Ontario crops recovering from spring frost
June 4, 2013, Ontario – Ground frost occurred in several parts of Ontario last week, resulting in discoloured corn leaves and frost injury to cereals in certain areas, according to the latest field crop report from OMAFRA.
The majority of canola has now been planted. Canola planted in last week is emerging in four to seven days. The frost on the weekend had minimal impact on emerged canola. Last week’s cold and wet weather limited flea beetle feeding. Seed treatments provide 2-3 weeks of protection, but flea beetles must bite the plant to die. Expect to see some leaf feeding damage. Foliar control is warranted as soon as you observe 25 per cent leaf damage prior to fourth leaf stage. Canola develops rapidly between first and sixth leaf stage. Control weeds early, prior to fourth leaf stage of canola to prevent yield reductions. When using Liberty herbicide, wild oats and volunteer cereals control is improved by use of a grass herbicide. Check canola populations and keep a record along with seeding rate to make adjustments for future years. Optimum stand is eight to 10 plants per square foot, but a healthy stand of four to five plants per square foot can yield close to full yield potential with management.
Frost injury is evident in a few fields in Kent County. Cereals have zero frost tolerance during the critical pollination stage. Only the earliest fields are affected, with the vast majority of the crop not quite at the susceptible stage. Recent rains have dramatically increased the risk for fusarium. Apply Caramba or Prosaro from day two to day four (day 0 = 75 per cent heads fully emerged). Use alternating turbo floodjets or forward/back nozzle configurations. Be sure to do an excellent job of tank clean out and flush boom end caps thoroughly. There can be tremendous leaf burn from fungicide/herbicide combinations or late N applications. Many growers continued to apply herbicides well after flag leaf emergence. Risks are greatly increased at this stage, and benefits greatly reduced. In future, consider fungicide applications only if proper weed control timing is missed. Earliest spring cereal fields are just reaching stem elongation. All weed control should now have been completed. Scout for disease and control if warranted.
Ground frost occurred across many parts of Ontario on May 25 and 26. As a result, corn leaves are discoloured and appear straw coloured to pale green to grey or black. In some cases, corn collapsed onto the soil surface. In most cases when the plant is at the sixth leaf stage or younger the growing point of the corn plant is below the soil surface and will not have been damaged by frost. This corresponds to V4 corn (four fully expanded leaves with leaf collars visible on the stem) or to seven leaf tips being visible. Most corn in Ontario was somewhere between emergence and sixth leaf stage during this cold period. Plants that have not had any injury to the growing point will generate new green tissue within three to five days. To examine the growing point more carefully, it is located about two centimetres below the soil surface and should be white or pale green and firm. Damaged growing points may appear grey and water soaked. Examination of the growing point will be more successful when two or three days have passed since the frost. Post emergent N applications using UAN flat fan nozzles should not be done once corn has passed the second leaf stage. Streamer nozzles cause little corn leaf damage when used up to the fourth or fifth leaf stage.
First-cut dairy haylage is underway in southern Ontario. Yields are quite variable. With the cooler weather, grass maturity is more advanced than alfalfa. Frost damage to alfalfa seems minimal. Applying liquid manure immediately after alfalfa harvest improves both yield and forage quality ( http://www.omafra.gov.on.ca/english/crops/field/news/croptalk/2007/ct-0307a5.htm). Respiration, harvest, fermentation, storage and spoilage losses are very real and very costly, although largely invisible to us. Rapid wilting with wide swaths minimizes respiration losses. Reducing fermentation dry matter losses (shrink) and improving bunklife and forage quality by using a research proven haylage inoculant easily pays (Silage Inoculants FieldCropNews.com). Fill, pack, cover and seal horizontal silos quickly. Pack in thin layers (less than 15 centimetres) with adequately sized tractors for sufficient packing time per tonne. Cover with an oxygen-barrier film and silage grade (UV protection) six-millilitre plastic. Avoid rainwater draining off the plastic down the wall into the silage to avoid nutrient leaching and butyric acid in the bottom and corners of the silo..
Most cool season grasses have headed. For optimum growth and forage quality the grass should be grazed before maturity advances. Quick rotations will help to maintain good quality forage. Consider harvesting one or more paddocks as hay/baleage if you have more mature forage than the livestock can graze. These paddocks will then be at the proper grazing stage in about three to four weeks. Annuals for summer grazing should be planted during early June for grazing in August. Remember that it is the rest and recovery period that grows more pasture. “Take half and leave half” on each rotation is a big step to optimizing pasture yields.
Rain and warm temperatures have resulted in fast emergence and vigorous early season growth. The seedbed was dry in some regions at planting time, leaving seed in dry ground. Those areas now received moisture so plant stands are expected to be good. Frost damage was limited as most fields had not emerged yet when the frost hit. For fields that were emerged, if frost damage penetrated below the cotyledons they will not recover. If the top of the plant is destroyed but not the stem portion below, the plant will send out new shoots from the base of the leaves or cotyledons. It usually takes three to five days to see if new growth will emerge. If plants survive there is no yield loss associated with early season frost unless the plant stand has been substantially reduced. Soybeans can tolerate -2.4 C for up to four hours before they are destroyed.