Ontario Field Crop Report
May 28, 2008
by OMAFRA Field Crop Specialists

For emerging issues, questions or to provide feedback on this report, contact the CropLine at 1-888-449-0937.  Technical information can also be obtained at the OMAFRA Field Crops Webpage at www.ontario.ca/crops and Crop Pest Ontario at www.omafra.gov.on.ca/croppest/.  Referenced OMAFRA Publications include Publication 811 Agronomy Guide for Field Crops ($20), 812 Field Crop Protection Guide ($15), 75 Guide to Weed Control ($15), and 505 Ontario Weeds ($15).  These can be obtained from your OMAFRA Resource Centre, or by calling 1-800-668-9938.

Winter Cereals
Frost was widespread across much of south western Ontario on Wednesday morning (May 28th), with many reports of -2°C.  There is concern over damage to winter wheat and winter barley crops.  Winter barley is especially critical as it has headed out and is pollinating or just in embryo development.  Early winter wheat is also at risk, as it is very close to beginning meiosis for pollination.  The impact of the frost is currently being assessed.

Assessing damage requires examining the florets (head), particularly the anthers.  Healthy anthers are light yellow-green and turgid.  Damaged anthers will loose their turgidity, become twisted and shrivelled, with the colour eventually changing to white-grey.  It takes 24-48 hours for these symptoms to appear.  Yield impact can be severe under worst case scenarios.  See http://wheat.colostate.edu/freeze.pdf.  Although, unlikely, if severe damage is evident growers may consider harvesting as silage and replanting to edible beans.  Edible bean contracts and seed are still available.

The early winter wheat in Essex County is now headed out.  These fields are approaching the stage for fusarium control.  For fusarium head blight control, Folicur or Proline should be applied from day two to day four (day zero equals 75% heads fully emerged).  See http://www.weatherinnovations.com/fusariumeast.cfm  Sprayer tank and end cap cleanout is essential if fungicides will be applied to wheat at fusarium timing.  Wheat is incredibly sensitive to herbicide injury at this stage.  Be sure to follow proper tank cleanout, including use of the proper tank cleaner, and remove ALL end caps while flushing the boom.

Aphid pressure is low, with isolated fields in the southwest at 8-10 aphids per stem.  The threshold for control is 15 aphids/stem prior to heading, 50 aphids/head after heading.  However, with warmer temperatures, predators will become more numerous and active.  Scout and consider control, but do not spray too early, to give natural predators a chance.

Spring Cereals
Most are in the tillering stage (Growth Stage (GS) 21-26) and herbicides should already have been applied.  Fields at the first node (GS 31) are beyond the optimum stage for herbicide application.  Once the crop reaches second node (GS 32), yield loss, due to weed pressure, will not be reduced by a late herbicide application and significant herbicide damage to head formation and pollination may occur. 

Leaf disease pressure remains nearly non-existent in most spring cereals due to the cool weather.  Continue to scout fields for early signs of leaf diseases.  After this period of cool weather, a sudden change to high temperatures and sun burning can cause physiological fleck.  Physiological fleck may be mistakenly identified with leaf disease, but can be distinguished from leaf diseases by putting a few leaves and a drop of water in a sealed plastic bag.  Store at room temperature for 12-24 hours and if the symptoms are leaf diseases, they will develop pycnidia (black pepper spots) rapidly on the leaves.

Soybeans
Warm weather and favourable soil conditions saw a number of soybean acres planted over the past week.  As of May 28th, planted acreage estimates ranged from 50-90% depending on the area and soil conditions.  The majority of planting should be completed by the beginning of June.

Soybeans that were planted during the mid to early part of May have emerged, and are generally in good condition.  Growth stages, of the early planted beans, will range from emergence to the unifoliate stage.  This is a critical scouting window for identifying plant stands and to evaluate the level of weed and other pest management needed.

Soybeans should be kept weed-free from the 1st to 3rd trifoliate stage to minimize yield loses from weeds.  In many instances, this year weed emergence has preceded crop emergence, therefore, weed control may need to be initiated earlier than normal.  Focus on weed stage when considering what herbicide programs to use.  Table 11-5 in OMAFRA Publication 75 lists soybean herbicides, and the maximum weed leaf and crop stages at which they can be applied.

If there are 250,000 plants/ha (100,000 plants/acre), leave the stand!  (100,000 plants/acre = 16 plants in a 91 cm (36 inches) hula hoop, 14 in an 84 cm (33 inches), 11 in a 76 cm (30 inches).  The exception to this rule may be very heavy clay soils.  More plants per acre (10 -15%) are required on heavy clay soils.  Do not change maturity on soybean varieties if replanting now.  Stay with full season soybeans. See the Agronomy Guide (OMAFRA Publication 811) for more details.

Bean leaf beetle are starting to enter emerging soybean fields.  Cruiser seed treatment will control these early infestations, but for untreated fields, scout 10 plants in 5 areas of the field as soon as it emerges.  Spraying is warranted if there are 16 beetles per foot of row (52 per meter of row), or if there is significant clipping of the seedlings.

Seedcorn maggots also love cool, wet weather.  High risk fields are those with cover crops recently plowed under, fields with manure applied or heavy weed pressures just prior to planting, and those fields planted to deep.  Cruiser seed treatment works very well on seedcorn maggots so only those fields not treated with these are at risk.  Any fields requiring replanting should consider planting them with insecticide seed treatment. 

Corn
Early planted corn is in the four leaf stage in many fields.  Corn planted in the early part of May is in the two to three leaf stage while the late planted is one to two leaf.  The corn continues to be very yellow because of the recent cool temperatures.  In general, it has been taking 2.5 to 3 weeks for the crop to emerge.  CHU’s to date in Ontario for the period May 1st to the 26th are London 259, Waterloo 227 and Ottawa 298.

The early planted corn is in the beginning of the critical weed free period.  Although corn growth has been slow, the weeds have been moving along, and in many cases are more mature then what we would expect for the stage of the corn.  Although the critical weed free period in corn is between the 3 and 8-leaf stage, the critical point for any individual field is a function of weed species, density, soil type, soil moisture among others.  It is always advised to apply in the early stages of the period unless weed density is very low. Fields with light textured soils and high weed densities will be most critical for early application.

Be conscious of the cold temperatures and especially the temperature swings that we have been experiencing.  Some herbicides sprayed under these conditions can result in significant injury to corn.

Corn planted into the tougher conditions in early to mid May, has been experiencing some soil crusting.  These fields should be inspected and if the crop is having difficulty emerging because of a crust, consider breaking that crust.  Although the first thought is a rotary hoe, they are often not aggressive enough.  Consider using the drill or corn planter with coulters set very shallow to provide enough weight to break that crust.

If replanting is warranted, avoid tillage as the method for removing the original stand of corn.  Plant immediately to an herbicide tolerant hybrid and use herbicide application to remove the original stand.

Forages
With the extended cool weather, development of alfalfa and grasses is typically a few days behind normal.  Many dairy producers have begun silo filling.  Dairy producers generally target harvesting first-cut alfalfa at about 40% NDF.  Fibre levels can vary widely from year to year when based on calendar dates.  Fibre levels can also vary considerably when based on mid-bud or late-bud stage.  Scissors-cut laboratory analysis, Growing Degree Days (GDD), and “PEAQ stick” (Predictive Equations For Alfalfa Quality) estimates of NDF (www.omafra.gov.on.ca/english/crops/facts/info_ndf.htm) are useful indicators of optimum time of alfalfa first-cut harvest.  The Agri-Food Laboratories website (www.agtest.com) provides a useful tool to predict optimum harvest dates for alfalfa and grasses based on GDD for your area.

Wide swath haylage can achieve short wilting times (haylage-in-a-day) that significantly improves forage quality.  Rapid wilting is critical to minimize the often significant respiration losses of plant sugars.  Adjusting the mower to leave as wide a swath as practical will speed wilting. Wide swath width (85% of cutter-bar width) and sunlight (morning cutting) are the keys to fast wilting for haylage high in digestible energy and improved fermentation.  Wide swaths need to be narrowed for chopping. Milk producers and custom operators using wide swaths are adopting the use of windrow mergers that use a pickup and belt, rather than rakes, in order to reduce the risk of rocks and soil contamination.  Refer to “Wide Swath Haylage” at www.omafra.gov.on.ca/english/crops/facts/w_s_haylage.htm.

Fill, pack, cover and seal bunker silos quickly.  Packing is the weakest link in bunker silo management.  Pack in thin layers of no more than 15 cm (6 inches) in order to get good air exclusion and high silage density.  Take precautions to prevent tractor rollovers. Sufficient tractor weight and packing time is critical.  A high delivery rate to the silo is desired, but this may mean using bigger packing tractors, adding more tractor weight, or more packing tractors in order to increase packing time per ton.

Canola
Planting finished this week in western Ontario, and northern areas are 80% complete.  Frost on the morning of May 28th appears to have caused minimal damage to emerged canola.  Emergence is good on early planted stands and they are in the 1-3 leaf stage.  Keep on top of post emergent herbicide applications.  It takes about 70 growing degree days to develop each new canola leaf, so the crop will advance a new leaf every 4-5 days. Canola should be maintained weed free up to the six-leaf stage for maximum yield potential.  Allowing significant early weed pressure to build in your canola field will result in yield losses.  Trials have shown a 10% yield improvement by spraying at 2-leaf stage versus the 5-leaf stage.  Concentrate on controlling weeds that emerge with the canola, and less on weeds that come up after the 4-6 leaf stage.  If dandelions or other perennials weeds are present, the high rate of glyphosate should be used in RR Canola.  If cool conditions prevail, herbicide activity with Liberty is improved if applied during the heat of the day.

Check fields for flea beetle activity.  Populations and damage has been low to date, but can build quickly under warm (>150°C), sunny weather.  Seed treatments provide protection for 3-4 weeks from time of planting, so in some cases control may have run out before canola is past the critical stage (3-4 leaves).  Action threshold is 25% leaf feeding damage.