Ontario Field Crop Report
July 16, 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
Harvest has begun.  Early yields are average, ranging from 50 to just over 100 bu./ac.  Lowest yields are often where armyworm damage has been severe and not controlled.  Quality is good with solid test weights and good falling numbers.  Fusarium levels have been within grade with occasional exceptions.  However, some samples are already coming in with a few sprouts and mildew downgrading to grade three.  Do not delay harvest!  Combines should roll as soon as wheat is below 18% moisture.

Take-all is rearing its head in many fields at much higher levels than normal.  Fields in a poor rotation (wheat on wheat, barley or grass hay) are most affected.  In severe cases, up to 20% of the field is showing injury.  In better rotations, sporadic plants infected can still be found.

The value of straw continues to be a hot debate in the countryside.  It is almost impossible to calculate the value of the organic matter return from straw, but mathematically, the value of four straw crops equates to a 0.1% difference in soil organic matter.  This increase in organic matter is the equivalent of 1.75” (44 mm) of available water holding capacity.  Conversely, if the value is calculated only on P and K removal, straw is worth 1.34 cents/pound (MAP at $1400/t, potash at $650/t).

Spring Cereals
The crop is well into grain fill.  Rust is prevalent in many oat and wheat crops, but is too late to control.  Spring wheat is showing significant purpling on the head in some fields, a condition called “melanism”.  This physiological condition is often confused with staganospora (septoria glume blotch), but can be identified by the lack of pycnidia (black pepper spots) in the discoloured area.  Melanism causes no yield loss.

Soybean Report
Condition of the Ontario soybean crop varies from average to excellent.  Some fields are suffering from water-logged soils.  Soybeans are in the R1 (beginning bloom) to R2 (full bloom) reproductive stages.  Fields have a full canopy unless they were planted late.  In most cases, plants now have a dark green colour as the root nodules have started to supply adequate nitrogen to the plant.  If fields are not turning dark green, scout the field to assess the problem. 

Phytophthera and rhizoctonia root rots are more prevalent this year due to excess rainfall.  Dead plants occur as a few in a row or as patches in the field.  Plants may also be stunted and yellow.  Selecting varieties with resistance and using cultural practices to reduce soil compaction has been shown to reduce the impact of root rots.  Improving soil structure and drainage will help to minimize problems for these diseases in the future.

Soybeans intended for identity preserved (IP) markets require field walks to ensure quality standards are met.  Weeds such as nightshade and pokeweed are of particular concern, as a few of these plants can cause severe staining of beans.  Tolerance to corn in IP soybeans or edible beans at harvest is zero.  Rogue fields for any off types.  In IP varieties that have a grey pubescence (hair on the stem), off types with a tawny pubescence should be removed.

Soybean cyst nematode (SCN) symptoms are now becoming evident in affected fields.  Scout fields for stunted, yellow plants.  SCN damage is often confused or misdiagnosed as potassium deficiency, herbicide injury, compaction, or root rot damage.  Do not simply pull up the plant to see SCN.  Dig up the plant, wash the roots carefully, and look for small white cysts the size of the end of a pen.  Under good growing conditions, visual damage from SCN may go unnoticed.  Manage using crop rotation and resistant soybean varieties once the problem has been identified.

Edible Beans
Early planted edible beans generally in good condition, are growing rapidly and are now beginning to flower.  Later beans on heavy soils are showing considerable yellowing mostly due to root rot caused by excess rainfall, variable soil conditions during tillage or planting operations, and soil compaction.  Emergence of late planted beans is good and is now at the first trifoliate stage.  No-till edible bean stands appear good with some reduction in stand due to high slug populations.  Leafhopper populations have been low to date. Striped flea beetles, an unusual pest of edible beans is causing some localized shot hole feeding damage.  Bronzing of unifoliate and lower trifoliate leaves from ozone and air pollution is evident in some stands.

There have been a few reports of common bacterial blight in white beans.  All bean types and varieties, except OAC Rico, are susceptible to common blight.  The disease is favoured by hot, humid weather (28-32°C) and spreads rapidly from infected plants by storms, people, animals, or machinery moving through fields when they are wet.  Control by copper based bactericides has been poor in controlling the spread of blight depending on disease severity and weather conditions.  Only with halo blight have these products been shown to be effective in reducing disease incidence.  The best success with these products occurs with repeated applications, with the first application made during vegetative stage prior to any sign of infection.  Fungicides have no effect in controlling bacterial infections.

Canola
Winter canola harvest is beginning this week with no yields reported.  Weevil damage to pods is high in fields where no control was applied.  Early planted canola has completed flowering with good pod set.  Cabbage seedpod weevils have mostly disappeared.  Swede midge damage is significant in some canola stands planted late May to early June.  Scout canola stands for diamond back moth and tarnished plant bug.  Diamond back moths were evident earlier than normal this year.  Populations are below threshold, but need to be monitored as there are several generations per year.  Diamond back moth larvae feed on leaves, flowers, and pods and can affect canola at all stages.  Threshold is 10-15 per square foot (1-2 per plant) at early flowering and 20-30 per ft2 (2-3 per plant) during early pod fill.  Tarnished plant bugs cause damage during pod fill, feeding on individual seeds. Hot, dry weather favours the insect.  Threshold for tarnished plant bug is 1-1.5 per sweep.

Corn
The majority of corn across Ontario appears to be in good shape with the earliest corn now in tassel.  On some heavy textured soils, corn is uneven due to excess moisture.  
Moisture is good to carry us through pollination so we anticipate good kernel set this season.

The strong storm fronts and persistent rain showers have been ideal for common corn rust  Common rust, along with northern leaf blight and gray leaf spot, are the most economically important corn leaf diseases in the province.  Unlike northern and gray leaf spot, which over-winters in Ontario, common rust spores originate each year from southern US/Mexico.  Frequent storm fronts from these areas have deposited spores relatively early this year when compared to the past few seasons.  

Growers need to assess their fields for leaf diseases as we enter the critical tasseling through to silking stage.  If you are considering a fungicide application for disease control, consider the following: susceptibility of the hybrid to disease, yield potential of the field, weather conditions and forecasts, fungicide costs, application method, and crop growth stage.  The primary purpose of fungicides is to protect leaves near the ear and above from significant disease.

Forage
July continues to be frustrating for those trying to make quality hay.  Many areas continue to have very limited opportunities to make hay without rain damage.  We are in a unique situation where there are considerable amounts of both first and second cut being made when weather conditions are suitable.  Supplies of “horse quality” first cut hay made without rain damage are quite limited in many parts of the province.

Be sure to monitor hay mows for heating.  Hay that is baled with very high moisture will heat rapidly.  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.  The critical time for spontaneous combustion is usually 2-3 weeks after the hay is put in the barn.  If you detect a slight caramel odour or a distinct musty smell, chances are you have a problem.  Check for heating by using a temperature probe.  Alternately, insert a copper or metal pipe into the mow.  If after an hour it is too hot to hold with bare hands, there is a severe problem.  Additional information on “Silo and Hay Mow Fires” may 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.  Propionate 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.  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 according to forage species, bale type, bale density, and whether a preservative has been applied.  Refer to “Preventing Mouldy Hay Using Propionic Acid” at www.omafra.gov.on.ca/english/crops/facts/preventing.htm