Ontario Field Crop Report
June 18, 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.
Soybeans
Soybean planting is essentially complete. Despite the slow start, emergence has been good to excellent. Soybeans tend to be in the first to third trifoliate stage. For acres not planted, increase the seeding rates by 10% which will help to increase the height of the lowest pods and the number of pods per acre. Narrow rows are recommended for late planting dates.
Bean leaf beetle feeding has been found in many areas but damage has been minimal. A small amount of leaf feeding does not impact yield. Adult bean leaf beetle have successfully over wintered further north and east this year and are in fields that do not normally experience early season infestations. Scout early planted fields, especially those that did not have insecticide seed treatments. Leaf feeding may raise concern but soybeans can compensate. Insecticide application should not be based solely on the appearance of leaf feeding. The insecticide application threshold is 16 beetles per foot of row (52 beetles/metre of row) up to the V3 stage (3-4 beetles per plant) and if plants are being clipped off. Control measures are only necessary when the plant is not able to stay ahead of feeding damage and newly emerging leaves are significantly damaged. Research from Iowa State indicates that spraying for these over wintered bean leaf beetles may promote soybean aphid infestations later in that field because natural predators are killed by the insecticide treatment.
Soybean aphids have been detected in a number of fields, though the incidence remains low and is normal for this time of year. Predators are already present in fields and typically reduce these early aphids significantly. Weekly scouting for aphids should start by early July. Early planted fields should be scouted once before the end of June to ensure that aphids blown in from the U.S. in high numbers do not go undetected.
Wet field conditions have been the greatest challenge to post-emergent weed control. Good growing conditions and thorough spray coverage with high water volumes will make it easier to control larger weeds. Where re-spraying is necessary, wait for weed re-growth to begin as weeds that are stressed or not actively growing are much harder to kill.
Spring Canola
Canola stands in most areas are excellent. April planted canola is now at the bolting to first flower stage. Cabbage seedpod weevil is evident in many fields at below threshold levels. Insecticide is necessary at thresholds of two weevils per sweep. Spray application should be done at the 10-20% bloom stage (2-4 days after flowering starts) to control the weevils before they lay eggs on the pods. Apply insecticides after 7:00 p.m. when bees are not foraging, or if this is not possible, before 7:00 a.m.
The risk of sclerotinia (white mould) is high in canola that is now beginning to flower. High levels of infection can reduce yield by 25-30% in addition to causing quality losses. Factors that increase the risk for white mould include a dense crop canopy, showery weather with moderate temperatures (below 25°C) during flowering and saturated soil in the two weeks before flowering. To be effective, initial fungicide application should occur at 20-50% bloom. 20% flower occurs when there are 14-20 open flowers on the main stem, about five to six days after flowering begins. Fungicides act as a protectant and must be applied prior to infection and cover as many flower petals as possible before drop.
Edible Beans
Edible bean planting is 80-95% complete in the southwest, and 10-80% complete in other areas. Emergence has been uniform in most fields, with root rot now evident in some fields. Leafhopper populations have been low to date, but can explode overnight now that forage harvest has begun. Leafhopper adults are carried into Ontario on storm fronts from the USA. Cruiser treated seed should provide leafhopper control for 4-7 weeks after planting.
Wait until beans have at least one trifoliate before applying postemergent broadleaf herbicides such as Basagran and Reflex. These products act primarily by contact and it is essential to achieve good coverage by following recommended water volumes and ensuring ample canopy penetration.
Forages
Wet weather has delayed haying in many parts of the province and forage quality is decreasing quickly with advancing maturity. A considerable amount of hay has been rain damaged. Wrapping baleage and using propionic acid are options to consider. Wrapping large haylage (baleage) reduces weather risk, but must be managed to reduce spoilage. Make firm, dense, uniform bales. Large squares are usually denser than round bales.
Bale at 40-55% moisture. Lower moistures can work, particularly with large square bales wrapped with adequate plastic, but are at a greater risk of spoilage. Use enough plastic! Bales should be wrapped air-tight with a least 6 mils of plastic film (six wraps of 1 mil or four wraps of 1.5 mil). To ensure against tearing, 8 mils is preferable, particularly with drier baleage. Wrap round bales within two hours of baling on hot days and within 4-12 hours at cooler temperatures. Large square bales can withstand later wrapping. Avoid using hay that was rained on. Avoid raking to minimize contamination by clostridia bacteria. Do not incorporate soil into the windrow with the rake. Avoid fields where manure has been applied and mature hay with low sugar content. Be sure to repair all tears and holes in the plastic. Refer to “Maintaining Quality in Large Bale Silage” at http://www.gov.on.ca/OMAFRA/english/crops/facts/98-069.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. Basic application systems with a tank, pump and nozzles can be mounted on balers relatively inexpensively. Systems with computerized in-line moisture sensors and automatic on-the-go flow regulators are also available. 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.
Corn
The persistent rains across much of the province are making it difficult to complete competing weed control and nitrogen side dress operations. Many fields are yellow due to cool wet weather or from late control of weeds. Don’t skimp on nitrogen rates in fields where weeds were controlled late. If still attempting to side-dress tall corn, consider a “skip row” application to reduce field tramping and horsepower requirements.
The critical weed free window ends at roughly the 8-leaf stage in corn. Weeds that have emerged prior to the 8-leaf stage must be controlled to reduce competition and yield loss. Weeds that emerge after the 8-leaf stage generally result in less than 5% yield loss and spraying is usually not justified.
Spaying at the 8-leaf stage may require some additional precautions around weather conditions, herbicide selection and crop safety. Preliminary research at the University of Guelph, Ridgetown Campus, indicates that when spraying to control grassy weeds beyond the 8-leaf stage crop safety was impacted least with Accent and Option. For broadleaf weed control beyond the 8-leaf stage, Callisto + atrazine and Pardner + atrazine were observed to have the least crop injury when compared with other standard herbicides. Yield losses from these late applications are likely to have occurred because of weed competition prior to control.
As the wheat crop matures or when it has been stripped of its leaves, armyworm will move into neighboring corn fields. Corn can outgrow armyworm injury since the growing point is not targeted. Monitor the perimeter of corn fields bordering wheat to determine if control is necessary. Armyworm feed mainly at night so it is best to scout during the evening hours or very early morning. During the day, you may find the larvae in the whorl, leaf axils, amongst the crop debris on the soil surface or under soil clods. The threshold for control is two or more, 2.5 cm (1 inch) or smaller larvae per seedling and feeding damage exceeds 10%. For corn past the whorl stage, consider applying insecticide if 50% of the plants are showing damage and are infested with larvae at or smaller than 2.5 cm (1 in.) in size. Spraying headlands adjacent to wheat fields may be sufficient to prevent the infestation from moving into the rest of the corn field.
Winter Wheat
Most of the winter wheat crop is now in early milk to soft dough stage. Armyworms have been found in many parts of southwestern Ontario above threshold levels and should be sprayed as soon as possible. Scout to determine the number and size of the armyworms. Look deep into the canopy as the smaller armyworms tend to feed on the lower part of the plant and hide at the soil surface. Control is warranted when there are four unparasitized armyworm larvae, smaller than 4 cm (1½ in.), per square foot or if head clipping is occurring. Examine 20 plants from five locations in your field to determine the level of infestation. Record the size and number of larvae. When scouting, check the backs of armyworms for parasite eggs. These small, oval, yellowish eggs are usually located just behind the larva head. These are eggs of a parasitic fly whose maggots will kill the armyworm larvae. If there are other grass type crops such as corn or grass hay fields nearby, the armyworms will ‘march’ over to the next crop.
Spring Cereals
Most of the spring wheat is at growth stages 37-47 (flag leaf to head in boot). Early seeded spring wheat and barley are now in head. It is too late to spray spring cereals for weed control. Some herbicides if applied at this stage and coupled with trampling, will result in yield loss. If weed pressure is heavy, plan to use a pre-harvest burndown. If the cereals are under-seeded, consider harvesting the cereal crop as a silage/baleage crop to prevent the weeds from going to seed and competing with the new forage seedlings.
Leaf disease pressure in spring cereals is surprisingly low given the continuous showers. The main leaf diseases present are powdery mildew and septoria leaf spot on wheat, net blotch and scald on barley, and some septoria leaf spot on oats. Note that Headline EC and Stratego 250 EC can be applied up to flag leaf fully emerged stage (GS 39) while Tilt 250E up to before head is half emerged (G.S. 49-55) and Bumper 418 EC can be applied up to just before the head is half emerged stage (GS 55).
Start to monitor spring wheat for fusarium risk on the Fusarium Risk Maps available at: http://www.weatherinnovations.com/fusariumeast.cfm. Knowing your heading date is critical to predicting disease development. Day zero is when 75% of the heads have fully emerged above the flag leaf. More information is available on this website. The field specific component of DONCast is free this year. Since it takes one to two days for base information to be uploaded, get your information in now. Then “what if” scenarios can be run instantaneously and you can determine the actual fusarium risk to your wheat at heading time.
Scout for armyworms which can cause significant feeding damage in spring cereals (see comments in the winter wheat section).