Beyond Agronomy News: July 22nd, 2008

Agronomy

This Week in Scouting

• Continue scouting for wheat midge from late-boot to early-flowering.
• Continue scouting for canola insects.
• Re-evaluate wild oat control in fields with history of heavy wild oat pressure.

Wheat Midge Update: Stick to Thresholds

The planes are flying around us yet my clients and I can't seem to find wheat midge above threshold. The most I've counted is one midge per 20 heads. Thankfully, most of the wheat I manage is now flowering or finished flowering, which is past the point of concern.

Wheat plants have a natural control mechanism called ferulic acid. The development of this toxic compound begins at flowering and will kill midge larvae that have hatched inside the developing kernel. Another natural control mechanism is the buildup of natural predators at the time of flowering. The numbers of natural predators like parasitic wasps tends to coincide with start of flowering. Unfortunately, those who are spraying for "revenge" will only wipe out the beneficial insects and not provide the control they're looking for. This will only serve to increase levels of midge next year as their natural enemies have been destroyed.

Tips to remember about wheat midge:
One midge per 4 heads can reduce yield by 7.5%.
Scout fields from late boot until early flowering.
Scout fields from 9:00pm until 10:30pm with temperatures above 15 degrees Celsius.
Threshold is 1 midge per 8 heads to protect grade.
Threshold is 1 midge per 4 heads to protect yield.
Wait three days after midge threshold has been reached to apply an insecticide.
Flowering (anthesis) starts in the middle of the head and progresses outwards.
Flowering takes approximately 3 to 4 days to finish and 7 to 10 days in cooler weather.
Cost of control is approximately $16 an acre including application. SL

Photo source: UAP

Predict Harvest Using Growing Degree Days

It's the last week of a cool and wet July and I wonder, how long until harvest? Predicting harvest dates by the calendar is very misleading. Using growing degree-days provides you with a more accurate measure for harvest timing.

All plant functions, such as evapotranspiration, photosynthesis, water and nutrient absorption and transport, enzyme activity, and other biological and chemical activities are regulated by temperature. For this reason, the development of the crop is more closely related to the amount of heat the crop is exposed to than calendar days. Other factors such as moisture, light (day length), nutrition and variety also play a role, but they generally have less influence.

Canola requires 1,432 to 1,557 growing degree-days (GDD's) to reach an optimum swathing stage of 40% seed colour change. Hard red spring wheat is similar to canola and requires 1,538 to 1,665 GDD's to reach maturity. Barley needs 1,269 to 1,522 GDD's. Surprisingly, peas need 1,527 to 1,686 GDD's to reach 90% seed colour change.

Let's do the math for wheat, barley and canola seeded near Three Hills, AB, on May 1st. The climate data provided on farmzone.com shows we've received 783 GDD's since May 1st. The average over the last 10 days has been 12 GDD per day, which is 10 GDD cooler than normal for this time of year. To calculate the predicted harvest date for our crops this fall, we'll add a few more GDD to compensate for the typically warmer, late July-August period to an estimated 15 GDD per day. At this time last year, our GDD's were 26 per day.

Let's finish the math:
Canola: 1,432 - 783 ÷ 15 = 43 days until swathing or September 2
Wheat: 1,538 - 783 ÷ 15 = 50 days until maturity or September 9
Barley: 1,269 - 783 ÷ 15 = 32 days until maturity or August 22

So there you have it. I would encourage you to keep track of growing degree-days to help you estimate swath and harvest timing this fall. Perhaps a pre-harvest glyphosate drydown may be in order if the cool weather continues. SL

Check out farmzone.com. Find your area and click on "Historical" data.

Show and Tell: Herbicide Stunts and Accelerates Maturity

This week, I stumbled on an interesting field of Cowboy barley while looking at hail damage in an adjacent canola crop. The considerate neighbors did not spray the barley headlands for fear of drifting herbicide on to the Liberty Link canola. The difference in plant height and color was very dramatic! After further inspection, I noticed the unsprayed headland was roughly 10 days less mature and 6 inches taller than the rest of the field.

The field was sprayed with Achieve Liquid Gold in the evening followed by a cool night. I've seen this effect in wheat and barley with both Horizon and Achieve Liquid Gold when tank mixed with herbicides containing bromoxynil, such as Buctril M. Some producers have also witnessed reduction in plant height with Infinity, the new broadleaf herbicide by Bayer CropScience. It too has bromoxynil as one of the components.

The best way to avoid this hazard is to be cognizant of the nighttime temperatures that follow application. If temperatures drop below 10 degrees Celsius, you should avoid spraying products containing bromoxynil, including Buctril M, Infinity, Thumper and Unity. Secondly, be sure plants have reached the 4-leaf, 2-tiller stage. In my experience, the most susceptible stage seems to be at 4-leaf or 4-leaf, 1-tiller and earlier. SL

Integrated Crop Management School Highlights

Here are the highlights of what I learned at the field school at Olds, AB, last week:

Herbicides Module

• The day after an application of Liberty herbicide is just as important as the day you spray. Warm and sunny weather the day following a Liberty application will dramatically improve control.
• Spraying Liberty in the evening is fine so long as the temperature is warm enough during application and the following day is sunny and warm. Cloudy conditions following application reduces efficacy.
• Only 10 to 15% of Group 1 wild oat herbicides actually translocate within the plant. Most Group 1's rely on spray droplets to move down the leaf to the growing point. That is one of the reasons water volumes are important when dealing with heavy wild oat populations.
• Many custom applicators mentioned that they've had success controlling white cockle with Spectrum.
• To improve the efficacy of the new broadleaf herbicide, Infinity, on perennials, cleavers and chickweed, you must add ammonium sulphate. Ammonium sulphate improves uptake into the plant; not through the pH adjustment that comes with adding it.

Pulse Agronomy Module

• he red colour inside the pea nodule is caused by leg-hemoglobin. The red colour indicates that rhizobium bacteria that fix nitrogen have oxygen and are alive.
• Peas can nodulate from naturally occurring rhizobium in the soil. Just because peas have nodules, doesn't mean the bacteria inside are alive.
• Peas begin to slough off their nodules at the start of flowering.
• When seeding into a soil with a pH of 5.5 or less, use clay-based inoculants to help buffer the pH and help the bacteria to survive and multiply.
• To control annual sowthistle in peas, use a later application of Basagran.

Insects and Disease Modules

• Scouting for cabbage seedpod weevils must begin at bolting and finish up by 30% bloom. If thresholds are high at 30% bloom than you've already missed the optimum timing for control at early bloom. Weevils chew holes in pods that are 1 inch long and insert their eggs.
• The over use of fungicides in canola can significantly impact the beneficial insects that control root maggots. The fungicides used in canola control the fungi that root maggots need to survive.
• A small amount of lygus bugs in your canola can actually stimulate pollination and increase yield.

Malt Barley Agronomy Module

• Higher malt barley seeding rates targeted at 30 plants per square foot decreases plumpness somewhat but increases malt quality dramatically through more uniform kernel size. Uniform kernel size adds more profitability to maltsters than plumpness. SL

Market News

International Crop and Weather Highlights

United States: In the West, seasonal showers continue to spread northward. Elsewhere, cooler weather prevails in California, while hot, dry weather in the Northwest favors winter wheat maturation but is maintaining stress on spring-sown small grains. On the Plains, hot, mostly dry weather favors winter wheat harvesting across the northern half of the region. However, heat is also stressing summer crops, especially in areas with inadequate soil moisture. In the Corn Belt, strong thunderstorms are sweeping through the upper Mississippi Valley, maintaining soggy conditions in Iowa and neighboring areas. In the Ohio Valley, however, a marked short-term drying trend is promoting winter wheat harvesting and rapid summer crop maturation.

Europe: In central and northern Europe, showers provide favorable moisture supplies for filling spring wheat and vegetative summer crops. However, the rain slows winter crop maturation and early harvesting. In the Balkans, dry weather favors winter crop harvesting but reduces soil moisture for reproductive corn and sunflowers.

Former Soviet Union: In western Russia, drier weather helps winter wheat harvesting in the Southern District, while variable showers maintain favorable moisture for spring-sown crops in the Central and Volga Districts. In Ukraine, showers ease short-term dryness in southern and eastern areas, improving growing conditions for spring-sown crops but slowing winter grain harvesting. Increasing heat and dryness follow in the wake of last week's beneficial rain across key spring wheat producing areas of north-central Kazakhstan and the Urals District in Russia.

East Asia: Widespread showers and warm weather favor summer crops throughout the East.

Southeast Asia: Monsoon showers maintain favorable soil moisture for corn in Thailand. Drier weather in the Philippines eases wetness in southern and central growing areas.

South Asia: Locally heavy rain in central and northern portions of Pakistan and India maintains adequate to abundant soil moisture for emerging to vegetative summer crops.

Australia: In South Australia, Victoria, and New South Wales, widespread, soaking rains provide a needed boost in topsoil moisture, helping winter grain germination, emergence, and establishment. In Western Australia and Queensland, light showers benefit vegetative winter grains.

South America: Light rain boosts topsoil moisture for germination in key winter grain areas of central Argentina, but dry pockets continue, and much more rainfall is needed to significantly improve planting prospects. Showers maintain generally favorable conditions for winter wheat in Rio Grande do Sul, Brazil, but drier weather is raising concern elsewhere.

Canada: Conditions are mostly favorable for vegetative to reproductive spring grains and oilseeds./p>

Mexico: Locally heavy showers continue across the southern plateau corn belt. Unseasonably heavy rain falls in northern watersheds./p>