Weekly Update (June 18, 2020; Wk 08) Otani, Weiss, Rounce, Trudel, Svendsen, Evenden, Turkington, Olfert, Vankosky

Another BIG Weekly Update - several predictive model updates have been generated this week! Find updated information for bertha armyworm, grasshoppers, cereal leaf beetle, alfalfa weevil, wheat midge and pea leaf weevil.  Keep scrolling down and it's time to get in fields to scout!

Access information to support your in-field insect monitoring efforts in the complete Weekly Update either as a series of Posts for Week 8 OR a downloadable PDF.

Stay Safe!

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

Subscribe to the Blog by following these easy steps!

Weather synopsis

Weather synopsis – This week (June 8-14, 2020), temperatures were generally warmer than average and seven day rainfall totals were above average.  Average 7-day temperatures were warmest across Manitoba, Saskatchewan and eastern Alberta.  Temperatures were cooler across the Parkland and Peace River regions.  The weekly average temperature at Brandon (16.8 °C) was more than 3 °C warmer than at Grande Prairie.  

Table 1. 7-day temperature and rainfall summary (June 8-14, 2020)

Figure 1. Observed average temperatures across the Canadian prairies for the past seven days (June 8-14, 2020).

Average 30-day (May 16 - June 14, 2020) temperatures continue to be cooler in Alberta than in Saskatchewan and Manitoba.  Temperature anomalies indicated that northwestern Saskatchewan and a region extending from Calgary to Grande Prairie has been 0 to 2 °C cooler than normal. Most of Manitoba and Saskatchewan have been 0 to 2 °C warmer than normal (May 19 - Jun 15, 2020).  

Table 2. 30-day temperature and rainfall summary (May 16 -June 14, 2020)

Figure 2. Observed average temperatures across the Canadian prairies for the past seven days (May 16-June 14, 2020).

Figure 3. Mean temperature difference from Normal across the Canadian prairies the past 30 days (May 19-June 15, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (15Jun2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209  

This past week, rainfall amounts were greatest in Alberta and southern/east-central Saskatchewan. Rainfall in Manitoba was minimal.  Seven-day total rainfall for Grande Prairie was 35.4 mm compared to 1.7 mm at Brandon.  Eastern Saskatchewan and Manitoba have had the lowest 30-day cumulative rainfall amounts; precipitation has been greatest in Alberta.  At Saskatoon and Lacombe, rainfall has been greater than 200% of long term (30-day) normal values.  Conditions continue to be dryer than normal across most of Saskatchewan and Manitoba.  Rainfall amounts have been well above normal across most of Alberta as well as northwestern Saskatchewan. 

Figure 4. Observed cumulative precipitation across the Canadian prairies for the past seven days (June 8-14, 2020).

Figure 5. Observed cumulative precipitation across the Canadian prairies for the past 30 days (May 16-June 14, 2020).

Figure 6. Percent of average precipitation the past 30 days (May 16-June 14, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (15Jun2020). 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 15, 2020) is below (Fig. 7):

Figure 7. Growing degree day map (Base 5 °C) observed across the Canadian prairies for the growing season (April 1-June 15, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (15Jun2020). 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 1, 2020) is below (Fig. 8):

Figure 8. Growing degree day map (Base 10 °C) observed across the Canadian prairies for the growing season (April 1-June 15, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (15Jun2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The lowest temperatures (°C) observed the past seven days ranged from <-1 to >8 °C in the map below (Fig. 9).

Figure 9. Lowest temperatures (°C) observed across the Canadian prairies the past seven days (April 1-June 15, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (15Jun2020). 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 <15 to >32 °C in the map below (Fig. 10).

Figure 10. Highest temperatures (°C) observed across the Canadian prairies the past seven days (April 1-June 15, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (15Jun2020). 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.

Wind Trajectories

Agriculture and Agri-Food Canada (AAFC) and Environment and Climate Change Canada (ECCC) have been working together to study the potential of trajectories for monitoring insect movements since the late 1990s.

The entire list of 2020 Wind Trajectory Reports is available here.
→ Read the WEEKLY Wind Trajectory Report for Wk08 (released June 15, 2020).

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 14, 2020, the simulation estimates that hatch varies between 14.5% at Grande Prairie and Lacombe to more than 85% at Winnipeg and Regina (Table 1; Fig. 1).  The prairie average, is 34% (20% last week) and well above the long term average of 10% (4.5% last week) for this point in the growing season (Fig. 1).  Across the prairies, populations are predicted to be 65, 18, 11 and 4% in egg, first, second, and third instars, respectively (Table 1).  

Table 1.  Predictive model output estimates for Melanoplus sanguinipes development (% of total population for each location) at selected sites across the Canadian prairie as of June 14, 2020.

Figure 1. Grasshopper hatch (%) based on model simulations using current environmental conditions (blue bars) compared to long-term normal (red bars) as of June 14, 2020.
*LTN = long term climate normals, used for comparison of current year development (OBS)

Grasshopper hatch is greatest in across the southern prairies; areas bound within the black line in the map below are those where 50% or more of eggs have hatched, according to the simulation model (Fig. 2).  

Figure 2. Predicted percent of grasshopper (Melanoplus sanguinipes) population at hatching stage across
the Canadian prairies (as of June 14, 2020). 

First instar grasshoppers are predicted to be present across the prairies, with first occurrence of hatchlings near Edmonton and southern Peace River region in the past week (Fig. 3).  Warmer conditions across southern regions of the prairies should result in appearance of third instar nymphs (Fig. 4).  

Figure 3. Predicted percent of grasshopper (Melanoplus sanguinipes) population at first instar stage across
the Canadian prairies (as of June 14, 2020). 

Figure 4. Predicted percent of grasshopper (Melanoplus sanguinipes) population at third instar stage across
the Canadian prairies (as of June 14, 2020). 

The two graphs compare development for Regina and Saskatoon.  The graphs illustrate that grasshopper populations near Saskatoon are predominantly in the first instar with relatively few grasshoppers in the second and third instars (Fig. 5).  Populations near Regina may be expected to have grasshoppers nymphs in first to fourth instar stages of development (Fig. 6).

Figure 5. Predicted grasshopper (Melanuplus sanguinipes) phenology at Saskatoon SK.
Values are based on model simulations (April 1-June 14, 2020).

Figure 6. Predicted grasshopper (Melanuplus sanguinipes) phenology at Regina SK.
Values are based on model simulations (April 1-June 14, 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 to June 14, 2020, indicate that pupal development is greater than 90% across most of Saskatchewan and Manitoba.  Pupal development is predicted to be slower across central and northern regions of Alberta.  First occurrence of BAW should be occurring in isolated regions across southern Alberta, Saskatchewan and Manitoba. In fact, adult BAW were reported in Saskatoon by Dr. Julie Soroka on June 17, 2020.  By next week adults should be emerging across most of the prairies.  

Figure 1. Predicted bertha armyworm (Mamestra configurata) pupal development across
the Canadian prairies as of June 14, 2020. 

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.

Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting.  Use the images below (Fig. 2) 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!

Figure 2. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D).
Photos: J. Williams (Agriculture and Agri-Food Canada)

Cereal leaf beetle

Cereal leaf beetle (Oulema melanopus) - As of June 14, 2020, cereal leaf beetle (CLB) simulations indicate that oviposition is almost complete with 30% of the population in the egg stage (Table 1).  

Table 1. Predictive model output estimates for O. melanopus development (% of total population for each location) at selected sites across the Canadian prairies (as of June 14, 2020).

Across the prairies, first instar larvae are predicted to be most abundant (prairie average; Fig. 1).  This week, fourth instar larvae may begin to occur.  The following three maps illustrate larval development of first (Fig. 1), second (Fig. 2) and third instar (Fig. 3) stages across the prairies. Based on the simulation, development is greatest across southern Manitoba and southern Saskatchewan.

Figure 2. Predicted percent of cereal leaf beetle (Oulema melanopus) population at first instar stage across the Canadian prairies (as of June 14, 2020).  

Figure 3. Predicted percent of cereal leaf beetle (Oulema melanopus) population at second instar stage across the Canadian prairies (as of June 14, 2020).  

Figure 4. Predicted percent of cereal leaf beetle (Oulema melanopus) population at third instar stage across the Canadian prairies (as of June 14, 2020).  

Manitobans - Dr. John Gavloski is looking for samples of cereal leaf beetle larvae this growing season to determine their range across Manitoba, their population density, and the rate at which larvae are parasitized. Please contact John.Gavloski@gov.mb.ca or @JohnTheBugGuy if you observe cereal leaf beetles in your fields. 

Canadians - Dr. Haley Catton is looking for samples of cereal leaf beetle larvae this growing season too!  Help her monitor for the tiny beneficial wasp, Tetrastichus julis, that lives inside the larvae of cereal leaf beetle.  Tracking these biological control agents will help Dr. Catton learn more about their distribution and value in fields.  Please check her Twitter poster for more details or contact her at @HaleyCatton or Haley.Catton@canada.ca . Access the recently released Pests & Predators podcast by Real Agriculture which features Dr. Haley Catton and this powerful parasitoid!

Lifecycle and Damage:

Adult: Adult cereal leaf beetles (CLB) have shiny bluish-black wing-covers (Fig. 3). The thorax and legs are light orange-brown. Females (4.9 to 5.5 mm) are slightly larger than the males (4.4 to 5 mm). Adult beetles overwinter in and along the margins of grain fields in protected places such as in straw stubble, under crop and leaf litter, and in the crevices of tree bark. They favour sites adjacent to shelter belts, deciduous and conifer forests. They emerge in the spring once temperature reaches 10-15 ºC and are active for about 6 weeks. They usually begin feeding on grasses, then move into winter cereals and later into spring cereals.  

Figure 3. Adult Oulema melanopus measure 4.4-5.5 mm long (Photo: M. Dolinski).

Egg: Eggs are laid approximately 14 days following the emergence of the adults. Eggs are laid singly or in pairs along the mid vein on the upper side of the leaf and are cylindrical, measuring 0.9 mm by 0.4 mm, and yellowish in colour. Eggs darken to black just before hatching.  

Larva: The larvae hatch in about 5 days and feed for about 3 weeks, passing through 4 growth stages (instars). The head and legs are brownish-black; the body is yellowish. Larvae are usually covered with a secretion of mucus and fecal material, giving them a shiny black, wet appearance (Fig. 4).  When the larva completes its growth, it drops to the ground and pupates in the soil. 

Figure 4.  Larval stage of Oulema melanopus with characteristic feeding 
damage visible on leaf (Photo: M. Dolinski).

Pupa: Pupal colour varies from a bright yellow when it is first formed, to the colour of the adult just before emergence. The pupal stage lasts 2 - 3 weeks. Adult beetles emerge and feed for a couple of weeks before seeking overwintering sites. There is one generation per year.

Fact sheets for CLB are published by the province of Alberta and available from the Prairie Pest Monitoring Network. Also access the Oulema melanopus page from the "Field crop and forage pests and their natural enemies in western Canada - Identification and management field guide" available as a free downloadable document in either an English-enhanced or French-enhanced version.

Alfalfa weevil

Alfalfa Weevil (Hypera postica) – Model output indicates that hatch is almost complete with less than 5% of the population predicted to still be in the egg stage (prairie average; Table 1). Across the prairies, populations are predicted to be 12, 45, 29 and 10% in first, second, third and fourth instars, respectively.  

Table 1.  Predictive model output estimates for Hypera postica development (% of total population for each location) at selected sites across the Canadian prairie as of June 14, 2020.

Larval populations in the Peace River region are expected to be mostly in the second instar (Fig. 1).  Last week, the presence of third instar larvae was limited to areas southeast of Saskatchewan and extended into Manitoba (Fig. 2).  This week third instar larvae should be occurring across southern and central regions of the prairies (Fig. 3).  Fourth instar larvae should be abundant across southern Manitoba and southeastern Saskatchewan.

Figure 1. Predicted percent of populations of alfalfa weevil (Hypera postica) in the second instar stage across

the Canadian prairies as of June 14, 2020. 

Figure 2. Predicted percent of populations of alfalfa weevil (Hypera postica) in the third instar stage across

the Canadian prairies as of June 14, 2020. 

Figure 3. Predicted percent of populations of alfalfa weevil (Hypera postica) in the fourth instar stage across

the Canadian prairies as of June 14, 2020. 

Monitoring

The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer” (Fig. 3, lower left).  The green larva featuring a dorsal, white line down the length of its body has a dark brown head capsule and will grow to 9 mm long (Fig. 3, upper right).  

Figure 3.  Developmental stages of the alfalfa weevil (Hypera postica); overwintered adult (upper row L-R), eggs, larvae, larva feeding or "skeletonizing" alfalfa leaf (lower row L-R), pupa within lacey cocoon, pupa, and newly emerged adult.

Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon).  Additional information can be accessed by reviewing the Alfalfa Weevil Page extracted from the "Field crop and forage pests and their natural enemies in western Canada - Identification and management field guide" (Philip et al. 2018). The guide is available as an English-enhanced or French-enhanced version.

Predicted pea leaf weevil development

Pea Leaf Weevil (Sitona lineatus) –  As of June 14, 2020, PLW model runs indicate that PLW females continue to oviposit eggs.  The following two graphs illustrate that egg numbers continue to increase at Swift Current (Fig. 1) and Lacombe (Fig. 2).  This week, first appearance of PLW larvae is expected to occur at Swift Current (Fig. 1). 

Figure 1. Predicted pea leaf weevil (Sitona lineatus) phenology at Swift Current SK.
Values are based on model simulations (April 1-June 14 2020).

Figure 2. Predicted pea leaf weevil (Sitona lineatus) phenology at Lacombe AB.
Values are based on model simulations (April 1-June 14 2020).

Link here to access photos of PLW and related species of weevils which can all be active simultaneously in Canadian prairie field crops. 

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. 

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 14, 2020, wheat midge model runs indicate that recent rainfall in Alberta and the Parkland region of Saskatchewan has resulted in movement of more than 80% of the larval population to the soil surface. Dryer conditions in other parts of Saskatchewan and in Manitoba continue to delay movement of larvae to the soil surface.  If dry conditions persist, this may result in delayed pupation and adult emergence.  

Figure 1. Predicted  percent of larval population of wheat midge (Sitodiplosis mosellana) at soil surface across
the Canadian prairies (as of June 14, 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 - Wind trajectory models used to deliver an early-warning system for the origin and destination of migratory invasive species indicated arrival events of air currents potentially carrying migrating diamondback moths from more southerly regions.  Access the Weekly Wind Trajectory Report (released June 15, 2020) to review where wind trajectories originating over Mexico, California, Texas or the Pacific Northwest cross locations in Manitoba, Saskatchewan, and Alberta.

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.

Field Heroes

The Field Heroes campaign continues to raise awareness of the role of beneficial insects in western Canadian crops. Check the recently updated Field Heroes website for scouting guides, downloadable posters, and videos. Learn about these important organisms at work in your fields!  

Real Agriculture went live with a weekly Pest and Predators podcast series!
• Access Episode 1 - Do you know your field heroes?
• Access Episode 2 - An inside look at the Prairie Pest Monitoring Network.
• Access Episode 3 - How much can one wasp save you?

Access ALL the Field Heroes links here and be sure to follow @FieldHeroes!