If canola is not drying down after a Reglone application, the following may provide some insight as to why:
Reglone is a contact herbicide (only kills what it contacts) and is registered in canola to dry green material to facilitate harvest. “Contact” means that only the parts of the plant that are contacted by the spray solution will be desiccated. Coverage is the key to good activity.
Some parts of the plant will still remain untouched even with the highest water volumes. Reglone is activated by light reactions in the plant, so applying in darkness allows the active ingredient to move deeper into plant tissues before being activated. Applications made in bright sunshine are active as soon as the spray hits the leaf surface and any further spread is immediately stopped. To allow the Reglone to spread as far as possible within the plant before activation, apply under cloudy conditions or in the evening.
The Reglone label says to wait 7 to 10 days before combining canola and mustard, but do not wait longer than 14 days. The herbicidal activity of the Reglone will occur quickly, within minutes of the treated plant’s exposure to sunlight, and continue for a few hours. This is evident by the water soaked appearance of treated plant surfaces shortly after application, as the liquid contents of the plant’s cells leak from ruptured membranes. In the following 7 to 10 days, the tissues affected by the Reglone application will continue to dry. Reglone is unlikely to provide any additional desiccation benefit beyond 10 days. Continuing to wait for further desiccation from this application will likely just put the pods that were desiccated at risk of shelling.