Ontario Field Crop Report
July 3, 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

The majority of the corn in the province made the proverbial “knee-high” by July 1 and is in good condition.  In some pockets of the province, the corn crop is variable and suffering from too much rainfall.  We have grown accustomed to conditions in the past few years where corn development has been significantly ahead of this year.  Crop heat units (CHU) accumulation for June was 709 and 700 at London and Ottawa respectively. From May 1 to July 1, both locations are only slightly behind (3-5%) normal in terms of CHU accumulation.

Hail damage has been reported at a number of locations.  The OMAFRA Agronomy Guide indicates that if 40% leaf defoliation occurs at the 12 leaf stage yield loss estimates are 3-5%.

Delayed weed control due to wind, rain or competing activities has meant that a significant number of fields have depressed corn growth due to weed competition.  Wisconsin research would indicate that fields with delayed weed control (weeds controlled at 30 cm height) required more additional nitrogen than clean fields.  If the original amount of nitrogen applied was according to the OMAFRA nitrogen calculator, then sidedressing an additional 50 kg N/ha may be a reasonable option.

Soybean Report

Soybeans are in the first to third trifoliate leaf stage.  Most soybeans are rapidly filling the canopy and are now turning a dark green colour.  Some fields remain pale green or yellow.  Pale green soybean leaves at this time of year can be caused by a lack of nitrogen in the plant.  As bean leaves are growing in these early stages the roots are not able to supply all the nitrogen required.  A dark green colour will return as the nodules catch up and supply the N required by the leaves.  Nitrogen fixation does not start in earnest until the 2nd to 3rd trifoliate.  Excess moisture and cooler weather this year has slowed N fixation and prolonged the normal pale green stage of the crop.

If the yellow beans are concentrated on headlands or where there has been obvious glyphosate spray overlap on RR beans the culprit may be yellow flash.  Yellow flash sometimes occurs with the application of glyphosate and glyphosate tankmixes.  These symptoms usually last for about a week and no yield declines will result. 

Yellow leaves with dark veins are classic symptoms of true Mn deficiency and will cause yield losses.  The key to identifying this problem is that the leaf veins remain a dark green while the areas between the leaf veins are yellowing.  If caught early enough, it can be completely corrected by a foliar application of manganese. 

A few isolated fields received hail damage.  Plants can often recover as long as the stem is intact up to where the cotyledons were attached.  It generally takes at least 4 to 7 days before a good assessment of a field can be made unless the damage is extreme.  If hail damages the growing point of the seedling, but not the stem portion below, the plant will send out new shoots from the base of the leaves or cotyledons. Those plants damaged below the cotyledons by early-season hail will not recover.  Research trials show that leaf loss at early growth stages has little impact on final yield or maturity.

Canola

Early canola fields are near finished flowering while later fields are generally at the end of the optimum window for sclerotinia fungicide application.  No sclerotinia has been reported.

Cabbage seedpod weevil populations have dropped dramatically, an indication that the first generation weevil adults is near the end of their life cycle.  Weevil populations in canola were generally below the action threshold of 2-4 adults/sweep, with the occasional field above. 

Canola in late flowering to early green pod stage should be scouted for alternaria black spot disease.  Alternaria has not been a problem in Ontario canola fields in the past, but has been know to cause yield and increased shattering losses.  The disease is favoured by showery cool weather or heavy frequent dews during pod fill.  Look for brown to black circular spots on leaves or pods.  The risk is higher in lodged canola. There is no established threshold.  A side benefit to fungicides applied for sclerotinia is that they also provide suppression of alternaria during the flowering period, but won’t control later infections.  For further information refer to OMAFRA Agronomy Guide.

Low populations of diamond back moth larvae are present in many canola fields.  The small green larvae feed on leaves and pod tissue.  Later generations cause the most damage when populations may be higher.  Scout fields during pod fill.  

Edible Beans

Planting is 95% complete provincially, with planting completed in northern areas, but southern areas still struggling to finish.  Emergence has been good, with some damage from local pounding rains and hail.  Leafhopper populations have been low, but this can change quickly now that much of the first cut forage is occurring and with warmer dry weather in the forecast.  In fields planted with seed treated with cruiser insecticide, leafhopper control should last 4 – 7 weeks following planting.  The leafhopper threshold at first flower is 2 leafhoppers per trifoliate.
Bean leaf beetle have been increasing in dry bean fields the past few years and low levels of leaf feeding injury can now be seen.  Early leaf feeding damage appears as small round holes between veins.  No threshold is established but other jurisdictions use a threshold of 50% leaf loss or 3-7 per sweep in early vegetative stage.  Feeding damage during pod fill is more important stage, when newly emerged beetles feed on foliage and pods.  Slug feeding damage is occurring in no-till fields.

Forages

June has been frustrating for those trying to make quality hay, with some areas reporting some rainfall every day of the month.  There is still significant first cut waiting for dry conditions to be harvested.

Hay that is baled at too high a moisture will heat rapidly.  It is important to check hay mows for heating.  The critical time for spontaneous combustion is usually 2 to 3 weeks after the hay is put into storage.  Heating occurs from the rapid growth and respiration of mould and bacteria.  If the moisture and heat cannot dissipate, high temperatures build and are self-sustaining.  Even low amounts of heating can result in dusty hay with reduced feed quality and palatability.  If severe, heating can result in a barn fire.  Be sure to monitor hay mows for heating.  If you detect a slight caramel odour or a distinct musty smell, chances are you have a problem.  Check for heating by using a probe or an iron or copper rod.  If after an hour it is too hot to hold with bare hands, there is a problem.  A forage analysis with a high ADF-N value will indicate heat damage.  Additional information on “Silo and Hay Mow Fires” can be found at http://www.gov.on.ca/OMAFRA/english/engineer/facts/93-025.htm

Buffered propionic acid preservatives can assist in preventing mould when baling “tough” hay.  Propionic acid is an organic acid that acts as a fungicide, inhibiting the growth of moulds while the bale dissipates moisture in storage.  Follow product label directions.  Use the correct application rate according to the percent moisture of the hay.  Since large square bales are denser, they require more acid than other bale types of similar moisture.  Moisture tester accuracy will influence whether or not the application rate is adequate.  Probe-type hand-held electronic moisture testers can be subject to some error and should be calibrated.  Forage species, bale type, acid and bale density can influence readings. Refer to “Preventing Mouldy Hay Using Propionic Acid” at www.omafra.gov.on.ca/english/crops/facts/preventing.htm

The horse hay market requires hay that has not been rained on, is green and weed free.  With good conditions for forage regrowth, some producers are considering harvesting second cut from fields with high percentage of grass.  Hay fields with less than one third legumes will benefit from the application of up to 100 kg/ha of nitrogen to improve yield and quality.

If alfalfa weevil populations were high in a late first cut, occasionally surviving larvae can feed on regrowth.  The characteristic symptom is regrowth not ‘greening up’.
Slug populations are higher than normal in most crops including winter wheat stands.  Where summer seeding is being considered after wheat harvest, scout the wheat now for slugs.  If slug populations are high in the wheat, some tillage will be beneficial ahead of forage seeding.

Consider clipping pastures that have an abundance of plants with seed heads or weeds coming into flower.  Clipping will stimulate new grass growth and reduce the seeds produced by the weeds.  Clipping height should be at least 10 cm (4 inches) or higher to assist in stimulating new growth in the forages.

Cereal Report July 2, 2008
Winter Cereals:  
Harvest will begin in the southwest as soon as the weather allows.  Growers should be prepared to harvest as soon as possible.  Research proves that test weight drops the longer wheat remains in the field, thus early harvest is essential for top quality grain.

Fusarium continues to show as fields approach maturity.  Advanced fields are beyond visual assessment.  Growers should scout fields, and note heavily infected fields versus cleaner fields.  If at all possible, heavily infected fields should be harvested and stored separately.  This allows decisions to be made after harvest as to the best management for the grain.  Blended grain simply cannot be separated after harvest.  Check fields after corn or highly susceptible varieties first (see www.gocereals.ca ), as they are the most probable candidates for high fusarium levels.

It is also essential to clean and prepare bins for new grain prior to harvest.  Wheat is one of the toughest crops to store, both because it is harvested in the summer when temperatures are high, and the fact that insect pests seem more attracted to wheat.  Start with total and proper sanitation, removing all old grain and dust if possible, including lifting aeration flooring.  After sanitation, spray the inside and outside of the bin with a diametaceous earth product, to provide a “seal” or protective barrier to insect infestation. 

As the crop matures, many other diseases are beginning to appear.  Both stripe rust and stem rust have been identified in the crop, as well as staganospora (septoria glume blotch).  It is too late to do any further management to control these diseases.
 
Spring Cereals:  Late fields are heading, with early fields well into grain fill.  The risk for fusarium remains high, and growers should consider a fungicide for fusarium control on spring wheat fields just now heading, as long as yield potential looks good.  Unfortunately, experience dictates that the benefit of fusarium control in spring wheat is much less than in winter wheat.

Heading is the last opportunity for leaf disease control products, without invading pre-harvest interval timelines.  Disease pressure is high in many fields and crops.  Rust is prevalent in oat, scald is significant in barley, and spring wheat is showing heavy mildew pressure in susceptible varieties.  A range of other diseases can also be found.  Growers needing good quality grain for specific end use markets should scout fields, and use a foliar disease to control diseases if present in these fields.
Cereal leaf beetle can be found in most fields, as well as slug damage.  However, damage is well below threshold levels, and control of these pests is not warranted.