Desiccation: How, When and Why?
Natural desiccation can be slow and uneven. Poor weather can cause reduced quality and yield through stem breakage, shattering and predation by blackbirds. To speed up the natural desiccation process, it may be worthwhile to consider the use of a chemical desiccation. Chemical desiccants are generally typical herbicides that have achieved special registration to be used as a harvest aid.
What is the right STAGE to desiccate at?
Timing of desiccation is critical as application prior to physiological maturity can result in decreased quality, seed size and test weight. 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 and seed moisture is between 30- 35%.
What PRODUCTS are registered as a Harvest Aid?
There are currently three products, Reglone (Syngenta), Desica (Syngenta), and Heat (BASF), registered as a Harvest Aid for sunflowers. Both of these products can be applied by air. The application rates for the products is as follows;
- Preharvest Interval for Reglones and Desica is 15-20 days.
- For best results with Reglones and Desica apply in the evenings or on a cloudy day for best results.
- Preharvest Interval for Heat is 7 days
- For all products high water volumes are needed for proper efficacy.
- The above products may have slightly different timing ranges. Consult the label or chemical representative for more details.
Coverage is critical when desiccating sunflower. This is because the back of the head of sunflower is so pulpy that improved coverage will increase rate of dry-down. Applying at the water volumes as suggested by the chemical companies will achieve the required coverage for desiccation. However, water volumes may be lower than desirable during application. If the application is timed when there is free water or dew on the plants, the products will spread‘ on the dew, resulting in a better desiccation. If activity in the plant (so after application) occurs when temperatures are above 20-25C, this will also aid in faster and more efficient desiccation and dry-down.Click here for the full bulletin.