Weekly Update (Jun 28, 2018; Wk 08) Otani, Weiss, Giffen, Meers, Barkley, Floate, Catton, Svendsen, Vankosky, Olfert

Greetings!

Field crop entomologists across the prairies are on the move with surveying and at field events.  Access the complete Weekly Update either as a series of Posts for Week 08 (June 28, 2018) OR a downloadable PDF version.  Also review the "Insect of the Week" for Week 8!

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 three steps!

Weather synopsis (Jun 28, 2018; Wk 08)

Weather synopsis – This week staff have been busy at field events and surveying so we direct you to the AAFC Drought Watch maps.  

Accumulated precipitation for the past seven days (June 27, 2018) is available from Agriculture and Agri-Food Canada (Fig. 1).

Figure 1.  Precipitation across the Canadian prairies the past seven days (June 27, 2018).Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (28Jun2018).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1529635048320).

Accumulated precipitation for the growing season (April 01-June 27, 2018) is available from Agriculture and Agri-Food Canada (Fig. 2).

Figure 2.  Precipitation across the Canadian prairies for the current growing season (April 1-June 27, 2018).Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (28Jun2018).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1529635048320).

The map below reflects the Highest Temperatures occurring over the past 7 days (June 27, 2018) across the prairies and is available from Agriculture and Agri-Food Canada (Fig. 3). 

Figure 3.  Highest temperature across the Canadian prairies the past seven days (June 21-27, 2018).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (28Jun2018).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1529635048320).

The map below reflects the Lowest Temperatures occurring over the past 7 days (June 21-27, 2018) across the prairies and is available from Agriculture and Agri-Food Canada (Fig. 4).

Figure 4.  Lowest temperature across the Canadian prairies the past seven days (June 21-27, 2018).Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (28Jun2018).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1529635048320).

The growing degree day map (GDD) (Base 10ºC, March 1 – June 24, 2018) is below:

The growing degree day map (GDD) (Base 5ºC, March 1 – June 24, 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.

Predicted grasshopper development (Jun 28, 2018; Wk 08)

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 24, 2018, the warm weather has resulted in rapid grasshopper development for populations near Saskatoon SK. Model output for Saskatoon predicts that hatch is complete and that populations are primarily in the 4th instar stage (Fig. 1). By comparison, last week’s model output indicated that populations should be primarily in the 2nd and 3rd instar stages. 

Figure 1.  Predicted grasshopper phenology at Saskatoon SK.
Values are based on model simulations for April 1 – June 24, 2018.

Grasshopper Scouting Steps: 

● Measure off a distance of 50 m on the level road surface and mark both starting and finishing points using markers or specific posts on the field margin.

● Starting at one end in either the field or the roadside and walk toward the other end of the 50 m making some disturbance with your feet to encourage any grasshoppers to jump. 

● Grasshoppers that jump/fly through the field of view within a one meter width in front of the observer are counted. 

● A meter stick can be carried as a visual tool to give perspective for a one meter width.  However, after a few stops one can often visualize the necessary width and a meter stick may not be required. Also, a hand-held counter can be useful in counting while the observer counts off the required distance. 

● At the end point the total number of grasshoppers is divided by 50 to give an average per meter. For 100 m, repeat this procedure. 
● Compare counts to the following damage levels associated with pest species of grasshoppers:

0-2  per m² - None to very light damage

2-4  per m² - Very light damage

4-8  per m² - Light damage

8-12 per m² - Action threshold in cereals and canola

12-24 per m² - Severe damage 

>24 per m² - Very severe damage

* For lentils at flowering and pod stages, >2 per m² will cause yield loss.

* For flax at boll stages, >2 per m² will cause yield loss.

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 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 (Jun 28, 2018; Wk 08)

Bertha armyworm (Lepidoptera: Mamestra configurata) - As of June 24, 2018, BAW development continues to be 7-10 days ahead of normal development (Figs. 3 A and B). Pupal development is complete across the prairies (Fig. 1).

Near Saskatoon SK, BAW egg hatch is nearly complete and larvae are present (Fig. 2). Based on Long Term Climate Normal (LTCN) data, larvae generally begin to occur the last few days of June (Fig. 3).

Figure 2. Predicted BAW phenology at Saskatoon SK.
Values are based on model simulations for April 1 – June 24, 2018 and B) Long term climate normals.

Figure 3.  Predicted BAW phenology at Saskatoon SK.
Values are based on model simulations for Long Term Climate Normals (LTCN).

Many thanks to those who are checking a bertha armyworm pheromone trap on a weekly basis.  Please use the reference photo below 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.  Check carefully and thanks for your help!

Monitoring:
- Larval sampling should commence once the adult moths are noted. 
- Sample at least three locations, a minimum of 50 m apart. 
- At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae. 
- Count them and compare the average against the values in the economic threshold table below:  

Scouting tips:
● Some bertha armyworm larvae remain green or pale brown throughout their larval life. 
● Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms. 
● Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves. 
● Larvae eat the outer green layer of the stems and pods exposing the white tissue. 

● At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.

Keep track of the Provincial Entomologist Updates for the latest in-season pheromone trap monitoring results for 2018.  

Albertans can access the online reporting map (screenshot retrieved 28Jun2018 provided below for reference:

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 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 (Jun 28, 2018; Wk 08)

Wheat Midge (Sitodiplosis mosellana) – As of June 24, 2018, the recent dry conditions near Saskatoon SK have resulted in delayed emergence of  adult wheat midge (Figs. 1 and 2).  Predictions for 2018 are similar to average values (Figs. 2 and 3). 

Figure 1.  Predicted wheat midge emerged based on degree-days accumulated across
the Canadian prairies (as of June 24, 2018).

Figure 2.  Predicted wheat midge phenology at Saskatoon SK.
Values are based on model simulations for April 1 – June 24, 2018.
Model projections to July 15 are based on long term climate normal values for temperature and precipitation.

Figure 3.  Predicted wheat midge phenology at Saskatoon SK.
Values are based on model simulations for Long Term Climate Normals (LTCN).
Model projections to July 15 are based on long term climate normal values for temperature and precipitation.

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. 

Click here to review the 2018 wheat midge forecast map.  

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.

Lygus in canola (Jun 28, 2018; Wk 08)

Lygus bugs (Lygus spp.) - As of June 24, 2018, the Lygus model suggests that Saskatoon populations should consist of mostly 4th instar nymphs (Fig. 1). Predicted development for the 2018 growing season is greater than for development that is based on long term climate normals (Fig. 2).

Figure 1.  Predicted Lygus phenology at Saskatoon SK.
Values are based on model simulations for April 1 – June 24, 2018.

Figure 2.  Predicted Lygus phenology at Saskatoon SK.
Values are based on model simulations for Long Term Climate Normals.

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.

Repeat the sampling in another 14 locations. 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-enhanced or French-enhanced versions are available.

Cabbage seedpod weevil (Jun 28, 2018; Wk 08)

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.

Monitoring:  
 ● 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.

Albertan growers can report and check the online map for CSPW posted by Alberta Agriculture and Forestry (screenshot is provided below for reference; retrieved 28Jun2018).

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

Request for Cereal Leaf Beetle Larvae (Jun 28, 2018; Wk 08)

Reminder - Researchers need your help - They are looking for LIVE cereal leaf beetle larvae from any field across the Canadian prairies in order to assess Tetrastichus julis parasitism rates.

If larvae are encountered in 2018, please carefully collect 20-30 of them and put them with some cereal leaves and a moist paper towel in a hard container (e.g. plastic yogurt container) with holes poked in the lid for air. Pack the parcel with ice packs, label with your name, date, crop type, and location, and send them to us.  Email or phone us for information on how to ship for free.

What's in it for you? Learn if cereal leaf beetle is being controlled by natural enemies in your field. If you need T. julis, we may be able provide you with some.

Contact:
Dr. Haley Catton, Agriculture and Agri-Food Canada
5403 - 1 Ave S, Lethbridge, Alberta T1J 4B1
403-317-3404, haley.catton@canada.ca

Pea leaf weevil (Jun 28, 2018; Wk 08)

Pea Leaf Weevil (Sitona lineatus) – As of June 24, 2018, the PLW model predicted that hatch is nearly complete and the population is primarily in the larval stage in the Saskatoon area (Fig. 1).  Development in 2018 is faster than long term average (Fig. 2).  

Figure 1.  Predicted pea leaf weevil phenology at Saskatoon SK.
Values are based on model simulations for April 1 – June 24, 2018.

Figure 2.  Predicted pea leaf weevil phenology at Saskatoon SK.
Values are based on model simulations for Long Term Climate Normals (LTCN).

Pea leaf weevil larvae develop under the soil over a period of 30 to 60 days. They are “C” shaped with a dark brown head capsule. The rest of the body is a milky-white color (Fig. 3 A). Larvae develop through five instar stages. In the 5th instar, larvae range in length from 3.5 - 5.5 mm. First instar larvae bury into the soil after hatching, and search out root nodules on field pea and faba bean plants. Larvae enter and consume the microbial contents of the root nodules (Fig. 3 B). These root nodules are responsible for nitrogen-fixation, thus pea leaf weevil larval feeding can affect plant yield and the plant’s ability to input nitrogen into the soil. 

Figure 3.  Pea leaf weevil larva in soil (A) and field pea root nodules damaged by larval feeding (B).  Photos: L. Dosdall).

Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol.

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.

White grubs in field crops (Jun 28, 2018; Wk 08)

Scarabaeidae – Reminder - Each June brings scattered reports across the Prairies of white grubs associated with crop damage.  In fact, several species of Aphodius, Phyllophaga, Polyphylla or even small Aetenius produce larvae described as "white grubs".  

Recently, crop damage reports have been associated with a grub identified as the larvae of the beetle Aphodius distinctus (see below). This common beetle is not known to be a pest, but there is an ongoing effort to gather information to develop a ‘pest’ profile.  Additional information is online at Top Crop Manager. Please send reports of this insect and associated information to Dr. Kevin Floate (Agriculture and Agri-Food Canada, Lethbridge, AB).

Field Heroes (Jun 28, 2018; Wk 08)

As crops continue to grow, please consider the vital role beneficial organisms have in your fields.  Please make use of the Scouting Guides freely available on the Field Heroes website.  Each guide includes valuable information and photos to help identify the contents of a sweep-net and to increase understanding of the impact of beneficial insects. Please share and encourage use of the Scouting Guides.

Be sure to follow @FieldHeroes on Twitter for practical tips and information. Please tag @FieldHeroes in your own Tweets about beneficials. Re-Tweets are great, too.

Thanks to Western Grains Research Foundation for their support of this important campaign. This initiative is not possible without the support and advice of enthusiastic members of the Prairie Pest Monitoring Network. Our research is having a tangible impact on growers’ pest management decisions.

Link here to access a complete list of all the PPMN Blog Posts related to Natural Enemies!

Monarch migration (Jun 28, 2018; Wk 08)

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 28Jun2018) but follow the hyperlink to check the interactive map.  They are in Manitoba and moving west through southern Saskatchewan this week!

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.  

West Nile Virus and Culex tarsalis (Jun 28, 2018; Wk 08)

West Nile Virus Risk –  The regions most advanced in degree-day accumulations for Culex tarsalis, the vector for West Nile Virus, are shown in the map below.  Areas highlighted yellow then orange are approaching sufficient heat accumulation for mosquitoes to emerge while mosquitoes will be flying in areas in red so wear DEET to stay protected!

Health Canada posts information related to West Nile Virus in Canada.  Health Canada also tracks WNV through human, mosquito, bird and horse surveillance.  The 2017 WNV surveillance map for human cases is available here but a screenshot is posted below for reference.

Figure 1.  As of surveillance week 49, ending December 9, 2017, the preliminary data indicated 197 human cases of WNV in Canada; twenty-five from Québec, 159 from Ontario, five from Manitoba, seven from Alberta, and one from British Columbia.

The Canadian Wildlife Health Cooperative compiles and posts information related to their disease surveillance for West Nile Virus in birds.  As of June 28, 2018, 642 birds were examined and zero have tested positive for West Nile virus.