Agronomist Notes

I’ve finished up my cereal disease checks and have moved on to sclerotinia assessment and control. Disease patterns are quite sporadic this year and the weakness in some varieties has shown. The CDC Go wheat variety has great yield potential but seems to have more tan spot and septoria compared to a variety like AC Harvest. In the barley class, I’ve noticed the newer variety Conlon has a higher incidence of spot blotch and net blotch compared to Xena or Metcalf.

Weather-wise this week has been warm with temperatures in the low to mid 20’s with high humidity and periodic showers, a perfect combination in dense crop canopies for sclerotinia development. Of all the agronomic decisions I make, spraying for sclerotinia is the toughest. My philosophy has never been to spray because the price of canola is high. I also don’t want to risk losing $60 an acre to save $24. There’s been plenty of talk about hot and dry weather but the 10-day forecast calls for more of what we’ve been experiencing. Will that make my job easier?

On the insect front, I’ve found very few insects in my first canola checks from Calgary to Drumheller and Three Hills. There are a few cabbage seedpod weevils around but I’ve heard the greatest numbers are south of Calgary and near Lethbridge where they’ve already sprayed infested fields.

This week we’ll look at canola flowering development and bloom stage identification to help with spray timing. I’ll do the math on sclerotinia losses and what kind of infection warrants a fungicide application. I’ve included information on sclerotinia management and maximizing fungicide efficacy if you do have to spray. We’ll also look briefly at canola insect thresholds and the newest pest in our area, the Orange Blossom Wheat Midge. Lastly, international crop weather and conditions will conclude Market News. 

Crop Staging Area (Calgary to Drumheller to Three Hills)

 

Date Seeded:	April 23-31	May 1-7	May 8-15
Wheat	Heads emerged	Heads emerging	Flag leaf
Canola	70% bloom	50% bloom	25% bloom
Barley	Heads emerged	Heads emerged
Peas	Flowering	Flowering	Early flower

 

This Week in Scouting

Finish cereal leaf disease checks.
Continue sclerotinia risk assessment in canola.
Continue sweeping canola for lygus bugs and seedpod weevils.

One more thing- check into fertilizer prices for pre-ordering. Sounds crazy early but dealers are asking us already.

Agronomy

Canola Development: Flowering to Ripening

To provide a refresher and help you understand canola development a little better, I’ve put together a list of how canola develops from the onset of flowering.

1. Flowering stage begins when the main stem has reaches 30% to 60% of its maximum length.
2. 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.
3. Flowers begin opening on secondary branches 2 to 3 days after the main stem.
4. Flowers are ready for pollination (by wind and insects) up to 3 days after opening.
5. Fertilization occurs within 24 hours after pollination upon which flowers will close and petals will drop.
6. Young pods are visible one day after petals drop.
7. Leaves begin to drop off (senesce) from the bottom upward.
8. Canola seeds begin to develop once the petals drop from the last flower on the main stem.
9. The seed coat expands until the seed is almost full size within the first few weeks of seed development.
10. Seed fill is complete 35 to 45 days after flower opening.
11. Seeds in the lower pods are ripe 40 to 60 days after the first flower.

Bloom Staging in Canola

1. Count the open flowers on the main stem including the aborted flowers and newly formed pods.
2. It generally takes 2 to 4 days for the main stem to move from first flower to 10% bloom.
3. 10% bloom has 10 open flowers on the main stem.
4. 20% bloom has 14 to 16 flowers on the main stem.
5. 30% bloom has 20 flowers on the main stem. Six to eight days after the start of flowering.
6. 50% bloom has more than 20 flowers on the main stem.

Estimating Yield Loss from Sclerotinia

The equation is simple for calculating yield loss from sclerotinia. The rule of thumb is a 50% yield loss in affected areas. For example, if 10% of the field is infected with sclerotinia then you will have a 5% yield loss. If 20% of the field is infected with sclerotinia then you will have a 10% yield loss. However, the loss is dependent on when the infection occurs. For example, a late infection may cause plants to prematurely ripen, but seed fill will occur and a small amount of seed size may be lost.

Steve’s Quick Math: At $30.00 an acre including application costs ($22.00 + $8.00), a 40 bu/ac yield potential and $13.00/bu canola, the breakeven yield loss would be:

Yield loss: $30.00/ac ÷ $13.00/bu = 2.3 bu/acre ÷ 40 bu/ac × 100 = 5.76%
Percentage of infection to breakeven: 5.76% ÷ 50% yield loss = 11.53%

Therefore, in this example we will need to see about a 12% level of infection per field to break even on our fungicide investment. In reality, we should increase that number to something like 15 to 20% infection in order to generate an actual return on the investment. We don’t spend money just to break even. SL

Sclerotinia Stem Rot Management

Timing of fungicide application is critical. Scout for conditions conducive for disease during the early flowering stage and apply a foliar fungicide between 20-50% bloom, with optimum timing at 30% bloom. Once sclerotinia symptoms are present in a crop, foliar fungicides will not be effective. Some fungicides are registered for split applications, providing longer protection during periods of extended bloom under cool wet conditions.
Source: Saskatchewan Agriculture & Food

The link below is a PDF version of the “Canola Disease Identification and Sclerotinia Risk Assessment Card” and can assist growers and crop scouts with spraying decisions.
Link: http://www.canola-councildemo.org/pdf/canola_plant_disease_risk.pdf

What to ask before deciding to spray a fungicide:

1. How heavy is the crop canopy?
2. Has there been excessive moisture prior to flowering?
3. Do they predict rain in the near future?
4. Have your canola rotations been less than 4 years apart?
5. Was there disease incidence in the past?
6. Are there apothecia in neighboring fields where canola was grown last year?
7. Also consider, target yield, fertility program and expected value of canola.

Registered Fungicides for control of Sclerotinia

Lance: Rate: 142g per acre
Proline: Rate: 128ml to 170ml per acre
Quadris: Rate: 200ml to 400ml per acre
Ronilan EG: Rate: 300g to 400g per acre
Rovral Flo: Rate: 850ml to 1250ml per acre

Maximizing Fungicide Efficacy

1. 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.
2. Use higher water volumes and appropriate nozzles to ensure good spray coverage. This is especially important in crops with very dense canopies.
3. 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. If more mature plants are starting to drop petals, take into consideration the weather conditions.
4. 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.
5. Consider split applications, especially in fields with uneven maturity, which will lengthen out the bloom period substantially. For most products registered for split application it is recommended to make the initial application at about 20% bloom, followed by the second application at around 50% bloom if conditions are still conducive to sclerotinia infection.

Source: Canola Council of Canada

Wheat Midge Identification, Damage & Control

These small bugs are about half the size of a mosquito and bright orange. They lay eggs in the wheat head and the larvae will then feed on the wheat kernels.

Damage Potential

One midge per 4-5 wheat heads can decrease yield around 15 percent. They can also reduce the grade of your wheat. If there is more than one midge per 8-10 wheat heads there is a risk of a reduced grade. The Canadian Grain Commission limits midge damage in No. 1 CWRS wheat to 2% and 8% in No.2. In durum the tolerances are similar.

Scouting

Adults appear in late June and early July. Wheat fields should be scouted regularly between heading and flowering. Scout in the evenings, from about 8 - 10 pm, when the temperature is around 15 degrees Celsius and there is no or very light winds. Also, scout four or five places in the field for a more accurate count.

Threshold

One adult midge per four or five wheat heads is usually enough to warrant control measures.

Control

Cygon™, Lagon™, Lorsban 4E™, Nufos™ and Pyrinex™ are all registered for use on wheat midge in wheat. Check the label for any other restrictions regarding the chemicals. For example Cygon™ and Lagon™ do not control the eggs, just the adults. Also, watch the stage of the crop, as certain chemicals have to be applied at specific times for good control. Check the label for application timing.

Considerations for Control

Late evening or early morning are the best times to control the adults, as the females are most active in cool nighttime temperatures (but above 15 degrees Celsius or 59 degrees Fahrenheit) and when the wind is less than 10 km/hr (6 mph). Also, good coverage is critical for control if your chemical controls eggs as well, so make sure your water volume is adequate. Optimal control happens when 70% of the crop is in the heading to flower stage. If 30-60% of the crop is flowering then it needs to be sprayed immediately to have good control on the wheat midge. If 80% of the crop is flowering then control is not recommended as the window has passed and the midge damage has already started. Spraying therefore should be done early to protect the main stem and first tiller, as this is where most of the yield potential of the crop is.

Wheat Midge Forecast Maps

Midge emergence can be modeled using accumulated temperature calculations called Growing Degree Day (GDD). Data provided by Agriculture & AgriFood Canada (AAFC), Saskatoon suggest using a base temperature of 5°C for predicting midge emergence patterns using accumulated GDDs. Thresholds for combined emergence of male and female midge are:
10% emergence     693 (±39) GDD
50% emergence     784 (±38) GDD
90% emergence     874 (±41) GDD

As of July 4th in the Calgary corridor we are at 568 GDD.

Wheat Midge Information: http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex2507?opendocument
Alberta Midge Forecast map: http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/prm11907/$FILE/08wheatmidgeab.jpg
Prairie Midge Emergence maps: http://www.cwb.ca/public/en/farmers/weather/midge/

Cabbage Seedpod Weevil – Update on Timing

The economic threshold for the weevil has been lowered to 2 weevils per sweep. It is important not to spray too soon, as the weevil will typically continue to invade for at least a week to 10 days beyond the opening of the first flowers. The optimum time to spray for cabbage seedpod weevil is early flowering, or more specifically, when 70% of plants have 3-10 open flowers. Spraying at this stage will allow the weevils more time to move into the field, but it is still early enough to keep them from laying a significant number of eggs in newly forming pods while helping to protect beneficial insects, including pollinators, which have moved into the field.
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: 1.5 to 2 per sweep

For more information on identification and control of canola insect pests:
http://www.canola-council.org/chapter10b.aspx#ch10b_sec7

Market News

International Crop and Weather Highlights

Europe: In northeastern Europe, showers further improve moisture supplies for filling winter wheat. In central Europe, wet weather benefits filling winter grains and vegetative summer crops. Dry, increasingly hot weather in southern Europe favors winter grain maturation and early harvesting. Yield prospects are good for 2008.

Former Soviet Union: In Ukraine, warm, dry weather favors early winter grain harvesting and spring-sown crop development. In Russia, showers and thunderstorms favor immature winter grains and spring-sown crops in the west, while recent showers boost soil moisture for spring wheat development in the east. In Kazakhstan, recent showers and cooler weather improve growing conditions for spring grains. Crop conditions for spring and winter crops are good to excellent.

East Asia: Light showers maintain favorable soil moisture for vegetative corn and soybeans in Manchuria. Wheat conditions are very good.

Southest Asia: Monsoon showers soak corn areas in the Philippines.

South Asia: Locally heavy rain in northern India slows the recession of flood waters and hampers planting of soybeans. Continuing heavy showers maintain flooding for soybeans in central India.

Australia: Dry weather follows last week’s beneficial rainfall in New South Wales, allowing additional winter wheat and barley planting but providing no additional drought relief. Elsewhere in southern and eastern Australia, dry weather reduces soil moisture for winter grains. In Western Australia, widespread showers help winter grain establishment.

South America: Wheat planting progresses in La Pampa and Buenos Aires, after last week’s rain. However, drought is reportedly hindering planting in other major Argentine growing areas of Cordoba and Santa Fe. Rain continues in the main wheat areas of southern Brazil.

Canada: Showers and seasonably mild weather benefit vegetative spring grains and oilseeds in most Prairie growing areas.

Mexico: Scattered showers benefit some southern crop areas, but dry pockets linger in corn areas of the southern plateau.

United States: In the West, dry, warmer-than-normal weather continues throughout most major farming areas. On the Plains, rain is gradually diminishing on northern High Plains as scattered showers and thunderstorms form on the central and southern High Plains. The rain in the south is bringing localized relief to drought-stressed summer crops but winter wheat harvesting is likely experiencing some delays. In the Corn Belt, locally heavy showers continue from Missouri to the eastern Great Lakes Region, causing additional flooding of low-lying farmland. Drier weather, albeit cool, is bringing some relief from wetness to the upper Midwest. In the South, heat and dryness further stress rain-fed summer row crops from the southern Plains to the southern Atlantic Coast.