Applied nitrogen varies from region to region, but significant progress has been made over the last week. Estimates range from < 50% to 75% of acreage having received an application of nitrogen. Some producers that have pushed higher nitrogen rates (150 lbs N/acre) last year have opted to cut back this year by 20-30 lbs N/acre. This has been prompted by both the cost of nitrogen and increased lodging risk. The most advanced wheat in the province is at growth stage 30 (stem elongation).
Plant Growth Regulators:
Plant growth regulators (PGRs) were discussed this week, since wheat fields will soon be approaching the optimal growth stage for application. Proliant should be applied prior to growth stage 31(1st node detectable). Ideal timing for Moddus is growth stage 30-32 but the window for application stated on the label extends to growth stage 39 (flag leaf). If temperatures the day before application of Moddus were below 3-5°C it is best to apply the PGR alone and you may want to wait for warmer weather. When additional products are added to the tank there is more risk of crop injury. If a tank mix is planned, use higher water volumes (e.g., 20 gal/acre, 200 L/ha).
It was asked whether it’s a good practice to do 3-way mixtures of herbicide, fungicide and growth regulators. Generally, the more products you put in the tank, the greater the risk of injury and incompatibility. Additionally, the ideal crop and pest staging for each operation does not often coincide at the same time and separate applications would improve the effectiveness of each product. However, workload and environmental conditions may push you to use a 3-way mixture. Make sure you read each label to ensure that mixing is not restricted, talk to the product manufacturers to glean any best practices and ensure that you use high water volumes and spray under favourable environmental conditions.
Herbicide resistant Waterhemp:
Waterhemp populations resistant to group 27 herbicides (e.g. Callisto) have been confirmed in 7 Ontario Counties (Chatham-Kent, Elgin, Essex, Lambton, Middlesex, Northumberland, The United Counties of Stormont, Dundas and Glengarry). This means that populations of waterhemp exist that are resistant to 5 different herbicide modes of action. Fortunately, many soil applied herbicides still provide effective early season control of this weed.
An ongoing “integrated weed management” study conducted by the University of Guelph (Ridgetown Campus) has demonstrated that the best approach to managing waterhemp and minimizing its production and dispersal of seed requires the following approach:
- Plant a diverse crop rotation.
- Establish competitive cover crops after harvest, mow or clip if necessary to reduce seed production of any emerged weeds.
- Use effective soil applied herbicides with multiple modes of action.
- Plan on a second herbicide application to control later emerging seedlings