Weekly Update

Taylor Kaye, Jennifer Otani, Owen Olfert, Erl Svendsen, David Giffen and Ross Weiss
Week 15


A downloadable PDF version of the complete Weekly Update for Week 15 (August 10, 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, Owen Olfert, David Giffen and Erl Svendsen
Week 15

Weather synopsis – The average temperature over the past seven days (August 1-7, 2016) was approximately 1°C cooler than Long Term Normal (LTN).

Across the prairies the 7 Day Average Cumulative Rainfall was well above average (August 1-7, 2016)

The average 30 day temperature for July 8 to August 7 was similar LTN and rainfall was 50% greater than LTN (average across the prairies).

The average growing season temperature (April 1 – August 7) has been less than 1°C warmer than normal

Growing season rainfall has been approximately 27% above average.

The map below is the modelled soil moisture map for the prairies (up to August 7, 2016)

The map below reflects the 7 Day cumulative precipitation map (August 2 – August 8, 2016)

7 Day Accumulated Precip Aug 2-8.JPG

While the map below summarizes the cumulative precipitation for the growing season (April 1 – August 8, 2016).

Growing Season Accumulated Precip Apr 1-Aug 8.JPG
The updated growing degree day map (GDD) (Base 5ºC, March 1 – August 7, 2016) is below:

GDD Base 5 Aug 7

While the growing degree day map (GDD) (Base 10ºC, March 1 – August 7, 2016) is below:

GDD Base 10 Aug 7

The map below shows the Lowest Temperatures the Past 7 Days (August 2 – August 8, 2016) across the prairies:

7 Days Lowest Temp Aug 2-8.JPG
The map below shows the Highest Temperatures the Past 7 Days (August 2 – August 8, 2016):

7 Days Highest Temp Aug 2-8.JPG

Weekly Update – Pre-Harvest Intervals (PHI)

Jennifer Otani
Week 15

Pre-Harvest Interval (PHI) – Growers with late-season insect pest problems will need to remember to factor in the PHI which is the minimum number of days between a pesticide application and swathing or straight combining of a crop.  

The PHI recommends sufficient time for a pesticide to break down and a PHI-value is both crop- and pesticide-specific.  Adhering to the PHI is important for a number of health-related reasons but also because Canada’s export customers strictly regulate and test for the presence of trace residues of pesticides.

An excellent summary of PHI for various pesticides in their various crops was posted by Saskatchewan Agriculture this week within their Crop Production News.

In 2013, the Canola Council of Canada created and circulated their “Spray to Swath Interval Calculator” which was intended to help canola growers accurately estimate their PHI.  Other PHI are described in your provincial crop protection guides and remember that specific crop x pesticide combinations will mean different PHIs.  More information about PHI and Maximum Residue Limits (MRL) is available on the Canola Council of Canada’s website.


Weekly Update – Lygus in canola

Jennifer Otani
Week 15

Lygus bugs (Lygus spp.) – Reminder – 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.


Weekly Update – Swede midge

Jennifer Otani
Week 15

Swede midge (Contarinia nasturtii) The Swede midge bioclimate model was run for Melfort for 2015 and 2016 (April 1 – August 7). For 2015, model output indicated that the 2015 growing season would have resulted in two generations by the first week in August (first graph below).  For 2016, model output indicated that there has been potential for four generations in the 2016 growing season (second graph below). The extra generations in 2016 are explained by timing of rainfall. Adult emergence is delayed until a) the required number of degree-days are achieved and b) after at least 10 mm of rain has occurred (over a 7 day period). In 2015, low rainfall during April and May resulted in delayed emergence with first adults emerging in early June. A dry period in late June/early July was predicted to delay adult emergence until mid-July.  In 2016 May rainfall was predicted to result in adult emergence occurring during the second week of May and subsequent emergence in mid-June, mid-July and early August. 


Weekly Update – Grasshoppers

Ross Weiss, Owen Olfert, David Giffen and Erl Svendsen
Week 15

Grasshoppers (Acrididae) – Across the prairies the model indicates that 80% of the population should be in the adult stage. This is approximately 10% greater than average. Oviposition is predicted to be well underway with oviposition being the most advanced in MB and SE SK.

Msang Oviposition.jpg
The following graph shows predicted grasshopper development at Saskatoon for August 7, 2016


Cabbage seedpod weevil

Jennifer Otani
Week 15

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.

 ● 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.


Weekly Update – West Nile Virus and Culex tarsalis

David Giffen, Owen Olfert and prairiepest_admin
Week 15

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.  As of August 7, 2016areas highlighted in yellow, orange, or red on the map below have accumulated sufficient heat for C. tarsalis to fly so wear your DEET to stay protected!

GDD Base 14.3 Aug 7

The Public Health Agency of Canada posts information related to West Nile Virus in Canada.  The map of clinical cases of West Nile Virus in Canada in 2016 is posted (as of July 23, 2016) while a screen shot is provided below (retrieved August 10, 2016).

WN Cases Canada.jpg

The Canadian Wildlife Health Cooperative compiles and posts information related to their disease surveillance for West Nile Virus.  As of August 3, 2016, 27 birds were submitted for testing yet none have tested positive for West Nile virus. 


Provincial Insect Pest Reports

John Gavloski, Scott Meers, Scott Hartley and prairiepest_admin
Week 15

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 lygus in canola, grasshopper monitoring, and a few sites showing moderate risk levels for bertha armyworm based on pheromone trap interceptions (August 5, 2016, prepared by John Gavloski and Pratisara Bajracharya).

Saskatchewan’s Crop Production News includes pre-harvest intervals (PHI) for a long list of field crop pesticides in Issue 6prepared by Danielle Stephens.  As the report notes, “all pesticides have a PHI” specific for product and crop type.  The PHI prevents crops exceeding Maximum Residue Levels (MRL) that will affect the quality of seed in terms of export.

Watch for Alberta Agriculture and Forestry’s Call of the Land for updates from Scott Meers  who recently provided an update (posted on August 4, 2016).

Weekly Update – Crop reports

John Gavloski, Scott Meers, Scott Hartley and prairiepest_admin
Week 15

Crop reports are produced by:

– Manitoba Agriculture, Rural Development (August 8, 2016).
– Saskatchewan Agriculture Crop Report (August 2, 2016) which is also posted in a printer-friendly version.

– Alberta Agriculture and Forestry (for August 2, 2016).

This week, the USDA’s Crop Progress Report (posted August 1, 2016) which includes harvest and condition ratings for winter wheat, spring wheat, oat, barley, plus range and pasture conditions is available. 

The USDA also produces a World Agricultural Production Report (July 2016) which estimates production across the globe for corn, cotton, rapeseed, and wheat but also includes tabular data for other grains.


Weekly Update – Harvest Sample Program

Jennifer Otani
Week 15

The Canadian Grain Commission is ready and willing to grade grain samples harvested in 2016.  Samples are accepted up to November but send samples as soon a harvest is complete.

This is a FREE opportunity for growers to gain unofficial insight into the quality of their grain and to obtain valuable dockage information and details associated with damage or quality issues.  The data collected also helps Canada market its grain to the world!

More information on the Harvest Sample Program is available at the Canadian Grain Commission’s website where growers can register online to receive a kit to submit their grain.  

In exchange for your samples, the CGC assesses and provides the following unofficial results FOR FREE:
  • dockage assessment on canola
  • unofficial grade
  • protein content on barley, beans, chick peas, lentils, oats, peas and wheat
  • oil, protein and chlorophyll content for canola
  • oil and protein content and iodine value for flaxseed
  • oil and protein for mustard seed and soybeans
Many producers find having both grade and quality information on their samples before delivering their grain to be helpful.

Weekly Update – Previous Posts

Jennifer Otani
Week 15

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

Alfalfa weevil
Aphids in canola 

Bertha armyworm development and flight
Bertha armyworm

Cabbage root maggot
Canola scouting chart
Cereal leaf beetle
Crop protection guides

Diamondback moth

Environment Canada’s radar maps to follow precipitation events

Flea beetles in canola


Iceburg reports

Insects in our diet

Monarch migration

Pea leaf weevil monitoring

Predicted lygus bug development
Predicted wheat midge development

Swede midge

Thrips in canola

Weather Synopsis (Week 12)

Wheat midge
Wind trajectories


Insect of the Week – Natural predators

Jennifer Otani
Week 15
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] 
Natural enemies don’t just appear from nowhere – they rely on nearby
non-crop and (semi-)natural sites for shelter, food, overwintering sites and
alternate hosts for when crop pests are either not present or in low numbers.
How you manage these sites can have a huge impact on natural enemies’ capacity
to supress pests when you need them to. These same sites are also essential
habitats for pollinators, important for maximizing yield of non-cereal seed
crops (e.g. oil seed crop). A recent publication, ‘Agricultural practices that
promote crop pest suppression by natural predators’, describes the role of
non-crop areas and management practices to nurture natural enemy populations.
Go to the Insect of the Week page for download links for
this publication. There you will also find more information about natural
enemies, the pests they control and details about important crop and forage
pest insects by downloading the new Field Crop and Forage Pests and their
Natural Enemies in Western Canada – Identification and Management Field Guide.