Sunflowers are physiologically mature at the stage R-9. At this stage, the seeds have reached maximum size and bushel weight. Visually, this is when the back of the head is yellow and the bracts are brown. Timing of desiccation is important as application to early can result in decreased seed size and test weight.
Coverage is also important to increase the speed and consistency of dry-down. Using the water volumes suggested by the manufacturer will provide the good coverage over the back of the heads. In addition to coverage, daytime temperatures above 20-25C will assist in faster and more effective dry-down of the pulpy tissue in the head and assist in earlier combine operations.
Refer to the Guide to Field Crop Protection for products and rates registered for sunflowers.