Insect of the Week – Pterostichus melanarius

Jennifer Otani
Week 6

This week’s insect is the ground beetlePterostichus melanarius (Coleoptera: Carabidae).  This large (12-19 mm), shiny black beetle originates from Europe and probably arrived to North America in the 1920s in ships’ ballasts. It has become a widespread insect throughout North America, particularly in habitats used by humans: urban areas, forests, and agricultural land.

Flight has been the main method of colonization and dispersal for this species. In newly arrived populations of P. melanarius, individuals generally have longer hind wings which allow for more efficient dispersal. After a population has become established in an area, short-winged morphs of the species become dominant.

This species is an excellent example of a generalist predator. Generalist predators include many species of ground beetles, some rove beetles, ants, centipedes and spiders. These arthropods are not picky when it comes to choosing a meal. For example, P. melanarius will eat nearly anything including many different arthropods, earthworms, slugs and even some small vertebrates. Generalist predators are effective in keeping some insects from reaching high numbers that can damage agricultural crops.

Find out more about ground beetles and Pterostichus melanarius at the Insect of the Week page!

Pterostichus melanarius
Photo credit: Henri Goulet (retired), Agriculture and Agri-Food Canada
Photograph of Pterostichus melanarius catching a fourth-instar P. xylostella in a plastic container (LRC, Photo credit: A. Mauduit)

Weekly Update

Jennifer Otani, Ross Weiss, David Giffen, Shelby Dufton, Hector Carcamo, Wim van Herk, Robert Vernon, Aimee McGowan, Meghan Vankosky, Erl Svendsen and Owen Olfert
Week 6


Access the complete Weekly Update either as a series of Posts for Week 06 (June 14, 2018) OR a downloadable PDF version.  Also review the “Insect of the Week” for Week 6!

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

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Weather synopsis

Ross Weiss, David Giffen, Owen Olfert and prairiepest_admin
Week 6

Weather synopsis – This past week (June 4  – 11, 2018), the average temperature (13.3 °C) was very similar to long term average (Fig. 1).  The warmest weekly temperatures occurred across MB. The 30-day (May 12 – June 11) average temperature (12.9 °C) was approximately 2 °C warmer than long term average (Fig. 2).  

Figure 1.  Weekly (June 4 – 11, 2018) average temperature (°C) . 
Figure 2.  The 30-day (May 12 – June 11, 2018) average temperature (°C).

Weekly and 30-day total precipitation was above average. The wettest region was across eastern areas in SK (Figs. 3 and 4). 

Figure 3.  Weekly (June 4 – 11, 2018) cumulative precipitation (mm).
Figure 4.  The 30-day (May 12 – June 11, 2018) cumulative precipitation (mm).

Accumulated precipitation for the growing season (April 01-June 11, 2018) is shown below.

The map below reflects the Highest Temperatures occurring over the past 7 days (June 5-11, 2018) across the prairies. 

The map below reflects the Lowest Temperatures occurring over the past 7 days (June 5-11, 2018) across the prairies. 

The growing degree day map (GDD) (Base 10ºC, March 1 – June 10, 2018) is below:

The growing degree day map (GDD) (Base 5ºC, March 1 – June 10, 2018) is below:

The maps above are all produced by Agriculture and Agri-Food Canada.  Growers may wish to bookmark the AAFC Drought Watch Maps for the growing season.


Wind trajectories

Ross Weiss, Serge Trudel and prairiepest_admin
Week 6

Background:  Agriculture and Agri-Food Canada (AAFC) and Environment and Climate Change Canada (ECCC) have been working together to study the potential of trajectories to deliver an early-warning system for the origin and destination of migratory invasive agricultural pests.

We receive two types of model output from ECCC: reverse trajectories (RT) and forward trajectories (FT): 

(i) ‘Reverse trajectories’ (RT) refer to air currents that are tracked back in time from specified Canadian locations over a five-day period prior to their arrival date. 

(ii) ‘Forward trajectories’ (FT) have a similar purpose; however, the modelling process begins at sites in USA and Mexico. The model output predicts the pathway of a trajectory. Again, of interest are the winds that eventually end up passing over the Prairies. 

Current Data

Since April 1. 2018, the majority of Pacific Northwest (PNW) air currents have crossed over southern AB (Fig. 1). The cumulative number of wind dispersal events for June 1 – 11, 2018 (181) is greater than the long term (2007 – 2017) average (98).

Figure 1.  Total reverse trajectories (originating from US – PNW) April 1 – June 11, 2018.

Since April 1, the majority of air currents from southwest USA and Mexico have crossed over eastern SK and western MB (Fig. 2). So far there have been 18 RT’s (June 1 – 11, 2018) and compares with 2017 (3) and the long term average (24). 

Figure 2.  Total number of reverse trajectories (originating from southern USA) April 1 – June 11, 2018.

Weather forecasts (7 day):


Wireworm distribution map

Wim van Herk, Robert Vernon, Aimee McGowan and prairiepest_admin
Week 6

Reminder – Last week turned out to be our wireworm blitz!  This complicated group of insect species was featured in the Insect of the Week AND we include the survey results again this week!

The following maps summarize the main results of a survey of pest species of wireworms of the Canadian Prairie Provinces.  Samples (both larvae and beetles) were submitted to Dr. Bob Vernon’s lab in Agassiz, BC, from 2004 to 2017, and identified by Dr. Wim van Herk (Fig. 1).  Species identifications were confirmed with barcoding.

Figure 1.  Sampling locations for click beetles and wireworm larvae (Coleoptera: Elateridae) submitted for wireworm surveying from 2004-2017.

Approximately 600 samples were submitted, with the number of larvae per sample typically less than five (Fig. 1).  More samples are welcome, particularly from areas currently not well represented on the maps.  Please provide either the legal land description or latitude and longitude coordinates with a sample.  Any information on the cropping history or whether fields were irrigated is helpful.

Review the complete survey summary posted in Week 05 (for Jun 7, 2018).

Please do not distribute or use the contents of this post, including any maps, without obtaining prior permission.

Obtain further information or arrange shipment of wireworm or click beetle samples by contacting:
Dr. Wim van Herk
Agriculture and Agri-Food Canada
Agassiz Research and Development Centre
6947 Highway 7, Agassiz, BC, V0M 1A0


Predicted grasshopper development

Ross Weiss, Owen Olfert and Meghan Vankosky
Week 6

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 11, 2018, predicted hatch was 74% (long term average was 28%). The average development is almost at second instar (Fig. 1) with 30, 28, 12 and 2% in the  first, second, third and fourth instar stages, respectively.  

Figure 1.  Grasshopper development (average instar) on model simulations, for April 1 – June 11, 2018.

Model output for Saskatoon illustrates that populations are primarily in the first and second instars with third and fourth instar stages beginning to appear (Fig. 2). This agrees with last week’s survey conducted south of Saskatoon SK. 

Figure 2.  Predicted grasshopper phenology at Saskatoon SK.
Values are based on model simulations, for April 1 – June 11, 2018.

Biological and monitoring information related to grasshoppers in field crops is posted by Manitoba AgricultureSaskatchewan AgricultureAlberta Agriculture and Forestry, the BC Ministry of Agriculture and the Prairie Pest Monitoring Network.  Also refer to the grasshopper pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” as an English-enhanced or French-enhanced version.


Predicted bertha armyworm development

David Giffen and prairiepest_admin
Week 6

Bertha armyworm (Lepidoptera: Mamestra configurata– BAW development continues to be 7-10 days ahead of normal development (Fig. 1).  

Figure 1.  Percentage of pupal stage heat requirements for emergence of bertha armyworm (as of June 20, 2018).

Near Saskatoon SK, adult emergence is well underway and oviposition is predicted to have begun this week. Based on climate data, oviposition near Saskatoon should begin around the third week of June.  

Reminder –Table 1. Projected dates for BAW adult emergence for June 4, 2018 (projected to June 30, 2018).

For those who are  now checking a bertha armyworm pheromone trap on a weekly basis, we provide an excellent photo kindly shared by Saskatchewan Agriculture to aid your identification and reporting of trap interceptions.  Note the kidney-bean white-patterned shape on each forewing but also know other cutworm species can resemble bertha armyworm moths so check carefully and thanks for your help!

Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of ManitobaSaskatchewanAlberta and the Prairie Pest Monitoring Network.  Also refer to the bertha armyworm pages within the new “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.


Wheat midge

Ross Weiss, Owen Olfert and Meghan Vankosky
Week 6

Wheat Midge (Sitodiplosis mosellana– Simulation modelling is used to predict wheat midge emergence across the Canadian prairies.  The wheat midge model indicates that wheat midge larvae should be moving to the soil surface (Fig. 1). Adequate moisture has resulted in expected emergence patterns. 

Figure 1.  Predicted wheat midge phenology at Saskatoon SK.
Values are based on model simulations, for April 1 – June 11, 2018 (projected to July 15, 2018). 

The 2018 wheat midge forecast map was circulated in January and is posted below for reference.  Note that areas highlighted orange or red in the map below included surveyed fields with comparatively higher densities of wheat midge cocoons last fall.

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.  Additionally, more information 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.


Pea leaf weevil

Owen Olfert, Ross Weiss and Meghan Vankosky
Week 6

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.

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.  A review of this insect was published in 2011 in Prairie Soils and Crops by Carcamo and Vankosky.


Alfalfa weevil

Ross Weiss, Owen Olfert and prairiepest_admin
Week 6

Alfalfa Weevil (Hypera postica) – Approximately 70% of the population should be in the third or fourth instar stages and pupae may be occurring as well.  AAW populations near Winnipeg, Brandon, Regina, Saskatoon and regions in southern Alberta are predicted to be primarily in the fourth instar (Fig. 1). 

Figure 1.  Average predicted development stages of alfalfa weevil. 
Values are based on model simulations (April 1-June 11, 2018). 

Access last week’s update to view photos and descriptions of all stages of alfalfa weevil.  

Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon).  Additional information can be accessed by reviewing the Alfalfa Weevil Page extracted from the “Field crop and forage pests and their natural enemies in western Canada – Identification and management field guide” (Philip et al. 2015).  The guide is available in both a free English-enhanced or French-enhanced version.


Lygus in canola

Ross Weiss, Owen Olfert and Meghan Vankosky
Week 6

Lygus bugs (Lygus spp.) – Lygus development is well underway. Adults have moved in to the fields and oviposition should be almost complete. The Lygus model suggests that populations near Brandon MB should consist of first to third instar stages (Fig. 1). 

Figure 1.  Predicted Lygus phenology at Brandon MB.
Values are based on model simulations, for April 1 – June 11, 2018.

On average, prairie populations are predicted to be in the first or second instar stages with development being greatest across the southern prairies (Fig. 2). 

Figure 2.  Predicted average developmental Lygus stage.
Values are based on model simulations, for April 1 – June 11, 2018.

Remember – The economic threshold for Lygus in canola is applied at late flower and early pod stages.  

Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo:  AAFC-Saskatoon).

Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.

Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.

Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.

Sequential sampling for lygus bugs at late flowering stage in canola.

The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.

Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop. 

Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production.  The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage.  In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.

Table 1.  Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).

1 Canola crop stage estimated using Harper and Berkenkamp 1975).
2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).

Table 2.  Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).

 3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).

Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol.  Also refer to the Lygus pages within the new “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.


Cabbage seedpod weevil

Jennifer Otani
Week 6

Cabbage seedpod weevil (Ceutorhynchus obstrictus) –  There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo).  Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.


  • Begin sampling when the crop first enters the bud stage and continue through the flowering. 
  • Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.  
  • Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.  
  • Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.  
  • An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts). 
  • Consider making insecticide applications late in the day to reduce the impact on pollinators.  Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.  
  • High numbers of adults in the fall may indicate the potential for economic infestations the following spring.

Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss.  Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo).  Eggs are oval and an opaque white, each measuring ~1mm long.  Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.

There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo).  The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds.  A single larva consumes about 5 canola seeds.  The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell.  Approximately 10 days later, the new adult emerges to feed on maturing canola pods.  Later in the season these new adults migrate to overwintering sites beyond the field.

Please find additional detailed information for CSPW in fact sheets posted by Alberta Agriculture and ForestrySaskatchewan Agriculture, or the Prairie Pest Monitoring Network.


Provincial Insect Pest Reports

James Tansey, John Gavloski and Scott Meers
Week 6

Provincial entomologists provide insect pest updates throughout the growing season so we link to their most recent information: 

Manitoba‘s Insect and Disease Update for 2018 will be posted soon. Review the most recent update (June 6, 2018) prepared by John Gavloski and Holly Derksen. The insect update notes flea beetles in canola and cutworms with monitoring for alfalfa weevil larvae underway. Diamondback moth trap numbers remain low and bertha armyworm pheromone traps will go up this week.

Saskatchewan‘s Crop Production News for 2018 is now posted. Access Report #2 posted June 7, 2018. Insect monitoring information is included in the article, “Troubleshooting emergence and assessing plant stand densities in flax or canola“. Saskatchewan growers can review articles posted for flea beetles, pea leaf weevils. Also note the following updated diamondback moth pheromone trap interception counts from across the regions (updated June 15, 2018):

Alberta Agriculture and Forestry’s Call of the Land regularly includes insect pest updates from Scott Meers. The most recent Call of the Land (posted on June 7, 2018) and identified concerns with stem feeding by flea beetles with the cooler weather this past week, reports of dung beetle larvae in some irrigated fields, continuation of pea leaf weevil surveying into central Alberta, and transient presence of some blister beetles. Updated June 14, 2018.


Monarch migration

Jennifer Otani
Week 6

We continue to track the migration of the Monarch butterflies as they move north by checking the 2018 Monarch Migration Map!  A screen shot of the map has been placed below as an example (retrieved 12Jun2018) but follow the hyperlink to check the interactive map.  Last week monarchs were spotted in Manitoba and this week they’ve entered Saskatchewan!

Visit the Journey North website to learn more about migration events in North America and visit their monarch butterfly website for more information related to this fascinating insect.