Cabbage seedpod weevil

Jennifer Otani
Week 10

Cabbage seedpod weevil (Ceutorhynchus obstrictus) –  Reminders for 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.

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 06 Jul 2016) is included below.


Provincial Insect Pest Reports

John Gavloski, Scott Meers, Scott Hartley and prairiepest_admin
Week 10

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 (July 4, 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 July 7, 2016). 

Insect of the Week – Bertha armyworm parasitoids

Jennifer Otani
Week 10

Bertha armyworm parasitoids – Ichneumonids and Tachinids

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 Insects of the Week are tachinids, and ichneumonidae. The adult tachinid will feed on flower nectar, honeydew from aphids, scales, and mealybugs. The tachinid, Athrycia cinerea (Coq.), is a parasitoid of the Bertha armyworm. Ichneumonidae adults also eat nectar and aphid honeydow, however, its larvae (Banchus flavescens, Cresson) are parasitoids of Lepidoptera, Coleoptera, Diptera, Hymenoptera, and some spiders. 

For more information about these parasitoids, the other pests they control 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).

Ichneumonid – adult (Banchus flavescens). © John Gavloski, Manitoba Agriculture

Tachinid- adult. © Alberta Agriculture and Rural Development


Weekly Update

Jennifer Otani
Week 10

This week, Staff at Saskatoon and Beaverlodge are surveying.  The Weekly Update will be available Friday morning.

Tip: If we’re surveying in fields, you should be too!

Weekly Update

Jennifer Otani, David Giffen, Ross Weiss, Erl Svendsen and Owen Olfert
Week 10


All our Staff are surveying
so a brief version of the Weekly Update is provided for the week of July 6th!

A downloadable PDF version of the complete Weekly Update for Week 10 (July 6, 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, Owen Olfert and prairiepest_admin
Week 10

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

The map below reflects the Accumulated Precipitation for the Growing Season so far for the prairie provinces (i.e., May 1-June 30, 2016):

The updated growing degree day map (GDD) (Base 5ºC, March 1 – July 3, 2016) is below:

While the growing degree day map (GDD) (Base 10ºC, March 1 – July 3, 2016) 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 – Alfalfa weevil

David Giffen, Julie Soroka, Owen Olfert and prairiepest_admin
Week 10

Alfalfa Weevil (Hypera postica) – Please refer to earlier posts to find information related to the appearance, damage and biology of this insect pest.  

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 July 3, 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.

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 – Cereal leaf beetle

Jennifer Otani
Week 10

Cereal leaf beetle (Oulema melanopus) – Reminder – Please refer to earlier posts for information
related to the biology, damage and monitoring of the Cereal leaf beetle.

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 – Previous Posts

Jennifer Otani
Week 10

The following is a list of previous 2016 Posts – click to review:

Crop reports

Cereal leaf beetle

Bertha armyworm development and flight
Swede midge
Canola scouting chart
Wind trajectories
Flea beetles in canola
Predicted cereal leaf beetle development
Predicted lygus bug development
Predicted wheat midge development
Pea leaf weevil monitoring
Crop protection guides
Using Environment Canada’s radar maps to follow precipitation events
Iceburg reports
Multitude of mayflies

Monarch migration


Weekly Update – Wheat midge

Ross Weiss, David Giffen, Owen Olfert and prairiepest_admin
Week 10

Wheat Midge (Sitodiplosis mosellana) – Predictive modelling will be used again to help  forecast wheat midge emergence across the Canadian prairies.  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.