Ontario Field Crop Report
May 14, 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 Wheat
Warmer weather and good growth has improved the condition of the winter wheat crop in many areas. The early planted winter wheat is now at growth stage 39 (flag leaf fully emerged), about one week ahead of normal. The majority of the crop is at growth stage 32. There is more leaf scorch or herbicide burn on wheat from bromoxynil herbicides than normal.
Manganese (Mn) deficiency in the winter wheat is more common this year, likely driven by the changeable weather. Warm days encourage rapid top growth before root growth has a chance to catch up, showing more deficiency symptoms. Manganese deficiency symptoms appear as yellowing of the upper leaves, or a faint striping on the leaves. Much more diagnostic is the pattern of symptoms in the field. A common diagnostic for Mn deficiency is green tire tracks through the field where the compaction has decreased the aeration of the soil just enough to allow a little bit more Mn to dissolve. Foliar applications of manganese are preferred to correct a deficiency. Apply manganese sulphate to provide 2 lb/ac of actual Mn (8 lb/ac of product). Use high volumes of water (40 gal/ac), along with a spreader-sticker to improve coverage and uptake. The chelated forms of manganese have the advantage of being in liquid form and of tank mixing with most herbicides or pesticides, but they are much more expensive than the sulphate form. Very low rates of chelated product are not effective. For more information see the Agronomy Guide, Publication 811. http://www.omafra.gov.on.ca/english/crops/pub811/p811toc.html
Leaf disease pressure remains low due to the cool temperatures. No stands have reached threshold levels to warrant fungicide applications. Powdery mildew is the most prevalent disease, with higher pressure in susceptible varieties. Other visual symptoms such as cold temperature injury may be confused with disease. Correctly identify wheat growth stage for fungicide applications. Strobulurin fungicide products can be ground or aerial applied only up to flag leaf fully emerged stage (Zadoks 39). Do not apply at boot stage (Zadoks 47) and beyond because products that contain strobulurins have the potential to increase DON levels in the grain. Folicur 432 F can be applied only once per crop season. If it was applied for leaf disease control, it can not be used for Fusarium head blight control. In this case, Proline® 480 is the only option for Fusarium head blight control. Fungicide information is available in Field Crop Protection Guide, OMAFRA Publication 812. http://www.omafra.gov.on.ca/english/crops/pub812/p812toc.html
Spring Cereals
Planting is complete except in Northern Ontario. Most of the spring cereals are in the shoot to tillering stage (Zadok’s growth stage 13 to 21). Early fields show excellent emergence and early growth. The dry weather has kept the disease pressure very low to this point.
Scout fields for weeds. Broadleaf weeds have emerged with the cereal crop and should be sprayed between the 3 to 5 leaf stages of the cereals. No-till fields with heavy dandelion pressure should be sprayed with Estaprop (do not use on oats) for best control. Refer to “Guide to Weed Control”, OMAFRA Publication 75 to determine the product of choice for good weed control, and consult the product label for weeds controlled and application timing instructions. http://www.omafra.gov.on.ca/english/crops/pub75/pub75toc.htm
Corn
Corn planting is completed in many areas of the province and provincially it is estimated that 80% of the crop is planted. Some very limited re-planting has been done on early planted corn. Most of this re-planting is associated with cold temperatures (-8°C) that froze the shoot down to and including the growing point.
Crop Heat Unit (CHU) accumulation in the first 13 days of May has been 141, 118 and 141 for London, Waterloo and Ottawa respectively. Since it requires approximately 180 CHU for corn to emerge, many fields have been slow to come out of the ground. Most stands that have emerged look reasonable, with soils in some areas being tighter or blockier than usual. Keep an eye out for fields that might benefit from a pass with the rotary hoe.
Planting date trials have generally indicated that full season hybrids should be planted up to May 20-25. For the week following May 25, consider planting hybrids that are reduced by approximately 100 CHU’s.
Economic decisions around crop selection (corn versus soybeans) also come into play as we move into the second half of May. If you assume $5.25/bu for corn and $11.75/bu for soybeans and use OMAFRA estimates for cost of production, then 40 bushel/acre soybean yields generate the same revenue as 136 bu/acre corn yields. Factors such as farm yield averages, soil types, and crop rotation balance may become deciding factors. Both crops will normally experience yield reduction for delayed planting, but the penalty for corn over the May 25 to June 5 period is likely more severe than the penalty for soybeans.
Soybeans
Soybean planting has progressed slowly during the first half of May. Depending on the region, between 5% and 25% of soybeans were planted by May 15. Soybeans planted during the early part of May are now emerging.
No-till planting trials have shown that operating no-till coulters at three inches deep produces a one bu/ac advantage over no coulters or operating coulters at planting depth. Seeding depth was constant at one and a half inches.
A burndown herbicide treatment to eliminate emerged weeds is standard practice for no-till soybeans. Glyphosate burndowns should be applied 5-7 days before planting to ensure adequate translocation into perennial weeds. If annual weeds are the target, a three day pre-plant interval should be adequate. A burndown treatment is especially critical in conventional (non glyphosate tolerant) beans, because post emergent options are limited. If a pre-plant burndown in no-till soybeans was not applied, be careful not to apply glyphosate too close to emergence of conventional beans. Soybeans can emerge within 4 to 5 days of planting. In pre-emergent applications, apply glyphosate within three days of planting or before the beans start to crack the ground. If any soil cracking is evident, do not apply glyphosate! Wait until the conventional beans have emerged and use an early post-emergent spray.
Forage Report
Early planted new seedings are emerging well. These fields should be scouted for annual broadleaf weeds, such as lambsquarters. The risk of injury to alfalfa seedlings is greatly increased when 2,4-DB application is made outside of the first to the third trifoliate stage window. Note that page 102 in Publication 75, Guide To Weed Control has the incorrect product rate for 2,4-DB applied to underseeded cereals. The correct product rate is 0.7 to 0.9 L/ac when the formulation is 625 g/L. Field experience has demonstrated that reducing the rate of herbicide can reduce the risk of injury to alfalfa seedlings while providing acceptable suppression or control of weed seedlings.
Forage can be a heavy user of potash. An alfalfa-grass mixture yielding 4.5 tonnes/acre of hay equivalent removes about 900 lb/ac of K20 over three years. Without any fertilizer or manure, this can decrease the K soil test by about 45 ppm. Potash is important in promoting yield and persistence. Deficiency symptoms show up as small white dots concentrated at the margins of older alfalfa leaves. Soil test to ensure potassium levels are adequate. If the K soil test of the field is below 150 ppm, you can expect a response to add potassium. Consider top-dressing fields with commercial fertilizer or manure following one of the cuts during the summer.
Alfalfa weevil larvae have been detected feeding on new alfalfa growth in the south-west, so scouting should begin. Damage usually shows up first on areas that warm the quickest, such as south-facing slopes. Alfalfa weevil feeding damage starts as pinholes in the leaves and progresses to feeding between the leaf veins, resulting in a skeletonized appearance. Larvae are bright green with a distinctive white stripe down the centre of the back. Insecticides are only recommended when cutting is impractical, (i.e. when the alfalfa is in the pre-bud stage). Cutting before the bud stage can result in lower yields and extensive feeding damage to second-cut re-growth. Refer to OMAFRA Publications 812 Field Crop Protection Guide, and 811 Agronomy Guide.
Pasture Rotation
Early planted canola is now emerging. Begin scouting emerged canola for flea beetles. Populations can build rapidly under warm, sunny weather as flea beetles migrate in from field borders along fence rows and woodlots. Economic threshold for control is when 25% of plants show feeding damage.
Canola is slow to establish when in competition with weeds. Optimum time for weed control is the 1-4 leaf stage of canola. Trials have shown a 10% yield improvement by spraying at 1-2 leaf stage of canola versus the 5 leaf stage. Concentrate on controlling weeds that emerge with the canola, and less on weeds that come up after canola reaches the 4-6 leaf stage. Glyphosate is safe on Roundup Ready canola varieties from the cotyledon to the 6 leaf stage. A second application may be required to control subsequent weed flushes or to control perennial weeds.