Agronomist Notes

We hosted a controlled traffic field day at the farm last Thursday and had a good turnout in spite of the hot, humid conditions. Forty-five people from Barrhead to Medicine Hat came for the tour to look at the equipment modifications, discuss challenges and share ideas. We had a great afternoon and I can see it becoming an annual event.

I’ve been scouring my territory for diseases and insects and have found very little of either. I did find a trace amount of stripe rust near Beiseker on a few flag leaves. I’ve found very few lygus bugs and diamondback moths so far. I suspect that lygus bugs will not be a problem this year which leaves diamondback moths and bertha armyworms to watch for.

This week we’ll look at a unique way to boost canola yields by applying liquid urea after petal drop. Next, I’ve provided some info and comments on leaf senescence in cereals and what to watch for. Since stripe rust may be a problem in some areas outside my territory, I’ve included a summary on scouting techniques, thresholds and control options. We’ll look at some tips for scouting lygus bugs and finish with estimating yield loss from leaf diseases in cereals. Fundamental and technical grain market news will conclude this week’s issue.

Crop Staging (Calgary to Drumheller to Three Hills)

Seeded	April 23-31	May 1-7	May 8-15
Wheat	milky dough	watery ripe	watery ripe
Canola	early pod	late bloom	late bloom
Barley	milky dough	milky dough	watery dough
Peas	pod fill	end of flower	end of flower

Steve’s tips for the week

• Continue monitoring canola for diamondback moths.
• Continue sweeping for lygus bugs in canola. Threshold is 3 per sweep.
• If you plan to straight cut canola, watch the fields as they come out of bloom to give you an idea of which ones are the most even and best candidates for straight cutting.
• Monitor leaf senescence in wheat and barley to watch for disease and pre-mature ripening. 

Agronomy

Applying liquid urea at early pod stage in canola boosts yields

During my visit to the UK last November I discovered an interesting way to boost yield in canola. A few producers have started to apply liquid urea at the early pod stage, a time when nitrogen may be limiting. The results have been a 7 to 9 bu/ac yield increase from 25 lbs actual nitrogen using a liquid urea solution, which is roughly a 10% yield increase. I think a quick tissue test for nitrogen at the end of flowering could show you whether nitrogen is limiting in the plant. If there is adequate moisture in the soil profile, a liquid top dress of urea might be a new avenue to explore in our canola production systems. 

The majority of producers are using liquid urea instead of liquid UAN (28-0-0) for its lower cost, increased uptake efficiency and very little leaf burn. Liquid urea is unique because it is the only nitrogen molecule small enough to fit through the stomata and the ectodesmata (leaf pores), the main entry points for nutrient uptake. Targeting the stomates as your sole point of entry for foliar nutrients is difficult because stomates will open and close multiple times throughout the day as they respond to sunlight, darkness, moisture and temperature. Also, the majority of stomata in canola are located on the underside of the leaf where very little solution will find its way. That leaves the ectodesmata as the entry point for urea nitrogen.There are plenty of ectodesmata located on the top and bottom of the leaves and the urea molecule is small enough (0.88 nm) to fit through the 1 nm opening.

I chatted with my good friend Nick Ward from Lincolnshire and asked him how he applied liquid urea to his canola. Here are his comments:

• You can use any 46% urea and tip it into the water tank and circulate it using a pump. 'Distressed' urea is usually used (ie. sweepings up out of a boat or store) as it is cheaper and doesn't need to have spreading quality.
• We spray on 150-200 litres of 20% nitrogen solution per ha at the end of flowering. (That works out to 25 lbs/N per 15-20 US gallons/ac.)
• If temperatures are hot, apply in the evening. We don't dilute it, but if you were concerned about heat, dilute it with the same amount of water. I've applied the urea solution up to 23 degrees C and didn't have any problems with leaf burn.
• 20% is the max strength that you will get. I think granular urea may be the better option as prilled has an oily coating that leaves a film on the liquid.
• For our main liquid fertilizer solutions we would use an ammonium nitrate/urea mix in solution to get the concentration up to 37%. But for this job a urea solution is a lot gentler and will cause way less scorch even in warmer conditions.

Here are a couple of points of my own:

• Add 3.6 lbs of urea per gallon of water to give you 25 lbs/N per acre and apply solution at 15 gal/ac.   
• You can delay maturity with a late season nitrogen application so those who’ve finished flowering by late July, early August might be able to afford a slight delay in maturity.

Steve’s quick math

Let’s see what this nitrogen boost could pay back.
25 lbs/ac x $0.45 lb/N: $11.25 ac + $3.50 application = $14.75
50 bu/ac canola yield x 10% x $10.00 bu = $50.00 ac
ROI: 239%

In theory, if we were to see the same response as some have in the UK, the additional $14.25 investment in liquid urea may net you a 239% return on your investment. I think there is value in spreading out your nitrogen applications in canola and this might be a way to generate better nitrogen use efficiency rather than applying all of our nitrogen up front which by now is 90 days ago. Even a 5% yield increase at today’s prices makes this option viable. I would love to see someone try this. Let me know if you give it a go! SL

Stripe rust identification and control

Thankfully the infection level and incidence of stripe rust has been minimal at this time. I’ve found trace amounts of stripe rust in the Beiseker area in my travels last week. I found it on AC Harvest but only along one headland on a few flag leaves. Surprisingly, a winter wheat crop (most susceptible) a few miles away had none. Most wheat crops in my territory are well past the flowering stage and applying a fungicide is no longer economical but if crops are later in your area, keep reading for more on this disease.

Identification and yield loss

Stripe rust can be identified as small orange-yellow coloured pustules forming in vertical lines along wheat leaves. This disease can result in yield losses of 10 to 70% in susceptible varieties and total yield loss has been reported when severe epidemics occur. Like other leaf and stem diseases, yield losses are roughly proportional to the plant area infected. Yield losses are generally most severe when the infection occurs prior to heading. Historically stripe rust has not been of economic significance in western Canada but incidences of the disease have been increasing over the past 4 or 5 growing seasons.

Conditions for development

The major source of rust spores in Alberta is carried by south winds from the Pacific North West. Wind direction and a specific range of temperatures are essential for the onset and development of stripe rust. For example, relative low temperatures and moisture favour development. Urediniospores germinate optimally between 5 and 15oC with limits near 0 and 20oC. Disease development is most rapid between 10 and 15oC with intermittent rain.

Monitoring

If you are growing a susceptible variety, it is important to scout every few days starting with the bottom leaves. Know the visual symptoms of stripe rust and monitor fields in the morning when new spores are distinctly yellow. See stripe rust tolerance ratings below.

Threshold

Spraying should be done when stripe rust reaches 1% of flag leaf area and before it reaches 5% of flag leaf area. Once this infection level is reached, stripe rust becomes very difficult to control. The period of infection to the release of spores is as little as 8 days, which can result in multiple generations per growing season.

Growth stage

Apply fungicide at flag leaf or before wheat has flowered. Fungicide treatments made past the flowering stage rarely provide an economical benefit.

Fungicide Options

Folicur: 118 ml/ac $10.50/ac:  Best option for stripe rust control
Quilt: 300 ml/ac $10.40/ac
Headline: 160 ml/ac $11.00/ac
Tilt: 202 ml/ac $7.00/ac
Stratego: 200 ml/ac $7.60/ac

Stripe Rust Tolerance Ratings

HRSW http://www.agric.gov.ab.ca/app95/loadCrop?action=display&id=58
CPS http://www.agric.gov.ab.ca/app95/loadCrop?action=display&id=56
FAQ’s http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/faq11389

Source: AAFRD

Tips on lygus bug scouting

Many canola fields are just about finished blooming and now coming into the stage where lygus bugs can damage canola. I haven’t found any fields even close to threshold after all the rain this year but there may be pockets with high lygus bug pressure. To help you make the decision whether to spray or not this year, I've put together a few pointers. 

Lygus bugs will typically damage 7% of the seed at the 3 to 4 per sweep threshold. That's 2 bushels damage on a 30 bushel crop, 2.8 bushels on a 40 bushel crop and 3.5 bushels on a 50 bushel crop. Under heavy infestations, yield loss estimates have been as high as 40%.

First: Identify the maturity of the lygus bugs. Count the number of fourth and fifth instar lygus bugs there are per sweep, which are the ones that do the damage. Lygus bugs at the 1st to 3rd instar do not have the ability to pierce the pods and cause damage. If you count more than 3 to 4 mature lygus bugs per sweep then move on to the second step.

Second: Identify the firmness in the seeds. Lygus bugs have piercing sucking mouth parts, but they cannot pierce through firm seeds or pods. Select a few plants at each stop and open up the pods to see how firm the seeds are inside. Then, estimate the percentage of watery or translucent seeds in the plant.

Last: If the mature lygus bug counts have reached 3 to 4 per sweep, not including young lygus bugs and more than 1/3 of the seeds in the pods are watery or translucent, then control is necessary. Reversely, if more than 2/3 of the seeds are firm and the threshold level has just been reached, you're likely out of the danger zone and don't need to spray.SL

Reference and photo source: Alberta Agriculture and Canola Council of Canada http://www.canolacouncil.org/chapter10b.aspx

Estimating loss from crop disease after the fact

By now we've made the decision to spray or not to spray for leaf diseases in cereals. We are quickly approaching the point to which you can actually estimate whether your decisions were correct or, sadly, not.

To estimate yield loss from net blotch, scald, tan spot or septoria, examine the crop at the soft dough stage. Assess at least 25 main stems in four areas off the head. Then estimate the average percentage of the top two leaves affected. The calculation for percent yield loss is (0.66 × percentage of flag leaf infected) + (0.5 × percentage of second leaf infected) ÷ 2.

Steve’s quick math

You find disease present in wheat on 10% of the flag leaf and 20% on the leaf below.
Percent yield loss in wheat/malt barley = (0.66 x 10) + (0.5 x 20) ÷ 2 = 8.3%
Therefore, your calculated yield loss is 8.3% in both wheat and malt barley. At $5.50/bu wheat and $3.50/bu malt barley with a yield potential of 55 bu/ac and 80 bu/ac respectively, you have lost 4.5 bu/ac in wheat and 6.6 bu/ac in malt barley. That loss translates to $24.75/ac for wheat and $23.10/ac for malt barley at today’s prices.

The cost of a fungicide including application is roughly $14.25/ac for a product like Tilt or Stratego. So, the return on your fungicide investment in wheat would have been 73.6% [($24.75/ac - $14.25) ÷ 14.25 x 100]. The return on your investment in malt barley would have been 62% [($23.10/ac - $14.25) ÷ $14.25 x 100]. In this scenario the $14.25 ac investment netted us between $8.85 ac and $10.50 ac. So, in hindsight a fungicide would have definitely offered a decent return on investment this year. Take note of disease pressure, difference in crop rotations and the conditions we’ve experienced this year. From there you can make better decisions in the years to come. Happy scouting. SL