to wheat production; the survey results being provided as mapped forecasts for producers on an annual basis.  Given the success of biological control agent (M. penetrans), John collaborated with international colleagues at CABI in Switzerland, to assess the viability of importing a second biocontrol agent for control of wheat midge.  This resulted in the successful introduction and establishment of Platygaster tuberosula.  In the late 1980s, wheat production south of the USA border was seriously threatened by Russian wheat aphid (Diuraphis noxia).  In response to this new threat, John manufactured and installed a series of suction traps as an early-warning system, from southern to northern Saskatchewan.  The 30ft high traps were designed to collect migratory aphid adults being transported north on wind currents from infestations in the USA.  The results indicated that southwest SK was occasionally at low risk, but the threat was significantly less than south of the border.

John was appointed Head of the Integrated Pest Management Section of the Saskatoon Research Station in 1982, and the Head of the amalgamated Cereals Protection Section in 1989.  John served as E.S.S. President in 1967 and 1978, and served a term as a member of the E.S.C.  Governing Board.  He will also be remembered as a founding  member of the national AAFC Biological Control Working Group, a group that is still very active in 2020.  He retired in 1993, taking an extended self-guided tour of south east Asia, including India and Malaysia.  Upon his return, John remained active in retirement, co-authoring several scientific articles, most recently a bio-climate modelling paper on wheat midge in 2020.

- Submitted by O. Olfert

Weather synopsis

Weather synopsis – This week (June 22-28, 2020), prairie temperatures were warmest in Manitoba and eastern Saskatchewan (Table 1).  Seven-day cumulative temperatures varied across the prairies (Fig. 1).  Average 7-day temperatures continue to be warmest across Manitoba and eastern Saskatchewan and coolest across most of Alberta (Table 1). The weekly average temperature at Winnipeg (20.8 °C) was 6 °C warmer than Grande Prairie (Table 1; Fig. 1).  

Table 1. Seven-day temperature and rainfall summary (June 22-28, 2020).

Figure 1. Observed average temperatures across the Canadian prairies for the past seven days (June 22-28, 2020).

Average 30-day (May 30 - June 28, 2020) temperatures continue to be cooler in Alberta and areas north of Saskatoon than in southern Saskatchewan and Manitoba (Table 2, Fig. 2).  The average 30-day temperature at Winnipeg and Brandon continues to be greater than locations in Alberta and Saskatchewan (Table 2).  Based on growing season temperatures (April 1 – June 28, 2020), conditions were warmest for southern locations (Table 3). 

Table 2. 30-day temperature and rainfall summary (May 30 -June 28, 2020).

Figure 2. Observed average temperatures across the Canadian prairies for the past 30 days (May 30-June 28, 2020).

Table 3. Temperature and rainfall summary for the growing season (April 1 - June 28, 2020).

Cumulative rainfall for the past 7 days was variable (Table 1; Fig. 3). Lethbridge reported 23.3 mm and 7.7 mm was recorded at Swift Current (Table 1). Cumulative 30-day rainfall was greatest across central regions of Alberta (Table 2; Fig. 4).  Rainfall amounts were lower across the southern prairies (Fig. 4). Total 30-day rainfall at Winnipeg, Brandon, Regina and Swift Current has been less than 65 mm (Table 2; Fig. 4).  Rainfall amounts have been greater across central regions of Alberta and Saskatchewan (Fig. 4).  Saskatoon has reported 131.9 mm (279% of normal) in the past 30 days (Fig. 5).  Growing season rainfall (percent of average) is below normal southern Saskatchewan and most of Manitoba (Fig. 5; Table 3).  Rainfall amounts are above average across central regions of Saskatchewan and across Alberta (Fig. 5; Table 3).

Figure 3. Observed cumulative precipitation across the Canadian prairies for the past seven days (June 22-28, 2020).

Figure 4. Observed cumulative precipitation across the Canadian prairies for the past 30 days (May 30-June 28, 2020).

Figure 5. Percent of average precipitation for the growing season (April 1-June 28, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (28Jun2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The growing degree day map (GDD) (Base 5 ºC, April 1-June 30, 2020) is below (Fig. 6):

Figure 6. Growing degree day map (Base 5 °C) observed across the Canadian prairies for the growing season (April 1-June 30, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (02Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The growing degree day map (GDD) (Base 10 ºC, April 1-June 30, 2020) is below (Fig. 7):

Figure 7. Growing degree day map (Base 10 °C) observed across the Canadian prairies for the growing season (April 1-June 28, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (02Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The highest temperatures (°C) observed the past seven days ranged from <17 to >32 °C in the map below (Fig. 8).

Figure 8. Highest temperatures (°C) observed across the Canadian prairies the past seven days (April 1-June 28, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (02Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

Finally, the map below reflects how many days >25 °C have occurred so far across the prairies as of June 30, 2020 (Fig. 9). 

Figure 9. Number of days with temperatures above 25 °C)observed across the Canadian prairies this growing season  (April 1-June 30, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (02Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The maps above are all produced by Agriculture and Agri-Food Canada.  Growers can bookmark the AAFC Current Conditions Drought Watch Maps for the growing season.  Historical weather data can be access at the AAFC Drought Watch website, Environment Canada's Historical Data website, or your provincial weather network.

Predicted grasshopper development

Grasshopper Simulation Model Output – The grasshopper simulation model will be used to monitor grasshopper development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of grasshopper development stages based on biological parameters for Melanoplus sanguinipes (Migratory grasshopper). 

As of June 28, 2020, the grasshopper model estimates that hatch is nearly complete (Table 1).  The prairie average, is 77% (71% last week).  The majority of the nymphal population is predicted to be in the first to third instars (Table 1; Fig. 1).  This week, 5th instar nymphs are predicted to occur in some locations (Fig. 1).  Across the prairies, populations are predicted to be 21, 22, 21, 23, 11 and 2% in egg, first, second, third, fourth and 5th instar stages,  respectively (Table 1).  
 
Table 1. Results of grasshopper simulation (Melanoplus sanguinipes) development as of June 28, 2020.

Figure 1. Predicted average instar stages of grasshopper (Melanoplus sanguinipes) populations across
the Canadian prairies (as of June 28, 2020). 

Warmer conditions across southern regions of the prairies should result in rapid development of 1st to 3rd nymphs (Table 1).  This week 5th instar nymphs are predicted to appear at Regina, Brandon and Winnipeg (Table 1).  The two graphs compare development for Saskatoon (Fig. 2) and Winnipeg (Fig. 3).  Grasshopper populations near Saskatoon are predominantly in the 2nd and 3rd instars (Fig. 2) while populations near Winnipeg are expected to be primarily 3rd and 4th instars (Fig. 3).

Figure 2. Predicted grasshopper (Melanuplus sanguinipes) phenology at Saskatoon SK.
Values are based on model simulations (April 1-June 28, 2020).

Figure 3. Predicted grasshopper (Melanuplus sanguinipes) phenology at Winnipeg MB.
Values are based on model simulations (April 1-June 28, 2020).

Biological and monitoring information related to grasshoppers in field crops is posted by Manitoba Agriculture, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture and the Prairie Pest Monitoring Network.  Also refer to the grasshopper pages within the "Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide" (Philip et al. 2018) as an English-enhanced or French-enhanced version.

Bertha armyworm monitoring

Bertha armyworm (Lepidoptera: Mamestra configurata) - Model simulations for June 28, 2020, indicate that 26% of the population is in the pupal stage (compared to 69% last week), 52% in the adult stage (26% last week), and 20% are predicted to be eggs (5% last week).  Larvae are predicted to begin to occur (2%) this week. Across the Parkland and Peace River regions BAW populations are predicted to be transitioning from the pupal to adult stage (Fig. 1).  BAW adults should be showing up in traps.  Populations across southern regions are primarily in the egg stage (green region in Fig. 1).  Over the next 7-10 days larvae should begin to appear in this region.  

Development near Brandon (Fig. 2) is predicted to be ahead of fields near Saskatoon (Fig. 3).  First instar larvae are predicted to be occurring in southern Manitoba (Fig. 3). 

Figure 1. Predicted percent of bertha armyworm (Mamestra configurata) population at adult stage as of June 28, 2020. 

Figure 2. Predicted bertha armyworm (Mamestra configurata) phenology at Saskatoon SK as of June 28, 2020.

Figure 3. Predicted bertha armyworm (Mamestra configurata) phenology at Brandon MB as of June 28, 2020.

Figure 4. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D).
Photos: J. Williams (Agriculture and Agri-Food Canada)

Weekly Pheromone-baited Trapping Results - Early season detection of bertha armyworm is improved through the use of pheromone-baited unitraps traps deployed in fields across the Canadian prairies.  Click each province to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba as they become available. Check these sites to assess cumulative counts and relative risk in your geographic region.

Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting.  Use the images above (Fig. 4) to help identify egg masses and the economically important larvae in canola.  Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm! 

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.

Predicted wheat midge development

Wheat Midge (Sitodiplosis mosellana) – Wheat midge overwinter as larval cocoons in the soil.  Soil moisture conditions in May and June can have significant impact on wheat midge emergence.  Adequate rainfall promotes termination of diapause and movement of larval to the sol surface where pupation occurs.  Insufficient rainfall in May and June can result in delayed movement of larvae to the soil surface. Elliott et al. (2009) reported that wheat midge emergence was delayed or erratic  if rainfall did not exceed 20-30 mm during May.  Olfert et al. (2016) ran model simulations to demonstrate how rainfall impacts wheat midge population density. Our wheat midge model (Olfert et al. 2020) indicates that dry conditions may result in:
    a. Delayed adult emergence and oviposition 
    b. Reduced numbers of adults and eggs

As of June 28, 2020, midge model runs indicate that, where midge are present, pupation is occurring across Alberta, northwest Saskatchewan and southern Manitoba (Fig. 1).  Simulations suggest that the first adults might be emerging now (Fig. 2).  

Figure 1. Predicted  percent of population of wheat midge (Sitodiplosis mosellana) at pupal stage across
the Canadian prairies (as of June 28, 2020).

Figure 2. Predicted  percent of population of wheat midge (Sitodiplosis mosellana) at adult stage across
the Canadian prairies (as of June 28, 2020).

Females lay eggs on developing wheat heads.  This typically occurs in evenings when winds are calm. The wheat midge monitoring protocol suggests that wheat fields should be inspected for adults in late June and early July as wheat heads are emerging.  The next three weeks are very important for monitoring wheat midge populations for the purpose of making management decisions.  

Simulations were run to July 21 to assess population development over the next three weeks.  The first two graphs illustrate that adult wheat midge populations near Saskatoon (Fig. 3) and Lacombe (Fig. 4) are expected to emerge on June 30 and July 1, respectively.  

Figure 3. Predicted wheat midge (Sitodiplosis mosellana) phenology at Saskatoon SK projected to July 21, 2020.

Figure 4. Predicted wheat midge (Sitodiplosis mosellana) phenology at Lacombe AB projected to July 21, 2020.

Oviposition will occur soon after adult emergence.  Adult numbers are predicted to peak in mid July (Fig. 3 and 4).  A comparison of the synchrony between wheat midge and wheat is represented in Figure 5 and indicates that adult emergence and oviposition may occur when the crop is most susceptible near Saskatoon.  This information can be used as a guide to determine when fields should be monitored.

Figure 5. Comparison of predicted phenology of wheat midge (Sitodiplosis mosellana) and wheat at Saskatoon SK projected to July 21, 2020.

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

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 Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Diamondback moth

Diamondback moth (Plutellidae: Plutella xylostella) - Once diamondback moth is present in the area, it is important to monitor individual canola fields for larvae.  Warm growing conditions can quickly translate into multiple generations in a very short period!

Wind Trajectory Updates - Completed for 2020 growing season as of Week 09 (released June 22, 2020).

Weekly Pheromone-baited Trapping Results - Early season detection of diamondback moth is improved through the use of pheromone-baited delta traps deployed in fields across the Canadian prairies.  Click each province to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba as they become available. Check these sites to assess cumulative counts and relative risk in your geographic region.

Monitoring:
Remove the plants in an area measuring 0.1 m² (about 12" square), beat them on to a clean surface and count the number of larvae (Fig. 1) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.

Figure 1. Diamondback larva measuring ~8 mm long.
Note brown head capsule and forked appearance of prolegs on posterior.

Figure 2. Diamondback moth pupa within silken cocoon.

Economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant).  Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).

Figure 3. Diamondback moth.

Biological and monitoring information for DBM is posted by Manitoba Agriculture, Saskatchewan Agriculture, and the Prairie Pest Monitoring Network.  

More information about Diamondback moths can be found by accessing the pages from the  "Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide".  View ONLY the Diamondback moth page but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Pea leaf weevil

Pea Leaf Weevil (Sitona lineatus) –  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. Weevil larva in soil (Photo: L. Dosdall).

Figure 3. Pea nodules damaged by larval feeding (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.

Also refer to the pea leaf weevil page within the "Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide" - both English-enhanced or French-enhanced versions are available.