July 2, 2013

Agronomist Notes

Hello Reader

Wow, another inch of rain, bringing us to just over 200 mm (8 inches) in the last 40 days. Soils are saturated but crops are now reaching peak demand at 7mm/day so we’ll be using up soil moisture quickly. Barley and canola crops are suffering the most from low oxygen levels in the soil but will recover if the rains stay away.

We’re now applying fungicides in peas, wheat, barley and canola. Everything seems to be ready at once with a huge number of acres getting a treatment in the next ten days. Crops are progressing quickly and for this agronomist, it’s everything I can do to stay on top of the staging. Thirty degrees Celsius combined with 70% humidity and 18 hours of daylight is like giving these crops a shot of nitrous oxide. The weather is supposed to cool back down to low 20’s with scattered showers and hail storms. What a year!

This week we’ll cover as much as we can on canola staging, insect sweeping and fungicide timing. We’ll look at a temperature and humidity chart that tells you how hot is too hot to spray pesticides so you can maintain fungicide efficacy in this hot weather. I’ve included a list on our upcoming CTF field day next week on Thursday, July 11th. We’ll finish with technical grain market news.

Photo: Fababeans planted May 9 just starting to bloom, near Morrin, AB. S. Larocque

Crop Staging

(Calgary to Drumheller to Three Hills)

Seeded May 1-7 May 8-15 May 15-22
Wheat heads emerging flag leaf 2nd node

Canola 20% bloom 5% bloom bolting

Barley heads emerging flag leaf 2nd node

Peas early flower 12th node 10th node

Steve's tips & tricks of the week

Follow me on Twitter for in-season updates @BeyondAgronomy

Continue post-herbicide checks to make sure herbicides performed well. If not, you have an opportunity to correct the problem with a re-spray.
If you haven't booked a custom applicator to spray fungicide or picked up your fungicide you may almost be out of luck. Book now if you haven't!
The best time to scout for seed drill issues is at the beginning of canola flowering. You can pick out the patterns easily and make adjustments before next year.
With the potential for southerly winds we may see stripe rust show up in the next few weeks.
Cabbage seedpod weevils have climbed above threshold levels in the Standard, AB and south areas. Start sweeping your canola fields.
If your leaves are healthy and green, good, spray a fungicide this year to keep them that way. High humidity and wet weather will spread diseases quickly.

CTF tour Wednesday, July 11th, 1:00 pm

We are hosting a field day with CTF Alberta Thursday, July 11th from 1pm - 4pm at our farm NW of Morrin, AB. Please join us!

When: 1:00 PM to 4:00 PM
Where: One mile west of Morrin, AB on HWY 27 and 1.5 miles north on RR 20-4 (N 51 40.234 and W 112 47.543) Google map

What:
1:00pm – Sign in
1:30pm – Introductions and CTFA project
1:45pm – Steve Larocque, update on 4th year CTF
2:30pm – Nitrogen side dress toolbar (FAST 8100 toolbar)
2:45pm – Crop walk and UAV demo flight (JZ Aerial)
4:00pm – Wrap-up discussion (plant growth regulators, split app nitrogen)

There is no charge for the event. Refreshments will be provided. Three Soil & Water CEUs.

Check the CTFA web site for additional tours July 4th at Dapp.

How hot is too hot for fungicide applications?

Stay within ideal conditions using the Delta T method.

With the recent high temperatures coinciding with fungicide applications, most producers will shut down when temperatures reach 26 degrees Celsius to avoid high evaporation losses. That seems to be the rule of thumb that we all live by and don't question. Unfortunately, temperature is just one half of the equation when it comes to determining evaporation losses. In Australia, where they frequently spray in hot temperatures, they use a measure called Delta T to determine when to shut down spraying to avoid evaporation losses. The equation includes humidity and temperature to determine the lifetime of a droplet on a leaf.

Delta T is the standard indicator for acceptable spray conditions in Australia. It is indicative of evaporation rate and droplet lifetime. Delta T is calculated by subtracting the wet bulb temperature from the dry bulb temperature. The diagram shown here relates air temperature and relative humidity to values of Delta T. As temperature increases, spraying conditions deteriorate unless humidity also increases. When applying pesticides, Delta T should ideally be between 2 and 8.

I can't find dry bulb information but I did find wet bulb data on my Weatherbug weather station. However, based on the chart above we only need air temperature and relative humidity to come up with the appropriate Delta T value. For example, the daytime temperature has reached 28-30 degrees Celsius the last few days with a relative humidity in 60's and 70's. We would normally stop spraying at 26 degrees Celsius regardless of humidity levels but based on the Delta T values, we'd still be in the preferred range. We could have got a lot more spraying done in the last few days had we relied on an suitable measure of evaporation like the Delta T method offers.

I think most of us pay attention to temperature and wind speed when it comes to applying pesticides. Very few if any pay attention to humidity. I think the Delta T model is a more accurate tool to determine evaporation rates and allow us to spray during the optimum time of day and even beyond the rule of thumb we follow now. I can see the Delta T method improving the timing of foliar nutrients, herbicides and fungicides. With herbicides and fungicides costing most producers upwards of $40 and acre each year, it's time we look at how to get the most of those dollars. The Delta T method might be one more tool to help us achieve better efficacy in our pesticide applications. SL

Source and Delta T graph

Bloom staging in canola

To help you time your fungicide application properly, here is a simple guide to stage flowering in canola.

Count the open flowers on the main stem including the aborted flowers and newly formed pods.
It generally takes 2 to 4 days for the main stem to move from first flower to 10% bloom.
10% bloom has 10 open flowers on the main stem.
20% bloom has 14 to 16 flowers on the main stem.
30% bloom has 20 flowers on the main stem. Six to eight days after the start of flowering.
50% bloom has more than 20 flowers on the main stem.
Flowers open from the bottom to top on the main stem at a rate of 3 to 5 flowers per day for 14 to 21 days.
Bloom stage can progress at a rate of 3 to 5 % per day. Faster under warm conditions.

Photo: Canola in 15% bloom. S. Larocque

Steve's tips for monitoring insects on canola

Do not spray for cabbage seedpod weevils past 30% bloom. Why? Because the path to destruction has already been laid. Spraying should have happened between 10% to 20% bloom, which is the time weevils deposit their eggs inside the developing pods. Damage occurs in August when weevil larvae eat seeds then leave exit holes that cause premature shattering.
When spraying for lygus bugs remember the economic threshold of 2 lygus per sweep begins at the end of flowering and not before.
Sweep inside the field and away from the headlands. Insect counts are always highest along the headlands where insects like lygus and weevils land first. I check one spot on the headland to see what insects have entered the field and then walk in to do my sweeps.
You cannot count Diamondback Moth, Bertha Armyworm or Beet Webworms thresholds using a sweep net. Count these insects by the square metre or square foot and multiply by 10. SL

Maximizing fungicide efficacy in canola

Spray when the maximum numbers of flowers are open, but prior to significant pod formation and petal drop. Decaying petals provide the initial food source for spores, and carry those spores down into the crop canopy.
Use higher water volumes (10-15 gal/ac) and higher pressures up to 80 psi to cover petals effectively.
Don't overestimate bloom stage in stands with uneven maturity, as a significant number of plants hidden in the canopy may not have completed bolting. Take a walk inside the field to see how many plants are about to begin flowering then refer to my canola growth stage list above.
If conditions have been drier and less conducive to infection, it may be all right to delay a single fungicide application to target an average of 30% bloom. However, if conditions have been wet and odds of significant infection are high, it will be those early infections from the initial petal drop that are likely to do the most damage. Spraying a little early is probably wise.
Consider split applications, especially in fields with uneven maturity, which will lengthen out the bloom period substantially. Split applications should be made at 20% bloom, followed by the second application at around 50% bloom if conditions are still conducive to sclerotinia infection.

Registered fungicides for control of sclerotinia

Astound: 314g per acre
Lance: 142g per acre
Proline: 127ml per acre
Quadris: 404ml per acre
Rovral RX: 850ml per acre
Vertisan: 500ml per acre

Source: Canola Council of Canada

Canola insect thresholds

Beet Webworm: 2 per ft2
Bertha Armyworm: 2 per ft2
Cabbage Seedpod Weevil: 2 per sweep
Diamondback Moth: early flower: 1.5 per plant
Diamondback Moth: mid to late flowering: 2 to 3 per plant
Lygus Bugs: 2 per sweep

For more information on identification and control of canola insect pests see the Canola Council of Canada web site.

Poor drainage killing barley yields

Is compaction costing you?

Everywhere I drive there are pale yellow barley fields stressed out from the 8-10 inches of rain we’ve received since planting. Barley is especially sensitive to low oxygen environments caused by saturated soil. Quenten Knight from Precision Agronomics in Western Australia sent me an interesting photo recently showing the effects of compaction on barley in CTF. The photo on top shows the pale yellow barley in the tramlines after 12 inches of rain in sandy soil. The photo on the bottom is barley field near my place after 8 inches of rain on heavy clay soil.

Soil compaction is an issue in Western Canada and is the root cause of poor drainage in many areas across all soil types. Notice the healthy green barley crop between the tramlines in the top photo. Removing soil compaction and subsequent water logging can mean the difference between an excellent barley crop and a poor one. In fact, in our CTF Alberta project the greatest response occured last year in barley at a 10% yield increase after just one year in CTF. Once again the spring was wet, soils were water logged and the CTF plots allowed water to infiltrate quickly and allow the barley to thrive.

After just two years of CTF in our cooperator plots we’ve tripled water infiltration rates. Keeping excessive water away from the root zone is a key benefit of CTF. CTF helps reduce denitrification, increase nutrient absorption, reduce stress, increase soil carbon dioxide and oxygen so plants and soil biology can thrive. All this from removing random wheel traffic and moving to CTF. Wet/dry and freeze/thaw cycles will repair soil compaction quickly but only if you stop driving over the soil and allowing it time to repair. I’ll leave you with this. Take a look at the photo above and the yellow barley growing in the tramlines. Look at the healthy green barley growing in between the tramlines. The only difference between the two is wheel traffic. CTF pays. SL

Photo source: (top) Quenten Knight, (bottom) Steve Larocque