Ontario Field Crop Report
June 4, 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.

Corn
Breaking news…May was cool!  Total crop heat unit (CHU) accumulation for May this year was 330, 288, and 371 for London, Waterloo and Ottawa respectively.  In 2007, the totals for May were 480, 429, and 436 CHU.

Much of the corn is at or near the 3-leaf stage (leaf over method).  If weeds have emerged with the crop, weed control now becomes a prime consideration.  If temperatures are near normal, corn will develop about 2-leaf stages in a week.  In fields where weed pressure is significant, delaying post-emerge spraying from the 4-leaf stage to the 6-leaf stage may result in some real yield loss.

Black cutworm activity has started in some corn fields.  Only Herculex varieties or Poncho seed treatment will provide any protection, and only from the younger larvae.  Once the larvae get bigger, these control measures are not as effective.  Look for wilting plants, foliage feeding or plants being cut off at the ground.  Dig around damaged plants and search through the soil, as cutworms like to hide under soil clods during the day.  If 5-10% of plants show leaf feeding injury, foliar rescue treatments at that time are very effective.  Once corn reaches the 5-leaf stage and begins to produce roots at the base of the plant, the risk has passed.  

Sidedressing nitrogen will begin shortly.  Ontario’s recommendation for N rates on corn can be found by going to www.gocorn.net and clicking on the Nitrogen Calculator.  Soil samples, Pre-Sidedress Nitrogen Test (PSNT), can also assist in fine-tuning sidedress N recommendations.  Soil samples need to be taken pre-sidedress and must be taken to a 30 cm (12”) depth.  A laboratory analysis for soil nitrate can then be used to determine an N recommendation.  Refer to pages 65-66, OMAFRA Publication 811, Agronomy Guide.

Soybeans
The majority of soybeans were planted by the end of May, but growth has been slow.  About 5-8% of fields still need to be planted.  Soybeans have the ability to adjust to delays in planting.  A one month delay in planting will generally delay maturity by only nine days.  Do not consider switching to shorter day varieties until after mid June.
-
The majority of fields are emerging well.  However, fields planted from about May 9-11 were challenged by cool, wet weather resulting in some difficulty in emergence.  Late May planted beans are emerging quickly and are generally in excellent condition.  Growth stages range from emergence to the first-trifoliate stage. 

Early season competition from weeds reduces yields.  Soybeans should not go beyond the third-trifoliate before weeds are eliminated.  Although each field is unique, most fields should receive post-emergent sprays within 21-28 days after planting.  Even in glyphosate tolerant fields, weeds must be controlled early to maximize yields.  The first- to third-trifoliate leaf stage is usually optimum for the first in-crop application of glyphosate. 

A number of products should not be applied until soybeans have the first-trifoliate fully expanded.  Applications prior to this stage can result in crop injury.  Once the minimum crop stage is reached, apply herbicides according to the leaf stage of the weeds. 

Although many producers roll fields immediately after planting, some rolling does occur after emergence.  Rolling can help level the soil and push rocks into the ground making combining easier.  Research has shown that rolling soybeans after emergence does not reduce yields, but keep these points in mind:

1. Roll during the heat of the day to ensure that soybeans are limp.  Soybeans are the most turgid (stiff) during the morning hours, so rolling during this time will result in more plant injury.
2. Do not roll soybeans that are in the hook stage!  Soybeans that are just emerging out of the ground are more vulnerable to breakage.  Wait until all soybeans have fully emerged before rolling.
3. The best time to roll soybeans is during the unifoliate stage since all beans will have emerged by then.  Rolling can be completed successfully until the second-trifoliate leaf stage.  Waiting beyond the first-trifoliate will increase plant loss.

 

Forage
The weather has continued to be cooler than normal with adequate moisture.  This has slowed the development of alfalfa more than the grasses.  A key decision in any forage system is when to begin harvesting first-cut.  This should be dictated by three factors:

1. Feed quality required for your operation.  High producing dairy cows require forage high in energy and protein, but this would not be appropriate for over-wintering beef cows.
2. Number of cuttings required to get the combination of quality and quantity that you need.  Allow for 5-6 weeks re-growth between each cut, and count backwards from the beginning of the Critical Fall Harvest Period for your area.
3. Weather forecast.

Alfalfa weevil feeding has been evident in the south-west, but has not shown up yet in the cooler areas.  Scout your fields for small green caterpillars that skeletonize leaves at the top of the alfalfa plant (www.omafra.gov.on.ca/english/crops/pub811/5weevil.htm).  Harvest is the most effective management technique at this point. 

An excellent time to apply fertilizer is immediately following forage harvest.  With the increase in fertilizer prices, you may question whether you can afford this expense, but the cost to poor fertility is much higher than the cost of the fertilizer.  Target your fertilizer applications more strategically than in the past by taking soil samples after first-cut to guide fertilizer applications later in the summer. 

There have been some reports of boron deficiencies in alfalfa on sandy soils in areas that have been dry this spring.  If you can confirm that boron is low in the plant tissue, you should apply boron to the soil following first-cut.  Boron deficiency is most common in coarse, textured soils, particularly in central Ontario, and is aggravated by dry weather.  Refer to www.omafra.gov.on.ca/english/crops/pub811/5fert.htm#boron .

Pasture
Cool, damp conditions have resulted in excellent pasture growth.  The challenge now is to maintain forage quality and to keep them growing vegetatively so they will continue to produce through the summer.  Graziers should be clipping pastures as the livestock come off paddocks during this rotation, so pastures have a chance to re-grow evenly before the weather gets too hot and dry.  Grassy pastures should also receive nitrogen fertilizer.  Paddocks that are destined for hay harvest should already have been set aside so they can be harvested in a timely fashion.  The aftermath will then be available for grazing during the “summer slump”.

Winter Cereals  
Concerns over potential frost damage from the May 28th frost were unfounded.  While some heads are being trapped in the flag leaf ligule, and there is some flag leaf discolouration, the net impact will be negligible.
 
Early winter wheat has headed out.  Fusarium control products are being applied.  Risk for crops heading prior to June 4th is low due to cool weather.  Risk on later heading crops may increase significantly if warmer temperatures and rainfall prevail.  Assess your risk using www.weatherinnovations.com.

Rust has been found in Vienna wheat in multiple locations across the province.  All Vienna wheat should be sprayed with Folicur at fusarium timing to control rust.  FT Wonder and Carlilse should be scouted closely for rust as well (as should all wheat fields).  Isolated cases of other diseases have been reported, but generally disease levels remain low.  Disease control decisions must be made by late pollination (Day 5), as this is as close to harvest as any fungicide may be applied.

Spindle streak mosaic virus has been found in a number of fields.  The disease is the result of cool weather conditions and genetic susceptibility.  There are no effective control measures.  Warm weather (>18°C) will stop disease development, and some recovery is possible.

Armyworms have been found in several wheat fields in south-western Ontario.  Scout your fields!  Control is most effective when targeted to small larvae.  The threshold is four larvae per square foot.  Scout on cloudy days or evenings when larvae are feeding on the plant.  If control is required, spray in the evening or night, using high pressure and high water volumes.  For control options refer to OMAFRA Publication 812, Field Crop Protection Guide www.omafra.gov.on.ca/english/crops/pub812/p812toc.html.

Spring Cereals
Advanced fields are at Zadok Growth Stage 31 (first node), with many fields approaching Zadok 30 (leaf sheaths strongly erected).  Some herbicide applications were delayed beyond the optimum stage as growers waited for warmer temperatures.  Once the crop reaches Zadok 32 (second node visible), yield loss from weed competition has occurred, and significant herbicide damage to the crop may occur.  At this stage growers are better to wait, and use pre-harvest treatments if weed pressure will impact harvest.

Leaf disease pressure remains nearly non-existent in most spring cereals due to cool weather.  Continue to scout, and time fungicide decisions based on disease pressure.

Edible Beans
Wet weather has delayed planting of any significant acreage of edible beans.  If planting is delayed significantly, consider when beans will mature before continuing to plant a full season variety.  Late harvest can increase the risk of yield and quality losses.  Maturity date is important when winter wheat is to follow in the rotation.  It is always a good idea to retain seed tags and a small sample of seed to help resolve any emergence issues.  Good record keeping is important in IP production systems. The information is useful for referring back on cropping histories and is attractive to buyers as well.
.
If crusting or tight soils are a problem, be prepared to rotary hoe or perform crust busting while the crust is still soft.  When possible, this operation should not be performed on beans in the crook stage (just prior to emergence) until approximately three days after emergence.  Expect a 5-10% plant loss when using the rotary hoe.  Rotary hoeing during mid-day when bean plants are more flaccid (less turgid) will reduce stand loss.

Canola
Many early spring canola fields look excellent.  Early canola is now bolting and May planted canola is now in the 2-5 leaf stage.  Optimum weed control period is 2-4 leaf. Don’t lose yield caused by delays in herbicide application.  Canola can develop a new leaf every 3-4 days.  Flea beetle pressure has been low to date. Later planted fields should be monitored for flea beetles until the 4-leaf stage.  If you are considering applying a fungicide for sclerotinia, check product availability due to tight supplies.