Cabbage seedpod weevil

Jennifer Otani
Week 9

Cabbage seedpod weevil (Ceutorhynchus obstrictus) –  Reminder – 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.

CSPW emerge from overwintering in the spring as soil temperatures warm to ~15°C.  CSPW utilize several flowering hosts including wild mustard, flixweed, hoary cress, stinkweed and volunteer canola.  CSPW move to canola during the bud to early flower stages and will feed on pollen and buds, causing flowers to die.

The map below reflects CSPW densities observed in 2015.  Growers situated within or adjacent to areas of the map highlighted yellow, orange and red will need to be scouting with a sweep-net as their canola fields initiate flowering.

 ● 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.

Also watch provincial reports for updates on surveying underway now.  Alberta Agriculture & Forestry has released a new live CSPW map and online reporting tool for growers.  A screenshot (retrieved 29 Jun 2016) is included below.


Provincial Insect Pest Reports

Scott Meers, Scott Hartley, John Gavloski and prairiepest_admin
Week 9

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

– Manitoba’s Insect and Disease Update which includes alfalfa weevil and descriptions to aid scouting for cereal leaf beetle (June 22, 2016, prepared by John Gavloski and Pratisara Bajracharya).

– Saskatchewan’s Insect Report which mentions redbacked cutworms but emphasizes scouting for cabbage seedpod weevil, wheat midge and grasshoppers (Issue 4, prepared by Scott Hartley).
– Watch for Alberta Agriculture and Forestry’s Call of the Land for updates from Scott Meers  who recently provided an update (posted on June 23, 2016including cabbage seedpod weevil on early canola in southern Alberta, cereal leaf beetle reports on wheat and barley but also the benefits of its parasitoid, Tetrastichus julis.


Weekly Update

Jennifer Otani, David Giffen, Ross Weiss, Erl Svendsen, Kevin Floate and Owen Olfert
Week 9


A downloadable PDF version of the complete Weekly Update for Week 9 (June 29, 2016) can be accessed here.  

This edition includes the “Insect of the Week” featuring beneficial arthropods in 2016!

Subscribe to the Blog by following the instructions posted here!  You can receive automatic updates in your inbox through the growing season.

Questions or problems accessing the contents of this Weekly Update?  Please e-mail either Dr. Owen Olfert or Jennifer Otani.  Past “Weekly Updates” are very kindly archived to the Western Forum website by webmaster, Dr. Kelly Turkington.  


Weekly Update – Weather Synopsis

Ross Weiss, David Giffen and prairiepest_admin
Week 9

Staff are busy surveying so some maps are not available this week.

Warmer temperatures were observed throughout the prairies and the west was drier compared to the east.

The Accumulated Precipitation the past 7 days (June 22-28, 2016) is below:

The map below reflects the Accumulated Precipitation for the Growing Season so far for the prairie provinces (i.e., May 1-June 26, 2016):

Compared to last week, overnight temperatures were warmer during the past 7 days.  The map below shows the Lowest Temperatures the Past 7 Days (June 22-28, 2016) across the prairies:

The map below shows the Highest Temperatures the Past 7 Days (June 22-28, 2016):

The updated growing degree day map (GDD) (Base 5ºC, March 1 – June 26, 2016) is below:

While the growing degree day map (GDD) (Base 10ºC, March 1 – June 26, 2015) 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.


Weekly Update – Bertha Armyworm

Jennifer Otani
Week 9

Bertha armyworm (Lepidoptera: Mamestra configurataThis week, moths are expected to complete their yearly flight.  Reporting sites across the prairies have generally reported lower cumulative interceptions with some exceptions in Saskatchewan.  

Provincial staff coordinate BAW pheromone trapping across the prairies and summarize cumulative counts in report or map formats:
● Saskatchewanians.… Male moths have been intercepted at multiple sites in Saskatchewan with some sites reporting higher risk values (Insect Report-Issue #4, prepared by S. Hartley).  
● Manitobans.…. Low numbers of male moths have been intercepted throughout the province but review the values in the most recent Insect and Disease Report prepared by J. Gavloski and posted June 22, 2016.  

● Albertans.…..  Refer to the live 2016 map reporting Bertha armyworm pheromone trap interceptions.  A copy of the map (retrieved June 29, 2016) is below for reference.


Weekly Update – Grasshoppers

Ross Weiss and prairiepest_admin
Week 9

Grasshoppers (Acrididae) – Previous model predictions related to hatch and nymphal instar development can be reviewed here.  

The following image showing various stages of Camnulla pellucida is provided below – note that adults have wings extending the length of the abdomen whereas nymphs lack wings but develop wing buds that will eventually mature to wings.  

Generally, the economic threshold for grasshoppers in cereals is 8-12 per square metre but will vary by crop and growing conditions.

Figure 1. Life stages of Camnulla pellucida which including eggs, first-fifth instar nymphs and adult (L-R).
Biological and monitoring information related to grasshoppers in field crops is posted by the provinces of ManitobaSaskatchewanAlbertaBritish Columbia 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” – both English-enhanced or French-enhanced versions are available.

Weekly Update – Swede midge

Boyd Mori and prairiepest_admin
Week 9

Swede midge (Contarinia nasturtii)  – Reminder – Pheromone traps captured the first swede midge of 2016 between May 25 and 31 in northeastern Saskatchewan.  This is substantially earlier (6-7 weeks) compared to 2014 and 2015. 

The earlier emergence pattern is likely due to the mild winter and warm spring weather combined with adequate moisture levels. Emergence traps indicate a moderate number of swede midge have emerged near Carrot River, Saskatchewan, and producers should monitor their canola fields for damage symptoms

Figure 1. Swede midge infested canola buds which are enlarged with sepals fused together. 

Figure 2.  Swede midge large (~1mm long; yellowish-white) feeding within canola flower.

Swede midge scouting tips for in-field monitoring:
• Watch for unusual plant structures and plant discolourations then follow-up by closely scrutinizing the plant for larvae.
• The growing tip may become distorted and produce several growing tips or none at all, young leaves may become swollen, crinkled or crumpled and brown scarring caused by larval feeding may be seen on the leaf petioles and stems.
• Flowers may fail to open.
• Young plants that show unusual growth habits should be examined carefully for damage and larvae; especially if the sticky liners have many flies resembling midges (swede midges are about the size of orange blossom wheat midge but are not orange).
• Larvae can be seen with a hand lens.
• Refer to the Canola Watch article by Dr. Julie Soroka for more information on swede midge and watch for a new Ontario fact sheet produced by Baute et al. 2016.

Note the distribution map of confirmed symptoms and populations of swede midge (red dots) on the Canadian prairies  (Soroka and Andreassen 2015).


Weekly Update – Cereal leaf beetle

Jennifer Otani
Week 9

Cereal leaf beetle (Oulema melanopus) – Reminder – Back in May, the cereal leaf beetle (CLB) bioclimatic model was utilized to help predict when eggs and larvae might appear in fields along with its parasitoid, Tetrastichus julis

Recall the following (posted May 25, 2016) – Predicted dates of peak emergence of CLB eggs and larvae:

Cereal leaf beetle larvae hatch from eggs 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. 1).  When the larva completes its growth, it drops to the ground and pupates in the soil.  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.

Figure 1.  Larval stage of Oulema melanopus with characteristic feeding damage visible on leaf.

Give priority to following factors when selecting monitoring sites:
   □ Choose fields and sections of the fields with past or present damage symptoms.
   □ Choose fields that are well irrigated (leaves are dark green in color), including young, lush crops. Areas of a field that are under stress and not as lush (yellow) are less likely to support CLB. 
   □ Monitor fields located along riparian corridors, roads and railroads. 
   □ Survey field areas that are close to brush cover or weeds, easy to access, or are nearby sheltered areas such as hedge rows, forest edges, fence lines, etc.

Focus your site selection on the following host plant priorities:
   □ First – winter wheat. If no winter wheat is present then;
   □ Second – other cereal crops (barley, wheat, oats, and rye). If no cereal crops are present then;
   □ Third – hay crops. If no hay crops or cereal crops are present then;
   □ Fourth – ditches and water corridors

Sweep-net Sampling for Adults and Larvae:
 ● A sweep is defined as a one pass (from left to right, executing a full 180 degrees) through the upper foliage of the crop using a 37.5 cm diameter sweep-net. 
 ● A sample is defined as 100 sweeps taken at a moderate walking pace collected 4-5 meters inside the border of a field.  
 ● At each site, four samples should be collected, totaling 400 sweeps per site.  The contents of each sample should be visually inspected for life stages of CLB and all suspect specimens should be retained for identification.  
 ● Because the CLB larvae are covered in a sticky secretion, they are often covered in debris and are very difficult to see within a sweep-net sample. 
 ● To help determine the presence of CLB, place the contents of the sweep net into a large plastic bag for observation.

Visual Inspection:
Both the adults and larvae severely damage plants by chewing out long strips of tissue between the veins of leaves (Fig. 1), leaving only a thin membrane. When damage is extensive, leaves turn whitish. 

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 new “Field crop and forage pests and their natural enemies in western Canada – Identification and management field guide”.


Weekly Update – Alfalfa weevil

David Giffen, Owen Olfert and prairiepest_admin
Week 9

Alfalfa Weevil (Hypera postica) – The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer”.  The green larva featuring a dorsal, white line down the length of its body has a dark brown head capsule and will grow to 9mm long.  Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon).

Updated – Degree-day maps of base 9°C are now being produced by Soroka, Olfert, and Giffen (2016) using the Harcourt/North Dakota models.  The aim or the modelling is to predict the development of Alfalfa weevil (Hypera postica) across the prairies and to help growers time their in-field scouting as second-instar larvae are predicted to occur.  Compare the following predicted development stages and degree-day values copied below (Soroka 2015) to the map below.

For the week of June 26, 2016, the following map predicts the developmental stages for alfalfa weevil and corresponding degree-days.  Areas highlighted orange are predicted to find fourth instar larvae so scout for major leaf feeding then compare larval densities to the action threshold for alfalfa weevil!

Economic thresholds for Alfalfa weevil (adapted from Soroka 2015) vary by crop type (hay or seed), area fed upon and larval densities.

In hay fields, forage losses can be economic if one or more of the following symptoms are noted:
● if 25-50 % of the leaves on the upper one-third of the stem show damage, or
● if 50-70% of the terminals are injured, or
● if 1 to 3 third or fourth instar larvae occur per stem (with shorter stems having lower economic thresholds and 3 or more larvae requiring treatment no matter what the alfalfa height), or 
● 20-30 larvae per sweep occur when 12% leaf loss is acceptable.
● Also consider these two points:
      1. Early cutting of the first growth of alfalfa or insecticide treatment will reduce alfalfa weevil populations.
      2. If the hay crop value is high and weevil injury is seen or 2 or more larvae per stem reappear in regrowth after cutting, insecticide may be necessary (if a second cut is anticipated). 

In alfalfa seed fields:
● Economic thresholds are 20-25 third to fourth instar larvae per sweep or 35-50% of the foliage tips showing damage. 
● Thresholds increase with the height of the alfalfa, and decrease in drought conditions. 
● Also know that several small wasps parasitize alfalfa weevil larvae and adults, and in the past these natural control agents kept the weevil in check in most years. One of these wasps, Bathyplectes curculionis (Thomson), parasitizes alfalfa weevil in Alberta and Saskatchewan, and is now found in Manitoba.


Weekly Update – Small scarab beetle

Kevin Floate and prairiepest_admin
Week 9

Small scarab beetle (Coleoptera: Aphodius distinctus) – Reminder – This is the time of summer that farmers will be seeing larvae of a small scarab beetle (Aphodius distinctus) in their fields.  There have been scattered reports each June of large numbers of beetle grubs in crops associated with crop damage (e.g., canola, corn, dry bean, onion, pea).

Please help researchers compile information related to this species so they might confirm its pest status!  Information is posted about the beetle and the survey.  Here’s how you can help:

1. Please send reports of high white grub densities and associated crop damage to (403-317-2242). 

2. Live larvae accompanied by the following field information would be extremely helpful please – contact Dr. Kevin Floate if you have a sample!

3. Include answers to the following so the pest status for this species can be ascertained:  
     – Previous crop?
     – Legal land location or latitude+longitude?
     – Irrigated or not?
     – Was composted manure added this spring?
     – Surface residue in spring?


Weekly Update – Multitude of Mayflies!

Jennifer Otani
Week 9

Mayflies on your radar?!  Unusually large numbers – enough to repeatedly show up on eastern weather radar systems in North America, have been emerging and they’ve made the news!  

See and read more about mayflies on Bug Guide which is where this wonderful photo by Werner Eigelsreiter is posted.

Mayflies occur in rivers, streams, ponds and lakes and they are an important food source for several species of fish.  The aquatic nymph develops through several stages then moves to the surface to molt into a winged sub-adult that flies to nearby plants and molts again into an adult that usually live only for 48-72 hrs.  

Mayflies belong to the Order Ephemeroptera and you can see and read more about them on Bug Guide’s website.  

Insect of the Week – Rove beetle

Jennifer Otani
Week 9

Rove Beetle (predator and parasitoid)

Last year, the focus of the Insect of the Week was crop pests. This year, we’re changing things up and highlighting the many natural enemies that help you out, silently and efficiently killing off crop pests. [note: featured Insects of the Week in 2015 are available on the Insect of the Week page] 

This week’s Insect of the Week is the rove beetle (Delia spp.), is a generalist predator. The adult feeds on aphids, mites and larvae of many species under plant debris, rocks, dead animals, dung and other materials. The rove beetle larvae have similar hosts as the adult; the larvae of Aleochara spp parasitize various fly species including cabbage root maggot.

For more information about rove beetle, the pests it controls and other important crop and forage insects, see the new Field Crop and Forage Pests and their Natural Enemies in Western Canada – Identification and Management Field Guide for identification, life cycle and conservation options (download links for field guide available on the Insect of the Week page).

Adult rove beetle. (c) AAFC-Tyler Wist