Questions of the Week

PEST update: diamondback moth (DMB)

A reminder that DBM move through life stages more quickly in warm weather. We probably won’t see as many generations as we did last year, but with the long-term forecast temps between 25-30°C for most of the next two weeks, we could see an increase in local DBM populations, where present. Natural enemies can provide rapid control, but repeated scouting may be required for this potentially multi-generation insect. Walking a field may turn up some larvae, but remember that the economic threshold is based on larvae/m², not sweep sampling. Pull plants and strongly tap them to dislodge larvae onto a tray or drop cloth to accurately assess the number of larvae. The action threshold is 100-150 larvae/m² in immature to flowering canola plants or 200-300 in flowering/podding plants (in dense stands). DBM updates by province: Manitoba, Saskatchewan, Alberta.

PEST update: bertha armyworm (BAW)

Catches in BAW monitoring traps continue to be counted across the Prairies. There are now several notable ‘warm’ spots for populations across the Prairies. Traps in Fairview, Vulcan and Lethbridge (AB) have moved into the ‘medium’ risk category, but numbers have not yet reached 600. Traps in Estevan and Kerrobert (SK), and Killarney (MB) have had trapped female numbers near or exceeding 300, which is deemed ‘uncertain risk, scouting advised’. Note that the trap network is well designed to capture regional trends but can miss higher numbers in individual fields across the Prairies.  

Peak emergence is later than normal this year in some regions due to cooler weather in late spring and early summer. Adult emergence is followed by egg laying and the destructive larval stage, so scout carefully. Check leaves for feeding: if BAW are present in a field at this time of year, they will be consuming green leaf material lower in the canopy and will move up and eat pods once leaves are consumed or have dropped off. Regional BAW outbreaks tend to last for two to three years, with eight to 10 years between, although there have not been any larger outbreaks in recent years. Economic threshold tables for BAW provide clear guidance based on cost of application and crop value. BAW updates by province: Manitoba, Saskatchewan, Alberta.

How to use ground truthing / satellite imagery for early insight on yield?

In-season – even early season – imagery of crop growth can be a strong predictor of yield. Areas of higher and lower biomass correspond to crop health and, so long as crop health remains consistent through the end of the growing season, yield. Satellite imagery provides a ‘big picture’ overview of crop health and is a good starting place to guide an in-field agronomic assessment. Once stronger and weaker areas of the crop are identified, calculate an approximate yield prediction by the percent of the total field that shows high, mid and lower biomass. Satellite imagery is more accessible than ever: a subscription can be relatively inexpensive, can be sent directly to any smartphone on a near-daily basis (barring cloud cover) and is available in all regions. Most crop input suppliers, grain buyers and agronomists can recommend a provider. (How to use technology to manage yield) (Why is this canola crop greener on one side of the field)

Prepped for disease scouting?

It will soon be the best timing for scouting canola disease.

• For general  canola disease scouting: download or request a hard copy of the Canola Disease Scouting Guide, then watch the Canola Disease Scouting video for a quick refresher, use the disease Fundamentals articles for details, and reference this handy Quick comparison of stem diseases table. 
• For sclerotinia: use the NEW Sclerotinia risk assessment tool to assess severity ratings at 30-60% SCC, checking the sclerotinia rating method video and using the photo gallery to recall rating specifics. Also remember to sign up for a  Saskatchewan disease training day and submit sclerotinia samples to support this research. 
• For blackleg: the Blackleg Yield Loss Calculator  can estimate potential yield loss based on severity and incidence, while the Management Guide to help you plan for future canola fields, along with the ‘How to interpret blackleg race test results’ video.
• For clubroot: watch this 1-min video before heading to scout, use the Management fact sheet to learn how to keep spores low and local, and watch this short (<2min) management summary video.  The Resistance Guide can help with future plans. 
• For verticillium stripe (VS): review this VS identification video, bring along your VS Field Scouting Guide  when scouting, and watch this How to collect samples for VS testing video. Experienced scouts have report this disease can be more apparent at or after typical swath timing, but that cutting root cross-sections 2-3″ below the ‘rootneck’ (ground level) can show the first visual clue of verticillium stripe’s presence: a grey starburst shape in the white root tissue.

For any canola disease resource inquires, contact Taryn Dickson.