Weekly Update

Jennifer Otani, Ross Weiss, David Giffen, Serge Trudel, Sandra Younie, Erl Svendsen, Owen Olfert and Meghan Vankosky
Categories
Week 17

Greetings!

Week 17 and field scouting continues to be critical!

Please access the complete Weekly Update either as a series of Posts for Week 17 (August 1, 2019) OR a downloadable PDF. Be sure to check out the Insect of the Week – the rest of the growing season features doppelgangers to aid in-field scouting!

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.

Subscribe to the Blog by following these easy steps!

Weather synopsis

Ross Weiss, David Giffen, Serge Trudel, Owen Olfert and Meghan Vankosky
Categories
Week 17

This past week (July 22-28, 2019) temperatures were approximately 2 °C warmer than last week (Fig. 1). The warmest temperatures were observed in MB and southern AB while temperatures were cooler in western AB and the Peace River region. 

Figure 1. Average temperature (°C) across the Canadian prairies the past seven days (July 22-28, 2019).

Across the prairies, 30-day (June 28 – July 28, 2019) average temperatures have been approximately 1 °C cooler than normal (Fig. 2). Temperatures were warmest across MB and eastern SK. 

Figure 2. Average temperature (°C) across the Canadian prairies the past 30 days (June 28-July 28, 2019).

Growing season temperatures (April 1-July 28, 2019; Fig. 3) in AB and SK have been 1 °C cooler than average while central and eastern MB has been approximately 1 °C warmer than average (Fig. 4). 

Figure 3. Average temperature (°C) across the Canadian prairies for the growing season (April 1-July 28, 2019).
Figure 4. Mean temperature difference (°C) from Normal observed across the Canadian prairies for the growing season (April 1-July 31, 2019).  
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (01Aug2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

This past week significant rainfall amounts were reported the parkland region of  SK and AB (Fig. 5). Across the prairies, rainfall amounts for the past 30 days have been highly variable (Fig. 6). 

Figure 5. Cumulative precipitation observed the past seven days across the Canadian prairies (July 22-28, 2019).
Figure 6. Cumulative precipitation observed the past 30 days across the Canadian prairies (June 28-July 28, 2019).

Dryer conditions continue across southern AB and western SK. Growing season (April 1 – July 21, 2019; Fig. 7) rainfall amounts have been below average across southern regions of AB, and across MB (Fig. 8). 

Figure 7. Cumulative precipitation observed for the growing season (April 1-July 28, 2019) across the Canadian prairies.
Figure 8. Percent of average precipitation observed across the Canadian prairies for the growing season (April 1-July 31, 2019).  
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (01Aug2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

The growing degree day map (GDD) (Base 5 ºC, April 1-July 21, 2019) is below (Fig. 9):

The growing degree day map (GDD) (Base 10 ºC, April 1-July 21, 2019) is below (Fig. 10):

The lowest temperatures (°C) observed the past seven days ranged from at least 12 down to at least 0 °C in the map below (Fig. 11).

Figure 11.  Lowest temperatures (°C) observed across the Canadian prairies the past seven days (to July 31, 2019).  
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (01Aug2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

The highest temperatures (°C) observed the past seven days ranged from at least 18 up to at least 32 °C in the map below (Fig. 12).

Figure 12. Highest temperatures (°C) observed across the Canadian prairies the past seven days (to July 31, 2019).  
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (01Aug2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

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

Predicted grasshopper development

Ross Weiss, David Giffen, Serge Trudel, Owen Olfert and Meghan Vankosky
Categories
Week 17

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).

Based on model runs, approximately 24% of the population should be in the adult stage. Based on climate data, 32% of the population would be expected to be in adult stage. The first map indicates the average instar for grasshopper populations across the prairies (Fig. 1). The second map indicates adult populations are developing across southern MB and SK and a localized area in southern AB (Fig. 2).

Figure 1. Predicted development stages of grasshopper (Melanoplus sanguinipes) populations across the Canadian prairies (as of July 28, 2019). 
Figure 2. Predicted percent of grasshopper (Melanoplus sanguinipes) populations attaining adult stage across the Canadian prairies (as of July 31, 2019). 

The Insect of the Week’s Doppelganger featured GRASSHOPPERS for Week 14!!  Check out the excellent nymph photos to help your in-field scouting!

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 “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is available as a free downloadable document in either an English-enhanced or French-enhanced version.

Wheat midge

David Giffen, Owen Olfert and Meghan Vankosky
Categories
Week 17

Wheat Midge (Sitodiplosis mosellana) – Reminder – Based on fall surveys in 2018, wheat midge populations were expected to be low across most of AB and SK this season.  Dry conditions in May and June have resulted in reduced emergence of adult populations across most of SK. 

Review last week’s predictive model update (Wk 16) regarding the development for this pest.  This week, the percent of adult emergence is depicted across the Canadian prairies as of July 28, 2019 (Fig. 1). The map below predicts the geographic distribution and corresponding accumulation of heat units necessary for wheat midge to emerge from puparia developing in the soil.  Midge emergence is 100% complete in areas highlighted red, 90% complete in areas highlighted orange, and ≤50% in areas highlighted light orange or yellow (Fig. 1).

Figure 1.  Accumulation of heat units necessary for wheat midge  (Sitodiplosis mosellana) to emerge from puparia in the soil and corresponding estimated percent of midge emerged across the Canadian prairies as of July 28, 2019.

Monitoring:
When monitoring wheat fields, pay attention to the synchrony between flying midge and anthesis.

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (photographed by AAFC-Beav-S. Dufton & A. Jorgensen below). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.

REMEMBER that in-field counts of wheat midge per head remain the basis of economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (photographed by AAFC-Beav-S. Dufton below), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember your insecticide control options for wheat midge also kill these beneficial insects which help reduce midge populations.

Economic Thresholds for Wheat Midge:
a) To maintain optimum grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.
b) For yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.

Inspect the developing kernels for the presence of larvae and the larval damage. 

Wheat midge and its doppelganger, the lauxanid fly, were featured as the Insect of the Week (for Wk10).  Check that post for help with in-field scouting for this economic pest of wheat!  The differences between midges and parasitoid wasps are featured as the current Insect of the Week (for Wk11).  Not all flying insects are mosquitoes nor are they pests – many are important parasitoid wasps that actually regulate insect pest species in our field crops.

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.

Bertha armyworm monitoring

Jennifer Otani
Categories
Week 17

Bertha armyworm (Lepidoptera: Mamestra configurata– Predictive model updates are completed for the growing season but can be reviewed here (Wk 14).  

Important – Watch for updates from your provincial monitoring networks who are compiling cumulative pheromone-baited trap interceptions to assess risk levels in AlbertaSaskatchewan (updated 24Jul2019), and Manitoba (locate table on pg 6).  regions in all three prairie provinces are reporting “uncertain” risk based on pheromone-baited unitrap cumulative counts.  

This week – SCOUT NOW to confirm in-field larval counts and REMEMBER that LARVAL DENSITIES CAN VARY DRAMATICALLY even between adjacent fields!  Scout to protect @FieldHeroes and avoid economic losses! Use the Field Heroes’ scouting guide for bertha armyworm and be sure to read more at their website!

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 “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. 1) to help identify egg masses and the economically important larvae in canola.

Figure 1. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D).
Photos: J. Williams (Agriculture and Agri-Food Canada).

Now is the time to do in-field scouting for this insect pest.  Review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!

Lygus in canola

Jennifer Otani
Categories
Week 17

Lygus bugs (Lygus spp.) – The Insect of the Week’s doppelganger for Wk 15 was lygus bug versus the alfalfa plant bug while Wk 16 featured lygus bug nymphs vs. aphids!  Both posts include tips to to discern the difference between when doing in-field scouting!

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.

Scouting tips to keep in mind: 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.

Sampling becomes more representative IF repeated at multiple spots within a field.  For lygus bug monitoring, sampling is most accurate when repeated at a total of 15 spots within the field.  Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C). 

If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.

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 or French versions are available.

Scouting Charts – Canola and Flax

Jennifer Otani
Categories
Week 17

Reminder – One last time for this growing season….. We have updated the field scouting charts so they now link to pages within the 2018 version of the Insect Field Guide

We offer TWO generalized insect pest scouting charts to aid in-field scouting on the Canadian prairies:

1. CANOLA INSECT SCOUTING CHART

2018_ScoutingChart_Canola

2. FLAX INSECT SCOUTING CHART

2018_ScoutingChart_Flax

These charts feature hyperlinks directing growers to downloadable PDF pages within the “Field crop and forage pests and their natural enemies in western Canada: Identification and management field guide“.

Whenever possible, monitor and compare pest densities to established economic or action thresholds to protect and preserve pollinators and beneficial arthropods. Economic thresholds, by definition, help growers avoid crop losses related to insect pest species but they rely on in-field scouting!

West Nile Virus and Culex tarsalis

David Giffen, Owen Olfert and Meghan Vankosky
Categories
Week 17

West Nile Virus Risk –  Health Canada posts information related to West Nile Virus in Canada.  Health Canada also tracks West Nile Virus through humanmosquitobird and horse surveillance.  Link here to access the most current weekly update (July 20, 2019). The screenshot below was retrieved 01Aug2019 as reference but access that information here.

The following is offered to predict when Culex tarsalis will begin to fly across the Canadian prairies (Fig. 1). Protect yourself by wearing DEET!  This week, regions most advanced in degree-day accumulations for Culex tarsalis, the vector for West Nile Virus, are shown in the map below.  As of July 28, 2019, areas highlighted orange are on the verge of approaching sufficient heat accumulation for mosquitoes to emerge.  Areas highlighted red in the map below should now have C. tarsalis in flight.

Figure 1. Predicted development of Culex tarsalis, across the Canadian prairies (as of July 28, 2019).

Once adults emerge, the following map demonstrates how quickly a Culex tarsalis mosquito carrying WNV can become fully infective (i.e., when it has accumulated 109 base 14.3° degree days) – it’s a matter of days, depending on the region (Figure 2).  For example, as of July 28, 2019, Altona MB is predicted to only take 16 days for C. tarsalis to become fully infective!

Provincial Insect Pest Report Links

James Tansey, Scott Meers and John Gavloski
Categories
Week 17

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

Manitoba‘s Crop Pest Updates for 2019 are posted here. Access Issue #11 posted July 31, 2019, noting continued grasshopper issues, presence of some diamondback larvae and bertha armyworm pheromone trap interception counts that warranting in-field scouting in several regions of that province. There is also a call and link for Manitoban cooperators to perform the annual grasshopper counts. This a vital survey which contributes to the annual grasshopper forecast maps that growers depend upon to help assess risk.

Reminder – Saskatchewan‘s Crops Blog Posts includes a segment on “Economic thresholds” by Kaeley Kindrachuk posted in May 2019. Also access the Crop Production News with Issue #5 (featuring pesticide drift information).

•  Reminder – Alberta Agriculture and Forestry’s Agri-News includes an insect-related item in the July 8, 2019 edition with an important reminder that field scouting in July can lead to a more successful crop.

Crop reports

Jennifer Otani
Categories
Week 17

Crop reports are produced by:

The following crop reports are also available:

Field Events – Speak to an entomologist

Jennifer Otani
Categories
Week 17

Public summer field events – Coming to a field near you –  Prairie field crop entomologists are already scheduled to be at these 2019 field tour events from May-August (be sure to re-confirm dates and details as events are finalized):

  • August 8, 2019:  2019 Wheatstalk to be held at Teepee Creek AB.  View event info/registration details.   Entomologists tentatively participating: Jennifer Otani, Shelby Dufton, Amanda Jorgensen, Boyd Mori.
  • August 8, 2019. Horticulture School. Agriculture and Agri-Food Canada Research Farm, Portage la Prairie, Manitoba. View event info/registration details.  Entomologist presenting: John Gavloski, Kyle Bobiwash.

Previous Posts

Jennifer Otani
Categories
Week 17

Click to review these earlier 2019 Posts:

2019 Risk and forecast maps – Week 2

Alfalfa weevil – Week 11

Bertha armyworm (predicted development) – Week 12

Cabbage seedpod weevil – Week 11
Cereal aphid manager APP – Week 12
Cereal leaf beetle – Week 9
Crop protection guides – Week 6
Cutworms – Week 5

Diamondback moth – Week 15

Field heroes – Week 6
Flea beetles – Week 5

Grasshoppers – Week 10

Insect scouting chart for Canola – Week 5
Insect scouting chart for Flax – Week 5

Monarch migration – Week 13

Painted lady butterfly – Week 8
Pea leaf weevil – Week 10
Prairie Crop Disease Monitoring Network – Week 11
Preparing grains for market – Week 15

Ticks and Lyme disease – Week 4
Timely IOTW to review – Week 13

Weather Radar – Week 6
Wildfires – Week 8

Wind trajectories – Review Page for list of PDFs for Weeks 1-12

Monarch vs. Painted Lady

Jennifer Otani
Categories
Week 17

The case of the Monarch butterfly vs. Painted Lady butterfly (also Viceroy butterfly) An orange butterfly fluttered by. Was it a Monarch butterfly (Danaus plexippus)? Or a Painted Lady butterfly (Vanessa cardui)? If it’s a Monarch, it is species of Special Concern listed under the Species at Risk Act and is not a crop pest. Instead, it’s larvae feed solely on milkweed (Asclepias spp.), typically found in wetland areas. Painted Lady larvae, on the other hand, feed on a wider range of plants including sunflower, canola, mustard, borage, soybean, Canada thistle, burdock, knapweed, wormwood and many other plant species. While neither species overwinter in Canada, Monarchs have regular migratory routes into Canada from Mexico through the USA; Painted Ladies are accidental tourists that are on occasion blown up from the US. One important distinguishing characteristic is the distinct black band with white dots that outline the wings of Monarchs. Painted Ladies do not have this band; instead they have thin white markings along the scalloped wing edges.

Monarch butterfly (Danaus plexippus)
cc by sa 3.0 Kenneth Dwain Harrelson
Painted Lady butterfly (Vanessa cardui)
cc by 3.0 Jean-Pol Grandmont
Viceroy butterflies (Limenitis archippus)
cc by 2.0 Benny Mazur

Viceroy butterflies (Limenitis archippus) are even more difficult to tell from Monarchs. Viceroys are smaller than Monarchs and sport a black line running through the middle (side-to-side) of the hindwing. Like the Monarch, Viceroys are not crop pests as their larvae feed exclusively on trees of the willow family (willow, poplar, cottonwood). For more information about Painted Lady butterflies, see the Insect of the Week page and our posts on the annual Monarch butterfly migration.  The case of the innocuous versus the evil twin: When making pest management decisions, be sure that the suspect is 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 of monarch butterflies (Danaus plexippus) and viceroys (Limenitis achrippus).  Doppelgangers are usually relatively harmless but sometimes the doppelganger is a pest yet their behaviour, lifecycle or 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.

Review previously featured insects by visiting the Insect of the Week page.


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