June 18, 2013

Agronomist Notes

Hello Reader

Oh, look at that, more rain. The cooler, wet weather we had last week will likely continue for the next 14 days. Crop progress is starting to fall behind the norm, which has given us some breathing room on herbicide timing. Spray windows have been tight between wind and rain.

Many producers have been eager to try top dressing nitrogen this year with the heavy, early rains and the potential for higher yields. I’m now into post herbicide scouting and the results have been excellent so far. Warm(ish) overnight temperatures and high humidity levels have been very helpful.

This week we’ll look at herbicide symptoms to help with your post-herbicide checks. Next, we’ll take a look at look at this years weather data to see how the season is shaping up. Last we’ll look at a residual herbicides and how to avoid crop injury. We’ll finish with technical grain market news.

Pictured above: Starland Colony streaming liquid nitrogen on to barley, near Morrin, AB.

Crop Staging

(Calgary to Drumheller to Three Hills)

Seeded May 1-7 May 8-15 May 15-22
Wheat 1st node 5-leaf 2 tiller 4-leaf 1 tiller
Canola 6-leaf 4-leaf 3-leaf
Barley 1st node 5-leaf 2 tiller 4-leaf 1 tiller
Peas 12th node 10th node 7th node

Steve's tips & tricks of the week

Follow me on Twitter for in-season updates @BeyondAgronomy

It’s time to begin post-herbicide checks to make sure herbicides performed well. If not, you have an opportunity to correct the problem with a re-spray.
Watch for cold (5C or less) overnight temperatures during spraying. Spraying in the evening followed by cold overnight temperatures can stress wheat and barley and reduce herbicide efficacy.
Early seeded wheat is nearing the start of stem elongation so prepare to top dress nitrogen by the end of the week.
Stripe rust is now in Washington State and Southern Idaho. With the potential for southerly winds we may see stripe rust show up early this year.
Early leaf diseases are showing up in wheat and barley. If you plan on adding a fungicide with your herbicide, save the application timing to late tillering if possible. The leaves you’re protecting at 2-3 leaf stage die off at canopy closure and contribute little to yield.

It's Time to Check Post-Herbicide Efficacies

The most important role of a farmer or crop advisor during spray season is not only to apply the correct herbicides at the right time but to follow up with post herbicide checks. Follow up efficacy checks should be done 10 to 14 days after application. More wild oat or weed escapes can be corrected if only producers and professionals checked how well the herbicides worked after application. Calling the chemical representatives at harvest to tell them the herbicide didn't work is futile and besides, herbicide inquiry cut off dates are usually around the 15th of July.

Below is a list of herbicide injury symptoms for the top six herbicide groups I use to help identify herbicide injury and efficacy.

Group 1. ACCase: Axial, Achieve Liquid, Horizon, Puma Advance, Centurion
Symptoms: The first sign of injury on wild oats or green foxtail may appear as intervenal chlorosis or yellow striping on newer leaves. Older leaves may show red or purple. The growing point turns brown and dies. The newest leaf can be easily pulled from the crown where you will see a "pinching" at the base of the leaf. New growth dies first, such that the plant appears to take considerable time to die after application.

Group 2. ALS: Simplicity, Everest, Frontline XL, Refine SG, Odyssey, Varro
Symptoms: In broadleaf weeds the first visible symptom is the termination of plant growth. A few days after application you may see yellowing, reddening and purpling of the leaves. In grassy weeds like wild oats, you may see a yellow striping and purplish discoloration of the leaves. The youngest leaves die first followed by older leaves. Death of grassy weeds may take 1 to 3 weeks to occur.

Group 4. Auxinic: 2,4-D, MCPA, Attain, Buctril M, Curtail M, Frontline XL, Target
Symptoms: Bending and twisting of stems and petioles, stem swelling, especially at the nodes, elongation, leaf cupping and leaf curling. These signs are followed by yellowing at the growing point, growth inhibition and wilting.

Group 6. Photosynthetic Inhibitors: Buctril M, Infinity, Benchmark, Thumper
Symptoms: Rapid yellowing and whitening begins at the leaf edges. Later symptoms include desiccation and a burned-off appearance of the leaves. Symptoms develop rapidly under full sunlight conditions.

Group 9. EPSPS: Glyphosate: Roundup WeatherMax, Touchdown Total, Vantage PlusMax
Symptoms: Gradual wilting and yellowing at the growing point of the plant that advances into browning of above ground growth. Annuals may show signs within 2-4 days and perennials within 7-10 days.

Group 10. Glutamine Synthetase Inhibitor: Liberty 150
Symptoms: Yellowing and wilting usually occur within one to three days after application, followed by necrosis or bleaching-death of plant tissue. Symptoms develop more rapidly under bright sunlight, high humidity and moist soil.

Group 27. HPPD Inhibitors: Infinity, Tundra, Velocity
Symptoms: Small burnt spots on the broadleaf weeds can appear within hours. The pigment and photosynthesis of the plant shuts down resulting in bleaching symptoms with 6 to 14 days.

Here is a link to the visual symptoms of each herbicide Group:

Reference: How Herbicides Work, Alberta Ag publication

Growing Degree Days

A look at this year's vintage

The late start and cooler weather this spring has given the impression that crop maturity is behind, but by how much? Crop maturity is directly affected by the number of growing degree days we receive each year. Growing degree days is simply the calculation of the highest daily temperature plus the lowest daily temperature divided by two and subtracting five (Ex: 200C + 100C ÷ 2 - 5 = 10 GGD). Five is subtracted because it is assumed that plant growth does not occur at less than five degrees Celsius. We are currently at 406 GDDs; here is the historical log:

Growing Degree Days from May 1st to June 16th:
2013: 406 (Rain 124.5 mm)
2012: 365 (Rain 155.8 mm)
2011: 350 (Rain 75.1 mm)
2010: 269 (Rain 108.6 mm)
2009: 316 (Rain 40.3 mm)
2008: 352 (Rain 139.5 mm)
2007: 394 (Rain 125.4 mm)
2006: 449 (Rain 88 mm)
2005: 376 (Rain 59.2 mm)
2004: 320 (Rain 55 mm)
10-year average: 360 GDD’s (Rain 97 mm)

Growing degree days are 18% higher than the ten year average with 29% more rain fall. We’re setting up close to year 2007, which was a cool, wet year with feed quality grains but high yields. The 14-day trend is calling for temperatures in the low 20’s with overnights in the low teens and single digits. We’ll need some serious heat in July-August to avoid fall frosts. Based on the weather data, I’m very optimistic on yield potential but slightly concerned about frost on the other end of the growing season. Time will tell. SL

Avoiding Group 2 residual herbicide injury

Group 2 residual herbicides applied pre or post seeding are becoming a very popular way to control flushing broadleaf weeds like canola, cleavers and wild buckwheat early in the growing season. Products like PrePass (florasulam) and Express Pro (Tribenuron methyl and metsulfuron methyl) are often applied to canola stubble destined for wheat or barley. Unfortunately, many early seeded fields are planted shallow and may be in danger of sitting in the treated herbicide layer.

It is well known that Group 2 herbicides can travel easily through the soil by water. Sandy textured sols, low in organic matter have the greatest potential for leaching herbicide into the furrow when application is followed by heavy rains. In the last two years we’ve seen excessive rains in late May and early June and subsequently an increase in Group 2 damage symptoms like interveinal chlorosis or yellow striping along the leaf veins in new growth.

The photo you see above shows an area where the wheat is stunted and showing signs of Group 2 damage. If you dig the plants up in the affected area you’ll find the seeds planted shallow at about 3/4 of an inch. The unaffected areas are planted at 1 to 1 1/4 inches and lie under the treated layer. This field had 6 inches of rain from May 19th to June 1st and is a heavy clay soil type with poor tilth and low organic matter. Herbicides are less likely to leach in clay soils but with 6 inches of rain, it is still possible.

What normally happens is a crop that comes up nicely and looks excellent, then by the third or fourth leaf stage becomes thin and stunted. In many cases an in-crop herbicide has not been applied yet the symptoms show up in shallow seeded fields, most of them on canola stubble. Coincidentally, most canola fields receive a Group 2 residual herbicide prior to or within a few days after seeding.

The best way to avoid herbicide injury is to plant wheat and barley deeper than 3/4 of an inch and away from the treated layer. It’s no different than applying Avadex or Treflan where you incorporate the herbicide and plant below the treated layer so the roots don’t take up the herbicide. Shallow seeding is very common in late April and early May and could be putting many at risk for Group2 herbicide injury. SL